Georgia-Florida SKYWARN

Friday, April 20, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 201224
SWODY1
SPC AC 201222

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0722 AM CDT FRI APR 20 2007

VALID 201300Z - 211200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM CENTRAL SOUTH DAKOTA SWD
TO NWRN KS...

..SYNOPSIS...

NEXT IN A SERIES OF POTENT S/WV TROUGHS DIGGING SEWD JUST OFF CA
COAST WITH DOWNSTREAM TROUGH RIDING NNEWD INTO SRN CANADA OVER THE
RIDGE IN THE CENTRAL CONUS. LEE TROUGHING E OF CENTRAL ROCKIES
CURRENTLY WILL INTENSIFY THROUGH THE AFTERNOON WITH CURRENT WEAK LOW
CENTER SERN CO SHIFTING INTO NEB PANHANDLE BY THIS EVENING.

LOW LEVEL MOISTURE SPREADING NWD E OF SURFACE TROUGH WITH DEWPOINTS
RISING INTO THE MID 50S NWD INTO WRN NEB BY THIS AFTERNOON. SURFACE
TROUGH/DRY LINE FROM CENTRAL TX PANHANDLE NWD ALONG KS/CO BORDER
WILL MIX A LITTLE E BY THIS AFTERNOON... RETURNING POSSIBLY AS FAR W
AS EXTREME CO BY THIS EVENING AS UPPER SUPPORT REMAINS WELL TO THE W
THROUGH THE FORECAST PERIOD.

..HIGH PLAINS...
VEERING SHEAR PROFILES...STEEP LAPSE RATES AND INCREASING LOW LEVEL
MOISTURE/INSTABILITY PROVIDE FOR A CONDITIONAL THREAT OF SUPERCELL
DEVELOPMENT BY MID/LATE AFTERNOON VICINITY LEE TROUGH/DRY LINE.
THERE WILL BE A LACK OF MID LEVEL COOLING AND UPPER SUPPORT ACROSS
THE DRY LINE TODAY AS THE CA TROUGH NOT EXPECTED TO BE A FACTOR
UNTIL SAT. THUS SURFACE INITIATION WILL BE TIED TO CONVERGENCE
VICINITY DRY LINE AND SURFACE HEATING.

MODEL GUIDANCE DOES SUPPORT AT LEAST A FEW SURFACE BASED STORMS
VICINITY CO/KS BORDER WITH A LITTLE GREATER THREAT INTO WRN NEB.
ANY STORMS THAT CAN DEVELOP COULD QUICKLY DEVELOP INTO A RELATIVELY
HIGH BASED SUPERCELL. PRIMARY THREAT WILL BE VERY LARGE HAIL THRU
THE EVENING WHEN SURFACE BOUNDARY LAYER SHOULD BEGIN DECOUPLING.
AMOUNT OF PRECIPITABLE WATER OF LESS THAN 3/4 INCHES SHOULD LIMIT
THE OVERALL STORM COVERAGE.

MORE WIDESPREAD THUNDERSTORMS EXPECTED OVERNIGHT NWD THRU THE
DAKOTAS AS INCREASING WARM ADVECTION ON 40-50KT LOW LEVEL JET
PROVIDES FAVORABLE LIFT. THESE STORMS SHOULD BE ROOTED WELL ABOVE
THE SURFACE...BUT GIVEN THE STEEP MID LEVEL LAPSE RATES AND
SHEAR...ROTATING STORMS AND ASSOCIATED MARGINAL SEVERE THREAT
EXPECTED...PRIMARILY LARGE HAIL.

.HALES/GRAMS.. 04/20/2007

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DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 200829
SWOD48
SPC AC 200828

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0328 AM CDT FRI APR 20 2007

VALID 231200Z - 281200Z

--ORGANIZED SEVERE WEATHER EPISODES WILL BE POSSIBLE OVER THE
SRN/CNTRL HIGH PLAINS MONDAY...APRIL 23RD...THE SRN/CNTRL PLAINS
TUESDAY...APRIL 24TH AND THE ARKLATEX INTO LOWER MS VALLEY
WEDNESDAY...APRIL 25TH.--

..DISCUSSION...

DESPITE SLIGHT DIFFERENCES IN TIMING...LATEST MEDIUM RANGE GUIDANCE
IS RELATIVELY CONSISTENT IN INTENSIFYING UPPER TROUGH OVER THE
ROCKIES ON DAY 4 /APRIL 23RD/...SHIFTING IT E INTO THE CNTRL/SRN
PLAINS ON DAY 5 /APRIL 24TH/...AND THEN DEAMPLIFYING IT AS IT
TRANSLATES EWD THROUGH THE REMAINDER OF THE EXTENDED PERIOD.
VERTICAL SHEAR WILL CORRESPONDINGLY INCREASE ACROSS A SUFFICIENTLY
MOIST WARM SECTOR SUCH THAT IT APPEARS THAT MULTIPLE SEVERE STORM
EPISODES WILL BE POSSIBLE.

THE GREATEST SEVERE WEATHER POTENTIAL APPEARS TO BE ON
MONDAY...APRIL 23RD OVER THE CNTRL/SRN HIGH PLAINS...TUESDAY...APRIL
24TH OVER THE SRN INTO CNTRL PLAINS AND THEN ON WEDNESDAY...APRIL
25TH OVER THE ARKLATEX INTO LOWER MS VALLEY. THEREAFTER...SOME
SEVERE WEATHER POTENTIAL WILL EXIST ALONG THE CNTRL/ERN GULF
COAST...THOUGH UNCERTAINTY IN EVOLUTION OF SYNOPTIC SYSTEM IS SUCH
THAT NO ADDITIONAL DAYS WILL BE DELINEATED.

.MEAD.. 04/20/2007

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 200714
SWODY3
SPC AC 200713

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0213 AM CDT FRI APR 20 2007

VALID 221200Z - 231200Z

..THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE MID AND
LOWER MO VALLEY INTO UPPER MIDWEST...

..SYNOPSIS...

LATEST MODEL GUIDANCE IS IN GOOD AGREEMENT IN INDICATING THAT
NEGATIVELY TILTED MID-LEVEL TROUGH INITIALLY OVER THE CNTRL PLAINS
SUNDAY MORNING WILL DEAMPLIFY AS IT TRANSLATES NEWD INTO THE GREAT
LAKES...CRESTING RIDGE AXIS IN PLACE OVER THE ERN STATES. IN THE
LOW-LEVELS...PRIMARY SURFACE LOW OVER NERN SD IS EXPECTED TO DEVELOP
NEWD INTO CNTRL ONTARIO WITH A SECONDARY WAVE DEVELOPING ALONG
TRAILING COLD FRONT FROM S-CNTRL NEB INTO WRN WI BY MONDAY MORNING.

..MID/LOWER MO VALLEY INTO UPPER MIDWEST...

TSTMS /SLIGHTLY ELEVATED/ ARE EXPECTED TO BE ONGOING SUNDAY MORNING
ALONG FRONTAL ZONE FROM NRN MN SWWD THROUGH ERN SD INTO CNTRL
PORTIONS OF NEB/KS. SOME HAIL WILL BE POSSIBLE WITH THE MORE
INTENSE STORMS INITIALLY...ESPECIALLY THOSE OVER KS INTO NEB IN
CLOSER PROXIMITY TO UPPER TROUGH WHERE BOTH INSTABILITY AND FORCING
FOR ASCENT WILL BE STRONGER.

ADDITIONAL...SURFACE-BASED STORMS WILL INCREASE ALONG COLD FRONT BY
EARLY AFTERNOON OVER ERN PARTS OF SD/NEB INTO WRN MN/IA...PERHAPS
SWD INTO NERN KS AND NRN MO WITHIN MARGINALLY TO MODERATELY UNSTABLE
AIR MASS. FORECAST SOUNDINGS SUGGEST THAT VERTICAL SHEAR WILL BE
SUFFICIENTLY STRONG FOR ORGANIZED...SEVERE STORMS INCLUDING BOWS
AND/OR SUPERCELLS. THE PRIMARY SEVERE WEATHER THREAT APPEAR TO BE
DAMAGING WINDS AND LARGE HAIL...THOUGH ISOLATED TORNADOES ARE
POSSIBLE WITH ANY STORMS THAT CAN REMAIN MORE DISCRETE.

STORMS SHOULD QUICKLY MOVE/DEVELOP EWD/NEWD INTO WI AND NRN IL
SUNDAY NIGHT WITH A CONTINUING THREAT OF ISOLATED DAMAGING WINDS AND
SOME HAIL.

.MEAD.. 04/20/2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 200558
SWODY2
SPC AC 200556

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT FRI APR 20 2007

VALID 211200Z - 221200Z

..THERE IS A MDT RISK OF SVR TSTMS SATURDAY AFTERNOON AND EVENING
OVER WRN KS INTO PORTIONS OF THE OK/TX PNHDLS...

..THERE IS A SLGT RISK OF SVR TSTMS FROM WRN TX NWD INTO PORTIONS
OF THE NRN PLAINS...

..SYNOPSIS...

PROGRESSIVE LARGE-SCALE PATTERN WILL EXIST DURING THE DAY TWO PERIOD
WITH THE PRIMARY FEATURE OF INTEREST BEING SHORT WAVE TROUGH WHICH
WILL TRANSLATE EWD FROM THE LOWER CO VALLEY THROUGH THE SRN
ROCKIES...EVENTUALLY EJECTING NEWD AS A NEGATIVELY TILTED TROUGH
INTO THE CNTRL PLAINS BY SUNDAY MORNING.

IN THE LOW-LEVELS...SURFACE LOW INITIALLY OVER WRN NEB WILL DEVELOP
NEWD INTO THE RED RIVER VALLEY OF THE N BY THE END OF THE PERIOD
WHILE SECONDARY CYCLOGENESIS OCCURS SATURDAY OVER NERN CO. COLD
FRONT TRAILING FROM LEAD SURFACE LOW WILL PUSH SEWD FROM THE NRN
HIGH PLAINS THROUGH THE DAKOTAS AND WRN NEB. MEANWHILE...DRYLINE
ATTENDANT TO NERN CO LEE CYCLONE WILL BECOME INCREASINGLY SHARP
THROUGH THE DAY NEAR THE CO-KS BORDER SWD INTO THE WRN OR CNTRL TX
PNHDL AND INTO WRN TX.

..CNTRL/SRN HIGH PLAINS...

POOR LOW-LEVEL TRAJECTORIES ARISING FROM RIDGING OVER THE ERN U.S.
INTO GULF BASIN ARE EXPECTED TO LIMIT THE QUALITY OF BOUNDARY LAYER
MOISTURE WITHIN WARM SECTOR AIR MASS WITH NOTABLE DIFFERENCES
BETWEEN 20/00Z NAM/WRF AND GFS GUIDANCE IN THE EVOLUTION OF THE
MOISTURE/INSTABILITY FIELDS. FORECAST SOUNDINGS ALSO SUGGEST THAT
MID AND HIGH-LEVEL CLOUDINESS MAY TEND TO INCREASE AHEAD OF EJECTING
UPPER TROUGH...WHICH COULD TEMPER DAYTIME HEATING. HOWEVER...IT
DOES APPEAR THAT LOW/MID 50S DEWPOINTS WILL BE SUSTAINABLE WITH
AFTERNOON MIXING...WHICH WHEN COUPLED WITH STEEP MID-LEVEL LAPSE
RATES WILL CONTRIBUTE TO THE DEVELOPMENT OF AN AXIS OF MODERATE
INSTABILITY WITH MLCAPES OF 1000-1500 J/KG.

TSTMS WILL BECOME INCREASINGLY LIKELY BY AFTERNOON FROM PORTIONS OF
WRN/CNTRL NEB SWD THROUGH WRN KS INTO THE TX/OK PNHDLS AND WRN TX AS
INCREASED LARGE-SCALE FORCING FOR ASCENT AHEAD OF UPPER TROUGH AND
DEEPENING DRYLINE CIRCULATION ACT ON DESTABILIZING AIR MASS. SSWLY
50-70 KT MID-LEVEL JET STREAK WILL CONCURRENTLY PROPAGATE EWD ACROSS
WRN EDGE OF INSTABILITY AXIS WITH DEEP LAYER VERTICAL SHEAR BECOMING
INCREASINGLY SUPPORTIVE OF SUPERCELLS. LARGE HAIL /SOME
SIGNIFICANT/ WILL BE THE PRIMARY SEVERE WEATHER THREAT. TORNADOES
WILL ALSO BE POSSIBLE WITH THE MORE INTENSE STORMS GIVEN THE MODEST
LOW-LEVEL SHEAR AND LCL HEIGHTS. THIS SEVERE WEATHER IS EXPECTED TO
BE FAIRLY CONCENTRATED IN A N-S ZONE IMMEDIATELY E OF DRYLINE LATE
SATURDAY AFTERNOON AND EVENING.

SEVERE POTENTIAL SHOULD TEND TO DIMINISH SATURDAY NIGHT AS STORMS
SHIFT E OF INSTABILITY AXIS OVER THE HIGH PLAINS...THOUGH ISOLATED
LARGE HAIL AND/OR LOCALLY DAMAGING WINDS WILL REMAIN POSSIBLE WITH
THE MOST INTENSE CONVECTIVE ELEMENTS.

..NRN PLAINS...

TSTMS /PERHAPS SLIGHTLY ELEVATED/ MAY BE ONGOING SATURDAY MORNING
ALONG LOW-LEVEL FRONTAL ZONE FROM THE RED RIVER VALLEY SWWD INTO WRN
SD...DRIVEN LARGELY BY RATHER STRONG ISENTROPIC ASCENT INVOF OF THIS
BOUNDARY ON NOSE OF LLJ. THESE STORMS MAY PERSIST THROUGH THE DAY
NEAR FRONTAL ZONE DOWNSTREAM FROM DEVELOPING SURFACE LOW WHERE
ISENTROPIC ASCENT AND WAA WILL BE MAINTAINED BY LLJ. OTHER MORE
VIGOROUS SURFACE-BASED STORMS ARE EXPECTED BY AFTERNOON OVER CNTRL
INTO NERN SD ALONG SURFACE LOW TRACK WHERE AIR MASS WILL BECOME
MODERATELY UNSTABLE WITH MLCAPES OF 1000-1500 J/KG.

FORECAST SOUNDINGS SUGGEST THAT VERTICAL SHEAR WILL BE SUPPORTIVE OF
SUPERCELLS CAPABLE OF LARGE HAIL...DAMAGING WINDS AND PERHAPS A
COUPLE OF TORNADOES. OTHER STORMS...MORE LINEAR...WILL LIKELY
DEVELOP ALONG TRAILING COLD FRONT WHERE SEVERE HAIL AND LOCALLY
DAMAGING WINDS WILL BE POSSIBLE.

.MEAD.. 04/20/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 200435
SWODY1
SPC AC 200433

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1133 PM CDT THU APR 19 2007

VALID 201200Z - 211200Z

..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS...

..SYNOPSIS...
HIGHLY AMPLIFIED UPPER AIR PATTERN FCST TO CONTINUE ACROSS CONUS --
DOMINATED BY WRN MEAN TROUGH AND RIDGING FROM WRN GULF TO HUDSON
BAY. MID-UPPER LEVEL LOW INITIALLY OVER ERN MT IS FCST TO EJECT NWD
OVER SASK TOWARD NWRN MB. UPSTREAM LOW -- NOW EVIDENT IN MOISTURE
CHANNEL IMAGERY JUST OFFSHORE NRN CA -- IS FCST TO DIG SEWD OVER SRN
CA/NRN BAJA REGION...THEN PIVOT EWD ACROSS NRN GULF OF CA AND LOWER
CO RIVER VALLEY BY 21/12Z.

AT SFC...DIFFUSE WARM FRONT -- ANALYZED ATTM OVER PORTIONS SRN
MO...ERN KS AND CENTRAL NEB -- IS FCST TO LIFT NWD ACROSS NRN NEB
AND SWRN SD...AND LINK WITH DEVELOPING LEE CYCLONE OVER ERN WY BY
21/00Z. PACIFIC FRONT ASSOCIATED WITH EJECTING MT TROUGH -- AND NOW
ANALYZED FROM CENTRAL NEB TO SWRN KS -- ALSO MARKS WRN EDGE OF
PARTIALLY MODIFIED RETURN FLOW AIR MASS AND ASSOCIATED 50S F SFC DEW
POINTS. THIS BOUNDARY WILL BECOME DIFFUSE AND BACK WWD TOWARD LEE
TROUGH...WITH RESULTING COMBINATION FORMING DRYLINE BETWEEN WRN NEB
AND NRN TX PANHANDLE. DRYLINE ALSO WILL EXTEND SWD ACROSS W TX TO
NRN COAHUILA BY MID/LATE AFTERNOON. NE-SW ALIGNED ZONE OF LOW LEVEL
FRONTOGENESIS ALSO WILL OCCUR FROM SFC LOW OVER ERN ND...ESPECIALLY
AFTER DARK.

SUBTROPICAL/SRN STREAM PERTURBATION IS EVIDENT IN MOISTURE CHANNEL
IMAGERY OVER SRN CHIHUAHUA/DURANGO REGION. DESPITE MISSING UPPER
AIR DATA INPUT FOR NGM/NAM OVER MEX...THIS FEATURE APPEARS TO BE
RESOLVED AND IS REASONABLY PROGGED TO MOVE NEWD ACROSS SWRN/CENTRAL
TX DURING THIS PERIOD. HOWEVER...ANTICYCLONIC FLOW/PRESSURE PATTERN
AT SFC AND ASSOCIATED LACK OF LOW LEVEL FORCING IN PATH OF MID-UPPER
TROUGH SHOULD PRECLUDE SIGNIFICANT CONVECTIVE POTENTIAL.

..CENTRAL/NRN PLAINS...AFTERNOON-EVENING...
ISOLATED TO WIDELY SCATTERED TSTMS ARE POSSIBLE BY LATE AFTERNOON
INVOF DRYLINE FROM WARM FRONTAL INTERSECTION SWD ACROSS WRN KS.
CAPPING BENEATH ROBUST ELEVATED MIXED LAYER SHOULD LIMIT OVERALL
COVERAGE/NUMBER OF TSTMS BY DAY. HOWEVER...ANY ACTIVITY THAT
DEVELOPS IN WARM SECTOR OR ALONG DRYLINE WILL BE IN FAVORABLE
KINEMATIC ENVIRONMENT TO ROTATE -- LARGE/DAMAGING HAIL BEING MAIN
THREAT...AND SVR GUSTS ALSO POSSIBLE. NON-NEGLIGIBLE TORNADO
POTENTIAL EXISTS FOR ANY SFC-BASED TSTMS THAT MAY INTERACT WITH WARM
FRONTAL ZONE OVER WRN/CENTRAL NEB BEFORE DIABATIC SFC COOLING
BECOMES TOO STG TO SUPPORT SFC-BASED EFFECTIVE INFLOW LAYER. SELY
SFC WINDS WILL CONTRIBUTE TO FAVORABLY VEERING WIND PROFILES WITH
HEIGHT AND ENLARGED LOW LEVEL HODOGRAPHS...WITH 0-3 KM SRH ROUGHLY
150-200 J/KG OVER WARM SECTOR PORTION OF CATEGORICAL SLGT RISK
AREA...AND 200-300 J/KG INVOF SFC WARM FRONT.
THERMODYNAMICALLY...MAIN QUESTIONS WILL CONCERN CAPPING AND BOUNDARY
LAYER MOISTURE. FAVORABLE MIDLEVEL LAPSE RATES OF 8-9 DEG C/KM --
OVER 50S F DEW POINTS -- WILL SUPPORT MLCAPES IN 1000-1500 J/KG
RANGE AND LOCALLY HIGHER DURING LATE AFTERNOON SFC THERMAL MAX.

WITH SWD EXTENT ALONG/AHEAD OF DRYLINE...EXPECT GEN INCREASE IN
SBCINH...AS WELL AS GRADUAL WEAKENING OF MIDLEVEL FLOW AND
ASSOCIATED DEEP-LAYER SHEAR. SVR POTENTIAL OVER SWRN KS SWD INTO
NRN TX PANHANDLE THEREFORE BECOMES MUCH MORE CONDITIONAL.

..CENTRAL/NRN PLAINS...AFTER 21/00Z...
CONVECTIVE COVERAGE IS FCST TO INCREASE NEAR AND N OF SFC WARM FRONT
FROM LATE EVENING INTO OVERNIGHT HOURS...SUPPORTED BY MOIST
ADVECTION AND ISENTROPIC ASCENT INVOF 40-50 KT LLJ. WITH EFFECTIVE
SHEAR REMAINING FAVORABLE AS ACTIVITY BUILDS NWD...LARGE HAIL
POTENTIAL LIKEWISE WILL SHIFT NWD OVER NRN NEB AND SD AFTER DARK.
THIS ALSO MAY INCLUDE ADDITIONAL/ELEVATED CONVECTIVE POTENTIAL LATE
IN PERIOD...IN ZONE OF ND FRONTOGENESIS.

.EDWARDS/GRAMS.. 04/20/2007

Thursday, April 19, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 200049
SWODY1
SPC AC 200046

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0746 PM CDT THU APR 19 2007

VALID 200100Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
HIGH AMPLITUDE SYNOPTIC PATTERN WILL CONTINUE OVER CONUS...FEATURING
WRN TROUGH...RIDGING FROM WRN GULF ACROSS GREAT LAKES TO HUDSON
BAY...AND ATLANTIC TROUGHING. STRONG SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY OVER SRN APPALACHIANS...WILL
WEAKEN OVERNIGHT AS IT EJECTS OFFSHORE CAROLINAS. MEANWHILE...UPPER
LEVEL LOW NOW OVER MT/SD BORDER REGION WILL LIFT NWD TO SRN
SASK...AS ANOTHER LOW DIGS SEWD ALONG CA COAST AND TOWARD MEAN
TROUGH POSITION.

AT SFC...DEEP/OCCLUDED LOW INITIALLY ANALYZED OVER E-CENTRAL MT
LIKEWISE WILL LIFT NWD ACROSS CANADIAN BORDER. COLD FRONT TRAILING
SEWD THEN SWD ACROSS NRN/CENTRAL PLAINS WILL WEAKEN...WHILE LEE
TROUGHING CONTINUES TO ITS W AND BENEATH SW FLOW ALOFT. ASSOCIATED
PRESSURE/HEIGHT FALLS SHOULD LEAD TO FRONTAL ZONE AND ACCOMPANYING
MOISTURE GRADIENT BACKING WWD/NWWD OVER WRN KS FROM PRESENT
POSITION. SECONDARY SFC CYCLONE NOW EVIDENT INVOF RTN IS FCST TO
CONSOLIDATE ACROSS NERN NM OVERNIGHT...WITHIN THAT LEE TROUGH. SFC
LOW -- ASSOCIATED WITH SRN APPALACHIANS PERTURBATION ALOFT -- WAS
ANALYZED AT 00Z OVER CENTRAL SC...AND SHOULD MOVE SEWD TOWARD COAST
ALONG QUASISTATIONARY FRONTAL ZONE.

..SC...
SCATTERED TSTMS -- MANY OF THEM BECOMING ELEVATED JUST ABOVE
DIABATICALLY STABILIZING NEAR-SFC LAYER -- WILL CONTINUE TO MOVE
GENERALLY SEWD THROUGH REMAINDER EVENING. MOST INTENSE TSTMS MAY
PRODUCE HAIL. THOUGH NOT PARTICULARLY STG...PRESENCE OF RELATIVELY
BACKED LOW LEVEL WINDS E OF SFC LOW IS EXPECTED TO ENHANCE
STORM-RELATIVE INFLOW AND BULK SHEAR...WHICH APPEAR FAVORABLE FOR
MAINTAINING SOME SVR PROBABILITIES BASED ON RUC FCST
SOUNDINGS...PRE-STORM CAE VWP...AND MODIFIED CHS RAOB DATA. REF SPC
MESOSCALE DISCUSSING 517 FOR ADDITIONAL/NOWCAST DETAILS.

..CENTRAL PLAINS....
POTENTIAL REMAINS ATTM FOR ISOLATED TO WIDELY SCATTERED TSTM
DEVELOPMENT INVOF WEAKENING COLD FRONT OVER PORTIONS S-CENTRAL NEB
SWWD TOWARD W-CENTRAL/SWRN KS. HOWEVER...DIABATIC COOLING OF
NEAR-SFC LAYER DURING NEXT FEW HOURS WILL LEAD TO INCREASINGLY
ELEVATED EFFECTIVE INFLOW PARCELS AND REDUCTION IN SVR GUST
POTENTIAL WITH ANY SUCH ACTIVITY. CONDITIONAL HAIL POTENTIAL WILL
REMAIN GIVEN SUSTAINED STORM DEVELOPMENT...WITH DEEP-LAYER/EFFECTIVE
SHEAR BEING FAVORABLE AT 40-45 KT AND MUCAPES 500-1000 J/KG.

..NRN PLAINS...
HEIGHT RISES ARE FCST ACROSS MUCH OF THIS REGION FOR REMAINDER
PERIOD...IN WAKE OF EJECTING MID/UPPER CYCLONE. WITH PRESENCE OF
FRONTOLYSIS...LITTLE OR NO SUPPORT FROM MID/UPPER LEVEL
FORCING...AND DECREASING SFC HEATING...OVERALL POTENTIAL FOR
CONVECTION AND ESPECIALLY SVR POTENTIAL WILL WEAKEN THROUGH
REMAINDER EVENING/OVERNIGHT HOURS.

.EDWARDS.. 04/20/2007

MESO: Mesoscale Discussion 0517

ACUS11 KWNS 200016
SWOMCD
SPC MCD 200016
SCZ000-200145-

MESOSCALE DISCUSSION 0517
NWS STORM PREDICTION CENTER NORMAN OK
0716 PM CDT THU APR 19 2007

AREAS AFFECTED...PARTS OF CENTRAL AND ERN SC

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 200016Z - 200145Z

ISOLATED SEVERE STORMS REMAIN POSSIBLE FOR AT LEAST THE NEXT
HOUR...MAINLY NEAR AND N THROUGH E OF CAE...WITH ACTIVITY EXPECTED
TO DIMINISH IN INTENSITY AFTER 01-02Z.

REGIONAL RADARS INDICATED A CLUSTER OF TSTMS EXTENDING FROM CAE TO
50 NE OF CAE AND TRACKING SEWD AT 20-25 KT. ALTHOUGH INSTABILITY
REMAINS WEAK...STRONG FORCING ALONG LEADING EDGE OF COMPACT MID
LEVEL IMPULSE AND 35-40 KT OF EFFECTIVE BULK SHEAR HAVE SUPPORTED A
FEW ORGANIZED SEVERE STORMS THUS FAR. MEANWHILE...SEA BREEZE
CONTINUES TO MOVE WELL INLAND AND EXTENDED FROM 20 E VDI TO 25 ESE
AGS TO 35 E CAE TO 40 S FAY. TSTMS NEAR AND NE OF CAE ARE EXPECTED
TO DECREASE IN INTENSITY AS THEY ENCOUNTER A MORE STABLE AIR MASS TO
THE E OF THE SEA BREEZE...AND ALSO AS THE BOUNDARY LAYER STABILIZES
WITH LOSS OF DAYTIME HEATING.

A FEW ADDITIONAL TSTMS WILL BE POSSIBLE AS ISENTROPIC ASCENT ATOP
MORE STABLE AIR MASS TO THE E OF SEA BREEZE AND ASCENT WITH MID
LEVEL IMPULSE SUPPORTS TSTM DEVELOPMENT. COLD MID LEVEL
TEMPERATURES WILL PROMOTE AN ADDITIONAL HAIL THREAT WITH THE
STRONGER STORMS THIS EVENING.

.PETERS.. 04/20/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ILM...CHS...CAE...

33238057 33638103 34018112 34178085 34338038 34157979
33787935 33277958 33038004

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191949
SWODY1
SPC AC 191947

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT THU APR 19 2007

VALID 192000Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SRN APPALACHIANS TO SC COAST...

CONVECTION IS SLOWLY DEEPENING ACROSS THE SRN APPALACHIANS WITHIN
EXIT REGION OF UPPER SPEED MAX. THIS FEATURE IS EXPECTED TO SHIFT
SEWD...ALONG WITH FOCUSED ZONE OF ASCENT...WHICH SHOULD AID
ADDITIONAL THUNDERSTORMS ALONG ERN EDGE OF STRONGER BOUNDARY LAYER
HEATING. GA IN PARTICULAR HAS WARMED SIGNIFICANTLY THIS AFTERNOON
WITHIN WEAK WLY FLOW REGIME WHERE TEMPERATURES HAVE WARMED INTO THE
70S. ADDITIONALLY...ANY STORMS THAT DEVELOP SEWD ACROSS SC SHOULD
WITH TIME INTERACT WITH SEA BREEZE POSSIBLY ENHANCING UPDRAFTS AT
THAT TIME. MARGINALLY SEVERE HAIL OR PERHAPS GUSTY WINDS ARE THE
MAIN THREAT.

..NRN/CNTRL PLAINS...

WELL DEFINED UPPER VORT IS LIFTING NEWD ACROSS THE BLACK HILLS
REGION OF WY/SD THIS AFTERNOON. ALTHOUGH CU FIELD IS EXPANDING
WITHIN THE CLEAR SLOT...INVOF THIS CIRCULATION...A VERY NARROW ZONE
OF PRE-FRONTAL DESTABILIZATION IS EXPECTED DOWNSTREAM ACROSS CNTRL
SD. MODELS CONTINUE TO INSIST THAT A FEW STORMS MAY EVOLVE ALONG
LEADING EDGE OF NEWD-EXPANDING CU FIELD NEAR THE MAIN WIND SHIFT.
GIVEN THE SHEAR PROFILES IT REMAINS POSSIBLE FOR A FEW ORGANIZED
UPDRAFTS CAPABLE OF PRODUCING GUSTY WINDS OR PERHAPS SOME HAIL.

FARTHER SOUTH...BOUNDARY LAYER MOISTENING IS GRADUALLY UNDERWAY
ACROSS THE SRN PLAINS INTO KS...WHERE SFC DEW POINTS ARE NOW RISING
INTO THE 50S AS FAR NORTH AS I-70. LATEST SATELLITE IMAGERY DEPICTS
THIS BOUNDARY LAYER RECOVERY QUITE WELL WITH BOUNDARY LAYER CU
DEVELOPING ACROSS WRN OK...AND EXPANDING ACROSS MUCH OF WRN/CNTRL
KS. LARGE SCALE IS NOT PARTICULARLY FAVORABLE ACROSS THIS REGION
WITH RIDGY CIRRUS NOW SPREADING ACROSS TX PANHANDLE/OK. IT REMAINS
TO BE SEEN WHETHER CONVERGENCE FARTHER NORTH OVER KS WILL PROVE
ADEQUATE IN INITIATING...THEN MAINTAINING THUNDERSTORMS. IF SO...A
FEW UPDRAFTS COULD PRODUCE SOME HAIL OR GUSTY WINDS.

.DARROW.. 04/19/2007

MESO: Mesoscale Discussion 0516

ACUS11 KWNS 191708
SWOMCD
SPC MCD 191708
SCZ000-NCZ000-GAZ000-VAZ000-TNZ000-191945-

MESOSCALE DISCUSSION 0516
NWS STORM PREDICTION CENTER NORMAN OK
1208 PM CDT THU APR 19 2007

AREAS AFFECTED...WRN NC INTO SC

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 191708Z - 191945Z

TSTMS WILL INCREASE FROM THE TN/NC/VA APPALACHIANS SEWD INTO THE SC
COASTAL PLAIN THIS AFTN/EVE. SEVERE HAIL AND DAMAGING WINDS WILL BE
PSBL IN ISOLD STRONGER STORMS.

H5 LOW /AOB MINUS 20 DEG C/ WAS LOCATED OVER THE KY COALFIELDS EARLY
THIS AFTN...ROTATING ALONG WRN PERIPHERY OF A LARGER SCALE SYSTEM
OVER THE N ATLANTIC BASIN. THE KY IMPULSE WILL CONTINUE TO ROTATE
SEWD INTO THE SERN STATES THROUGH THE EVE. LATEST SFC ANALYSIS
PLACES A NW-SE ORIENTED FRONT FROM JUST W OF KAVL-KCAE- KCHS. THE
FRONT HAS BECOME DIFFUSE WITH WINDS VEERING AND STRATUS DISSOLVING
IN THE COLDER AIR. AS A RESULT...TEMPERATURES SHOULD RISE WELL INTO
THE 70S IN THE SAVANNAH RVR VLY AND INTO THE UPPER 60S ACROSS
UPSTATE...NCNTRL AND COASTAL SC. BOUNDARY LAYER MOISTURE WAS
SOMEWHAT MARGINAL...WITH SFC DEW POINTS ON THE ORDER OF 45-55 DEG F.
BUT...STEEPENING LAPSE RATES ALOFT ASSOCD WITH THE MID-LEVEL
DISTURBANCE WILL SPREAD SEWD DURING THE AFTN AND CONTRIBUTE TO A
BUOYANT AIR MASS.

TSTMS DEVELOPING ALONG THE HIGHER TERRAIN OF VA/TN/NC SHOULD
EXPAND/DEVELOP SEWD ACROSS MUCH OF WRN NC AND SC DURING THE MID-LATE
AFTN/EVE. STRONGER STORMS ARE EXPECTED TO FAVOR THE WEAK FRONT
WHERE SLIGHTLY STRONGER MASS CONVERGENCE SHOULD EXIST. WIND
PROFILES WILL BE SUPPORTIVE OF SUPERCELLS...BUT MEAGER MOISTURE WILL
TEND TO LIMIT ORGANIZATION. PRIMARY MODE WILL BE LOW-TOPPED
MULTICELL STRUCTURES...POSSIBLY EVOLVING INTO SHORT LINE SEGMENTS.
COLD AIR ALOFT WILL FOSTER HAIL PRODUCTION AND RELATIVELY DRY
SUB-CLOUD LAYER MAY YIELD DAMAGING WIND GUSTS WITH ANY BOWING
SEGMENTS. ATTM...EXPECT THE CURRENT THREAT TO REMAIN ISOLD...BUT
WILL MONITOR FOR A PSBL WW LATER THIS AFTN.

.RACY.. 04/19/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ILM...RNK...CHS...CAE...GSP...MRX...FFC...

32408075 34828391 36638230 35218072 33297945

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 191706
SWODY2
SPC AC 191705

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1205 PM CDT THU APR 19 2007

VALID 201200Z - 211200Z

..NO SVR TSTM AREAS FORECAST...

..PLAINS...

UPPER RIDGE WILL GRADUALLY SHIFT EAST INTO THE MS VALLEY LATE DAY2
AS UPPER TROUGH SETTLES INTO THE GREAT BASIN/SWRN U.S. AHEAD OF
THIS FEATURE WEAK HEIGHT RISES WILL AFFECT MUCH OF THE PLAINS
THROUGH THE AFTERNOON HOURS...THUS LOW LEVEL WARM ADVECTION WILL
LIKELY PROVE THE MAIN INSTIGATOR IN CONVECTIVE DEVELOPMENT MUCH OF
THE PERIOD.

ONE CLEAR SIGNAL IN 12Z MODEL GUIDANCE IS THE EXPECTED INCREASE IN
LLJ ACROSS THE PLAINS...ESPECIALLY ACROSS THE CNTRL PLAINS DURING
THE LATTER HALF OF THE PERIOD WHERE SPEEDS SHOULD EXCEED 40-50 KT.
UNDOUBTEDLY ANY MOISTENING ACROSS THIS REGION WILL LIKELY LEAD TO
ELEVATED CONVECTION AT TIMES...LIKELY DEVELOPING OVER KS DURING THE
DAY1 PERIOD...SHIFTING/SPREADING NWD INTO THE ERN DAKOTAS DURING THE
OVERNIGHT HOURS FRIDAY.

OF PARTICULAR CONCERN IS THE STRENGTHENING CAP ACROSS THIS REGION
AND THE POSSIBILITY FOR SUFFICIENT HEATING/CONVERGENCE ALONG THE DRY
LINE FOR DEEP CONVECTION LATE AFTERNOON. GIVEN THE UPSTREAM TROUGH
POSITION...IT APPEARS THE DRY LINE WILL SET UP ACROSS THE HIGH
PLAINS FROM THE TX/NM BORDER...NWD INTO ERN CO/NEB PANHANDLE. THIS
ZONE WILL CERTAINLY RECEIVE STRONG HEATING...LIKELY ENOUGH FOR CAP
REMOVAL. WEAK LARGE SCALE RIDGING AND MEAGER LOW LEVEL CONVERGENCE
HOWEVER WILL PROVE DETRIMENTAL IN ORGANIZED DEEP CONVECTION. AT
THIS TIME IT APPEARS ONLY ISOLATED THUNDERSTORMS...A FEW OF WHICH
COULD ATTAIN SUPERCELL CHARACTERISTICS...SHOULD BE NOTED ALONG THE
DRY LINE FROM WEST TX...NWD INTO WRN NEB. LIMITED COVERAGE WILL NOT
WARRANT A SLIGHT RISK ACROSS THIS REGION.

.DARROW.. 04/19/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191643
SWODY1
SPC AC 191640

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1140 AM CDT THU APR 19 2007

VALID 191630Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SOUTHERN APPALACHIANS AND CAROLINAS THROUGH EARLY EVENING...
COMPACT MID LEVEL LOW CONTINUES TO PIVOT SOUTHEASTWARD OVER EASTERN
KY AT MIDDAY PER WATER VAPOR IMAGERY...WITH THIS FEATURE EXPECTED TO
REACH THE SC COAST LATE TONIGHT. IN ADDITION TO THE PARENT UPPER
LOW...A WEAK NW-SE ORIENTED BOUNDARY WILL PROVIDE A FOCUS FOR
THUNDERSTORM DEVELOPMENT...WITH STORMS EXPECTED TO DEVELOP
SOUTHEASTWARD THROUGH WESTERN NC AND THE SC PIEDMONT/COASTAL PLAIN
THROUGH EARLY EVENING. IN ADDITION TO GUSTY WIND POTENTIAL...COLD
MID LEVEL TEMPERATURES /-23 C AT 500 MB PER 12Z WILMINGTON OH
OBSERVED RAOB/ AND ASSOCIATED STEEP LAPSE RATE ENVIRONMENT WILL
FAVOR HAIL POTENTIAL WITH SEMI-ORGANIZED MULTICELL/MARGINAL
SUPERCELL STORMS THROUGH EARLY EVENING.

..PORTIONS OF SD/NEB/KS THIS AFTERNOON AND TONIGHT...
WATER VAPOR IMAGERY FEATURES UPPER TROUGH SHIFTING NORTHWARD ACROSS
WY AND FAR SOUTHERN MT AT MIDDAY...WITH A PACIFIC/OCCLUDED FRONT
ADVANCING EASTWARD INTO THE WESTERN DAKOTAS/WESTERN NEB. BOUNDARY
LAYER MOISTURE ONLY IN THE 40S F AND EXISTING CLOUD COVER WILL
CONSIDERABLY LIMIT POTENTIAL INSTABILITY THROUGH THE AFTERNOON
ACROSS MUCH OF SD/NEB...HOWEVER AN ISOLATED HAIL PRODUCING STORM
CANNOT BE RULED OUT. ALTHOUGH CONDITIONAL...A RELATIVELY GREATER
SEVERE THREAT EXISTS LATE THIS AFTERNOON/EVENING WITH SOUTH EXTENT
ALONG THE SLOW EASTWARD MOVING FRONTAL BOUNDARY INTO CENTRAL
PORTIONS OF KS. EVEN WITH RISING UPPER HEIGHTS/ONSET OF UPPER
RIDGING...12Z DETERMINISTIC NAM/GFS AND 09Z SREF GUIDANCE SUGGEST
ISOLATED STORMS ARE PLAUSIBLE BY EARLY EVENING INTO CENTRAL
KS...WITH THE POSSIBILITY OF A FEW SUPERCELLS CAPABLE OF LARGE HAIL
AND GUSTY WINDS.

.GUYER/HART.. 04/19/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191232
SWODY1
SPC AC 191230

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0730 AM CDT THU APR 19 2007

VALID 191300Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
A COMPLEX FLOW REGIME WILL PERSIST OVER THE CONUS WITH A BROAD
TROUGH OVER THE WRN STATES...A RIDGE FROM THE SRN PLAINS TO THE
GREAT LAKES...AND ANOTHER TROUGH OVER THE WRN ATLANTIC AND ERN
SEABOARD. WITHIN THIS BROADER FLOW REGIME...ONE SHORTWAVE TROUGH
WILL EJECT NNEWD FROM CO/WY THIS MORNING TO ERN MT/WRN ND BY TONIGHT
AS ANOTHER STRONG TROUGH APPROACHES CA FROM THE ERN PAC. FARTHER
E...A COMPACT MID LEVEL LOW OVER THE LOWER OH VALLEY WILL MOVE SEWD
OVER THE SAVANNAH RIVER VALLEY BY THIS EVENING. THE PRIMARY
THUNDERSTORM THREAT AREAS WILL BE FOCUSED ALONG THE PATHS OF THE NRN
PLAINS AND SERN STATES SHORTWAVE TROUGHS AND ASSOCIATED SURFACE
REFLECTIONS.

..CENTRAL AND NRN PLAINS TODAY INTO TONIGHT...
A STRONG MID LEVEL SHORTWAVE TROUGH IS EJECTING NNEWD AROUND THE WRN
PERIPHERY OF THE BLOCKING RIDGE FROM ONTARIO SSWWD INTO THE SRN
PLAINS. A DEEP SURFACE CYCLONE WILL DEVELOP GENERALLY NWD ALONG A
BAROCLINIC ZONE ACROSS ERN MT...WHILE A WEAKENING PACIFIC COLD FRONT
SWEEPS EWD TODAY ACROSS NEB/SD.

A WNW-ESE ORIENTED BAND OF CLOUDS/RAIN WILL SPREAD NEWD ACROSS THE
DAKOTAS/MT TODAY IN THE REGION OF STRONG ASCENT DOWNSTREAM FROM THE
MID LEVEL TROUGH...THOUGH FORCING FOR ASCENT SHOULD WEAKEN GRADUALLY
AS THE ENTIRE SYSTEM BEGINS TO LOSE AMPLITUDE. INSTABILITY WILL BE
QUITE LIMITED WITHIN THE INITIAL PRECIPITATION BAND GIVEN THE RATHER
POOR LAPSE RATES AND LIMITED LOW-LEVEL MOISTURE ACROSS THE NRN
PLAINS. HOWEVER...THERE WILL BE SOME THREAT FOR ADDITIONAL STORM
DEVELOPMENT THIS AFTERNOON IN SD WITH THE MID LEVEL THERMAL TROUGH
AND STEEPER LOW-MID LEVEL LAPSE RATES.

SOMEWHAT GREATER MOISTURE /BOUNDARY LAYER DEWPOINTS IN THE LOW-MID
50S/ WILL SPREAD NWD ACROSS KS TO SRN NEB BY LATE AFTERNOON IN
ADVANCE OF THE SURFACE BOUNDARY SAGGING SEWD. THIS BOUNDARY SHOULD
STALL BY EARLY TONIGHT...AND PERHAPS BEGIN TO LIFT NWWD AS A WARM
FRONT ACROSS WRN KS AND CENTRAL NEB TOWARD MORNING. THE INCREASING
MOISTURE AND AFTERNOON TEMPERATURES NEAR 70 F WILL CONTRIBUTE TO
MLCAPE VALUES NEAR 500 J/KG ALONG THE BOUNDARY IN KS...WHERE COOLING
IN THE 850-700 MB LAYER AND REDUCED CONVECTIVE INHIBITION COULD
ALLOW ONE OR TWO THUNDERSTORMS TO DEVELOP BY LATE AFTERNOON. IF
STORMS FORM...THE WEAK INSTABILITY AND MODEST DEEP LAYER SHEAR MAY
SUPPORT SPLITTING/SUPERCELL STORMS WITH A MARGINAL HAIL/WIND THREAT.
BY TONIGHT...THE POSSIBILITY WILL ALSO EXIST FOR ELEVATED STORMS IN
A WEAK WAA REGIME ALONG AND JUST NW OF THE RETREATING SURFACE
BOUNDARY IN KS...WHERE THE THREAT FOR SOME HAIL COULD PERSIST
OVERNIGHT.

..SRN APPALACHIANS/SC AREA FROM MIDDAY INTO EARLY TONIGHT...
A CONCENTRATED REGION OF ASCENT WILL ACCOMPANY THE COMPACT MID LEVEL
LOW ACROSS THE SRN APPALACHIANS AND SC TODAY INTO THIS EVENING. A
WEAK SURFACE LOW IS EXPECTED TO DEVELOP SEWD ALONG A PRE-EXISTING
BOUNDARY /ROUGHLY ALONG THE SAVANNAH RIVER/...AND THE AREA NEAR AND
IMMEDIATELY SE OF THE SURFACE LOW SHOULD BE THE FOCUS FOR
THUNDERSTORM DEVELOPMENT TODAY. DESPITE THE PRIOR PASSAGE OF A
WEAKENING SRN STREAM TROUGH AND ASSOCIATED COLD FRONTAL PASSAGE...A
NARROW CORRIDOR OF 48-52 F DEWPOINTS SHOULD PERSIST ALONG AND JUST E
OF THE SECONDARY BOUNDARY ALONG THE SC/GA BORDER. THIS RESIDUAL
MOISTURE...ALONG WITH SOME DAYTIME HEATING AND STEEPER LAPSE RATES
WITH THE SMALL COLD CORE LOW...WILL RESULT IN AFTERNOON MLCAPE
VALUES OF 200-400 J/KG. RELATIVELY COOL MID LEVEL TEMPERATURES AND
EFFECTIVE BULK SHEAR OF 30-35 KT COULD SUPPORT A FEW
ORGANIZED/MARGINAL SUPERCELL STORMS CAPABLE OF PRODUCING SOME HAIL
AND STRONG OUTFLOW GUSTS THIS AFTERNOON INTO EARLY TONIGHT.

.THOMPSON/GRAMS.. 04/19/2007

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 190856
SWOD48
SPC AC 190856

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0356 AM CDT THU APR 19 2007

VALID 221200Z - 271200Z

..DISCUSSION...
IT APPEARS ATTM THAT SEVERE WEATHER THREAT SHOULD BE RELATIVELY
LIMITED ACROSS THE MID AND UPPER MS VALLEY/WRN UPPER GREAT LAKES
REGION DAY 4 /SUN. APR. 22/ AS UPPER SYSTEM CONTRIBUTING TO THE
SEVERE WEATHER THREAT IN THE PLAINS DAY 3 LIFTS NEWD ACROSS A LESS
THERMODYNAMICALLY-FAVORABLE ENVIRONMENT.

BOTH THE GFS AND THE ECMWF SHOW ANOTHER SIGNIFICANT UPPER TROUGH/LOW
TO TRAVERSE THE ROCKIES INTO EARLY NEXT WEEK...WHICH IT APPEARS
SHOULD EMERGE INTO THE PLAINS AROUND DAY 6 /TUE. APR. 24/.
HOWEVER...LOCATION OF THIS FEATURE -- AND ASSOCIATED SURFACE
CYCLOGENESIS ARE DEPICTED DRASTICALLY DIFFERENT IN THE TWO MODELS.
AS A RESULT...DEGREE OF UNCERTAINTY PRECLUDES THE ISSUANCE OF A
SEVERE WEATHER AREA ATTM.

.GOSS.. 04/19/2007

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 190737
SWODY3
SPC AC 190735

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0235 AM CDT THU APR 19 2007

VALID 211200Z - 221200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN PLAINS SSWWD INTO
THE SRN HIGH PLAINS...

..SYNOPSIS...
MODELS CONTINUE TO DEPICT THE LARGE WRN U.S. TROUGH CROSSING THE
ROCKIES AND REACHING THE PLAINS THIS PERIOD...THOUGH MODELS ARE AT
LEAST 6 HOURS SLOWER WITH THE EWD-PROGRESSION OF THIS FEATURE THAN
PRIOR RUNS.

AT THE SURFACE...PRESSURE FALLS WILL CONTINUE IN THE LEE OF THE
ROCKIES...WITH THE LOW/TROUGH PROGRESSING EWD OFF THE HIGH PLAINS
THROUGH THE END OF THE PERIOD.

..SRN HIGH PLAINS NNEWD INTO THE DAKOTAS/WRN MN...
QUESTIONS EXIST THIS PERIOD REGARDING DEGREE OF MOISTURE
RETURN...BUT EXPECT GENERALLY 50S DEWPOINTS TO ADVECT NWWD INTO THE
PLAINS. THIS SHOULD BE SUFFICIENT FOR THE DEVELOPMENT OF 500 TO
1000 J/KG MEAN-LAYER CAPE OVER THE HIGH PLAINS AND INTO NEB/SD.
HOWEVER...MODEST MOISTURE COMBINED WITH THE SLOWER MOVEMENT OF THE
UPPER TROUGH -- AND THUS STRONGER SUBSIDENCE/CAPPING BENEATH THE
UPPER RIDGE OVER MOST OF TX/OK/CENTRAL AND ERN KS -- SUGGESTS THAT
THE PRIMARY SEVERE THREAT SHOULD REMAIN CONFINED TO THE HIGH PLAINS.

FURTHER N...LOCATION AND DEGREE OF SEVERE THREAT WILL DEPEND UPON
INTENSITY OF THE LOW EVOLVING OVER THE CENTRAL HIGH PLAINS -- AND
THE RESULTING LOCATION OF THE NEWD-EXTENDING TROUGH/WARM FRONT.

ATTM...IT APPEARS THAT STRONG DEEP-LAYER SHEAR AND DEWPOINTS
GENERALLY IN THE MID 50S SHOULD SUPPORT THE DEVELOPMENT OF SUPERCELL
STORMS FROM THE CENTRAL AND SRN HIGH PLAINS NNEWD ACROSS THE WRN
HALF OF NEB AND INTO THE DAKOTAS AND PERHAPS WRN MN. GREATEST
THREAT WILL LIKELY EXIST FROM THE TX/OK PANHANDLES NWD ACROSS WRN
KS/ERN CO INTO THE WRN HALF OF NEB. IN THESE AREAS...LARGE HAIL AND
DAMAGING WINDS WILL BE POSSIBLE ALONG WITH ISOLATED TORNADOES.

THOUGH STORMS -- AND SOME SEVERE THREAT -- WILL SHIFT SLOWLY EWD
OVERNIGHT -- AND POSSIBLY TAKING ON A MORE LINEAR
ORGANIZATION...OVERALL EWD EXTENT OF THE THREAT WILL LIKELY BE
LIMITED DUE TO MODEST BOUNDARY-LAYER MOISTURE/OVERALL INSTABILITY.

.GOSS.. 04/19/2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 190600
SWODY2
SPC AC 190559

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT THU APR 19 2007

VALID 201200Z - 211200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
LARGE RIDGE IS FORECAST TO PREVAIL OVER THE CENTRAL CONUS THIS
PERIOD...DOWNSTREAM OF STRONG TROUGH MOVING SLOWLY EWD ACROSS THE
WRN CONUS. THE APPROACH OF THIS SYSTEM WILL HELP INDUCE PRESSURE
FALLS IN LEE OF THE ROCKIES...AND THUS A SLY FLOW/WARM ADVECTION
REGIME OVER THE PLAINS.

SCATTERED STORMS WILL BE POSSIBLE ACROSS PARTS OF THE WRN U.S.
WITHIN LARGE-SCALE CYCLONIC FLOW/TROUGHING...AND A PRIMARILY
NOCTURNAL CONVECTIVE EVENT WILL ALSO BE POSSIBLE OVER THE
CENTRAL/NRN PLAINS. ELSEWHERE...APPRECIABLE DEEP/MOIST CONVECTION
IS NOT ANTICIPATED.

..NRN PLAINS SWD INTO THE SRN HIGH PLAINS...
MODELS ARE TRENDING SLOWER WITH THE PROGRESSION OF THIS
FEATURE...WHICH IS RESULTING IN THE LIKELIHOOD OF LESS RETURN FLOW
INTO THE PLAINS AS WELL AS STRONGER SUBSIDENCE/CAPPING.
THUS...CONFIDENCE REMAINS LOW THAT STORM DEVELOPMENT WILL OCCUR
ALONG THE SRN HIGH PLAINS DRYLINE.

STORM POTENTIAL APPEARS TO INCREASE WITH NWD EXTENT -- PARTICULARLY
INTO THE OVERNIGHT HOURS...AS LOW-LEVEL JET INCREASES. THIS WILL
LIKELY SUPPORT FAIRLY WIDESPREAD STORMS FROM KS/NEB NWD INTO THE
DAKOTAS.

SHEAR SHOULD REMAIN SOMEWHAT LIMITED ACROSS MUCH OF THE
PLAINS...WITH LARGE RIDGE IN PLACE. THIS COMBINED WITH LIMITED
INSTABILITY SUGGESTS CONVECTION WILL REMAIN LARGELY NON-SEVERE.
GREATEST SEVERE POTENTIAL WILL LIKELY EXIST FROM LATE AFTERNOON
THROUGH MID-EVENING FROM ACROSS PARTS OF KS AND NEB...WHERE MOST
FAVORABLE JUXTAPOSITION OF CAPE AND SHEAR SHOULD EXIST.
HOWEVER...THREAT APPEARS ATTM TO REMAIN SUFFICIENTLY LIMITED SUCH
THAT A SLIGHT RISK WILL NOT BE INTRODUCED THIS FORECAST.

.GOSS.. 04/19/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 190533
SWODY1
SPC AC 190531

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 AM CDT THU APR 19 2007

VALID 191200Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
HIGH-AMPLITUDE SYNOPTIC PATTERN WILL CONTINUE OVER CONUS THROUGH
PERIOD. SOME EWD SHIFT OF WRN TROUGH/CENTRAL RIDGE/ERN TROUGH
PATTERN IS FCST BY 20/12Z...AS HEIGHTS RISE IN WAKE OF STRONG
SHORTWAVE TROUGH AND ACCOMPANYING UPPER LOW NOW OVER INDIANA. THIS
PERTURBATION SHOULD DIG SEWD ACROSS SRN APPALACHIANS DURING
DAY...THEN ACCELERATE ESEWD ACROSS CAROLINAS AND DEAMPLIFY AFTER
20/00Z. ASSOCIATED SFC CYCLONE -- ANALYZED ATTM OVER CENTRAL
APPALACHIANS -- ALSO WILL MOVE SEWD ACROSS SAV RIVER REGION OR SRN
SC.

FARTHER NW...STRONG MID/UPPER LEVEL LOW -- NOW EVIDENT IN MOISTURE
CHANNEL IMAGERY OVER SRN ID -- IS EXPECTED TO LIFT NEWD ACROSS
WRN/NRN WY AND ERN MT...BECOMING MORE CLOSELY STACKED IN VERTICAL
WITH SFC CYCLONE. ASSOCIATED LOW LEVEL FRONT WILL CONTINUE TO SWEEP
EWD OVER CENTRAL ROCKIES AND NRN HIGH PLAINS...REACHING WRN PORTIONS
SD/NEB/KS BY 20/00Z AND OCCLUDING WITH WARM FRONT OVER SWRN SD OR
N-CENTRAL/NWRN NEB. WARM FRONT SHOULD LIFT NWD SLOWLY ACROSS ERN
PORTIONS NEB/KS AND CENTRAL SD...AS STRONG ISALLOBARIC FORCING
MAINTAINS STRONG ELY FLOW COMPONENT TO ITS NE. COLD FRONT ALSO WILL
ACT AS EFFECTIVE DRYLINE...FOLLOWED BY DRY/WLY DOWNSLOPE FLOW ACROSS
CENTRAL HIGH PLAINS.

..SERN CONUS...
WIDELY SCATTERED TO SCATTERED TSTMS SHOULD MOVE/DEVELOP SEWD ACROSS
NARROW SWATH AHEAD OF SFC LOW...MOST VIGOROUS OF WHICH MAY PRODUCE
HAIL. GUSTS SHOULD REMAIN GENERALLY BELOW 50 KT SVR CRITERIA BUT
STILL MAY HARM SOME TREES AND PRODUCE MINOR DAMAGE TO CONSTRUCTION.
MAIN LIMITING FACTOR WILL BE LACK OF MORE ROBUST MOISTURE...WITH DEW
POINTS REMAINING BELOW 60 F MOST AREAS. NONETHELESS...COLD MIDLEVEL
TEMPS...SFC DIURNAL HEATING...AND WEAK CINH SHOULD CONTRIBUTE TO
NARROW PLUME OF MRGL SFC-BASED BUOYANCY -- BELOW 500 J/KG -- IN
ADVANCE OF SFC LOW TRACK. THIS SHOULD BE SUFFICIENT TO SUPPORT
CLUSTER OF TSTMS MOVING SEWD FROM HIGHER TERRAIN THROUGH AFTERNOON
HOURS...ACROSS PIEDMONT AND PERHAPS ONTO COASTAL PLAIN BY EARLY
EVENING. ALTHOUGH LOW LEVEL FLOW IS NOT FCST TO BE PARTICULARLY STG
INVOF SFC LOW...BACKED FLOW TO ITS E WILL ENHANCE BOTH
STORM-RELATIVE INFLOW AND DEEP-LAYER BULK SHEAR. NEARLY STRAIGHT
LINE HODOGRAPHS ALSO MAY SUPPORT SOME STORM SPLITTING AND BRIEF
SUPERCELL STRUCTURES.

..CENTRAL/NRN PLAINS...
TSTMS MAY BE ONGOING AT BEGINNING OF PERIOD OVER PORTIONS
CENTRAL/NRN HIGH PLAINS -- CARRYING OVER FROM ONGOING ACTIVITY NOW
OVER PORTIONS WY/MT. ADDITIONAL DEVELOPMENT WITH STG GUSTS AND/OR
HAIL IS POSSIBLE BY MID/LATE AFTERNOON OVER WRN/CENTRAL
DAKOTAS...AND BEHIND RESIDUAL CLOUD/PRECIP DEBRIS...BUT WITH VERY
LIMITED LOW LEVEL THERMODYNAMIC SUPPORT. LACK OF RICHER MOISTURE
WILL KEEP MLCAPES BELOW 500 J/KG IN MOST AREAS...DESPITE STEEP
MIDLEVEL LAPSE RATES. ALTHOUGH SFC DEW POINTS AND DIURNAL HEATING
EACH WILL BE STRONGER WITH SWD EXTENT ALONG/AHEAD OF
FRONT/DRYLINE...STRONGEST MID/UPPER ASCENT WILL PASS N OF NEB/KS BY
LATE AFTERNOON AND THIS AREA WILL LIE BEHIND AXIS OF TROUGH ALOFT.
SFC HEATING AND FRONTAL ASCENT MAY BE VIGOROUS ENOUGH TO INITIATE
BKN LINE OF CONVECTION DURING LATE AFTERNOON FROM S-CENTRAL/SERN NEB
TO N-CENTRAL/W-CENTRAL KS. STRONGEST STORMS MAY PRODUCE GUSTS AND
HAIL NEAR SVR LEVELS. CONVECTION SHOULD DIMINISH MARKEDLY AFTER
DARK.

.EDWARDS/GRAMS.. 04/19/2007

Wednesday, April 18, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 190100
SWODY1
SPC AC 190058

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT WED APR 18 2007

VALID 190100Z - 191200Z

..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NERN WY...ERN MT...

..SYNOPSIS...
HIGHLY AMPLIFIED UPPER AIR PATTERN EXISTS ACROSS
CONUS...CHARACTERIZED PRIMARILY BY UPPER LOW CENTERED OVER SRN
ID...RIDGING FROM NWRN ONT HIGH SSWWD TO LOWER TX COAST...AND NEARLY
ZONALLY ORIENTED ERN TROUGH. TROUGH ASSOCIATED WITH ID LOW WILL
BECOME PROGRESSIVELY MORE NEGATIVELY TILTED THROUGH REMAINDER
PERIOD...REACHING WRN CO AND CENTRAL WY WHILE PARENT CYCLONE ONLY
SLOWLY EJECTS TOWARD YELLOWSTONE AREA. MOISTURE CHANNEL IMAGERY
INDICATES MID/UPPER LOW OVER NRN INDIANA...ASSOCIATED WITH LARGER
SCALE ERN TROUGH. THIS FEATURE IS FCST TO MOVE SEWD ACROSS OH RIVER
TO NRN KY BY 12Z AND SUPPORT ISOLATED TSTMS...WHILE DOWNSTREAM
SHORTWAVE NOW OVER GA COAST AND SC EJECTS RAPIDLY EWD OVER ATLANTIC.

AT SFC...SEVERAL LOWS ARE EVIDENT ALONG PRONOUNCED FRONTAL ZONE THAT
EXTENDS FROM E-CENTRAL MT SWD THROUGH CENTRAL WY...THEN SWWD ACROSS
SERN UT AND WRN AZ. THIS FRONT IS FCST TO SURGE EWD THROUGH CENTRAL
ROCKIES OVERNIGHT AS PRIMARY SFC CYCLONE CONSOLIDATES ACROSS SERN
MT.

..NRN/CENTRAL HIGH PLAINS...
WIDELY SCATTERED TO SCATTERED TSTMS IN CLUSTERS -- SOME SVR -- WILL
CONTINUE FOR SEVERAL MORE HOURS ACROSS PORTIONS ERN MT...BECOMING
ISOLATED TO WIDELY SCATTERED FARTHER S ACROSS WY WHERE LOW LEVEL
FORCING IS SOMEWHAT WEAKER. ACTIVITY WILL REMAIN RATHER HIGH BASED
GIVEN SFC DEW POINTS UPPER 30S TO MID 40S. LARGE HAIL AND STG-SVR
GUSTS WILL REMAIN POSSIBLE. AS MID-UPPER TROUGH BECOMES MORE
NEGATIVELY TILTED...MEAN WIND VECTOR WILL BACK AND ATTAIN MORE
PRONOUNCED ELY COMPONENT...FROM NERN WY NWD THROUGH ERN MT. THIS IN
TURN WILL SUPPORT MERIDIONAL TO NWWD STORM MOTIONS -- MODULATED
SOMEWHAT BY SFC FORCING ASSOCIATED WITH NEWD-DIRECTED OUTFLOW POOLS
-- AND BY EXTENSION...KEEP SVR POTENTIAL FROM SPREADING MUCH FARTHER
EWD ACROSS NRN HIGH PLAINS.

SVR POTENTIAL WILL BE MORE SPORADIC WITH SWD EXTENT INTO CENTRAL
HIGH PLAINS...HOWEVER STRENGTHENING WIND FIELDS ALOFT AHEAD OF
MIDLEVEL TROUGH WILL ENSURE SUFFICIENT VERTICAL SHEAR FOR
SUPERCELLS. HOWEVER...ACTIVITY IS STRONGLY DIURNALLY DRIVEN...WITH
HEATING AND RESULTANT VERTICAL MIXING OF BOUNDARY LAYER REDUCING
CINH ENOUGH TO SUPPORT DEVELOPMENT. SBCINH SHOULD AGAIN INCREASE
RAPIDLY AS RELATIVELY DRY SFC AIR COOLS RAPIDLY AFTER SUNSET.
THERFORE TIME WINDOW WILL BE SHORT FOR SVR POTENTIAL FROM HIGH-BASED
TSTMS -- NOW EVIDENT IN VIS IMAGERY E OF FRONT/LARAMIE RANGES.
GIVEN LIMITED COVERAGE/DURATION OF POTENTIAL...WILL KEEP
PROBABILITIES MRGL.

.EDWARDS.. 04/19/2007

MESO: Mesoscale Discussion 0515

ACUS11 KWNS 182051
SWOMCD
SPC MCD 182051
WYZ000-MTZ000-182215-

MESOSCALE DISCUSSION 0515
NWS STORM PREDICTION CENTER NORMAN OK
0351 PM CDT WED APR 18 2007

AREAS AFFECTED...NRN WY AND SRN MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 182051Z - 182215Z

A SEVERE THREAT WILL LIKELY DEVELOP OVER NRN WY AND SRN MT OVER THE
NEXT FEW HOURS. LARGE HAIL WILL BE THE PRIMARY THREAT ALTHOUGH
ISOLATED WIND DAMAGE WILL ALSO BE POSSIBLE. A WW MAY BECOME
NECESSARY LATE THIS AFTERNOON ACROSS THE REGION.

LATEST SFC ANALYSIS SHOWS A SFC LOW NEAR RIVERTON WY WITH A COLD
FRONT EXTENDING SWD ACROSS SW WY INTO ERN UT. A LOW-LEVEL MOIST AXIS
EXISTS ACROSS WRN SD...ERN MT AND NE WY WHERE SFC DEWPOINTS RANGE
FROM THE 30S F TO THE LOWER 40S F. SFC HEATING ALONG THE MOIST AXIS
IS RESULTING IN INSTABILITY WITH MLCAPE VALUES GENERALLY AROUND 500
J/KG. IN ADDITION...RUC ANALYSIS AND WATER VAPOR IMAGERY SHOW A
SERIES OF SUBTLE SHORTWAVE TROUGHS EMBEDDED IN A LARGER WRN U.S.
UPPER-LEVEL TROUGH. AS THESE FEATURES MOVE NNEWD ACROSS THE REGION
WILL INCREASE LARGE-SCALE ASCENT PROVIDING A FOCUS FOR SCATTERED
THUNDERSTORM DEVELOPMENT OVER THE NEXT FEW HOURS. AS THUNDERSTORMS
INCREASE IN COVERAGE AND MATURE...MODERATE VERTICAL SHEAR AND LAPSE
RATES EXCEEDING 9.0 C/KM SHOWN ON FORECAST SOUNDINGS SHOULD BE
SUFFICIENT FOR ISOLATED SUPERCELLS WITH LARGE HAIL. WIND DAMAGE
SHOULD BE MORE ISOLATED BUT MAY ALSO ACCOMPANY ANY SUPERCELLS THAT
DEVELOP.

.BROYLES.. 04/18/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...UNR...CYS...BYZ...RIW...

43330757 43790910 44171040 44661072 45381067 45980996
46120879 45640682 45100554 44160444 42920478 42730615

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181952
SWODY1
SPC AC 181950

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0250 PM CDT WED APR 18 2007

VALID 182000Z - 191200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE HIGH PLAINS FROM ERN
MT INTO ERN WY...

..LOWER OH VALLEY...

DEEP CONVECTION HAS STRUGGLED TO DEVELOP WITHIN EXIT REGION OF UPPER
JET ACROSS IL/IND INTO KY THIS AFTERNOON. THOUGH ISOLATED
THUNDERSTORMS HAVE BEEN NOTED ACROSS SRN KY AT TIMES...BOUNDARY
LAYER APPEARS TO BE SOMEWHAT LACKING IN CONVERGENCE FARTHER NW IN
ADVANCE OF UPPER SPEED MAX. ADDITIONALLY...MID LEVEL LAPSE RATES
HAVE YET TO ADJUST SUFFICIENTLY FOR PARCELS TO ASCEND FREELY DESPITE
STRONG SFC HEATING. NET RESULT WILL BE FOR THE CONTINUATION OF
STRUGGLING UPDRAFTS WITH ONLY A FEW THUNDERSTORMS INTO THE EVENING
HOURS.

..LEE OF NRN/CNTRL ROCKIES...

DEEP LARGE SCALE FORCING IS SPREADING ACROSS ERN ID/UT/WRN WY THIS
AFTERNOON...PER EWD ADVANCEMENT OF THICKER CLOUD
SHIELD/PRECIPITATION. ISOLATED THUNDERSTORMS HAVE BEEN OBSERVED
WITHIN THIS STRONG BAROCLINIC ZONE ACROSS NWRN WY INTO SWRN
MT...THOUGH HAVE RECENTLY DECREASED IN COVERAGE/INTENSITY.
DOWNSTREAM...STRONG SFC HEATING IS UNDERWAY FROM NERN CO...NWD INTO
ERN MT WHERE SFC-3 KM LAPSE RATES ARE APPROACHING DRY ADIABATIC.
WITH THE BOUNDARY LAYER MOISTURE EXTREMELY LIMITED ACROSS THE HIGHER
TERRAIN OF WRN WY INTO ERN UT IT APPEARS STRONGER THUNDERSTORM
ACTIVITY MAY TEND TO DEVELOP JUST DOWNSTREAM WHERE SFC DEW POINTS
ARE APPROACHING 40F. PARCEL BUOYANCY IS MUCH STRONGER ACROSS THIS
REGION WITH MLCAPE VALUES NOW ON THE ORDER OF 500 J/KG ACROSS ERN WY
INTO SERN MT. ADDITIONALLY...LATEST VIS IMAGERY SUGGESTS CU FIELD
IS DEEPENING/EXPANDING FROM THE NRN SLOPES OF THE LARAMIE MOUNTAINS
NEAR CPR...NWD INTO EXTREME SERN MT. STRONG THUNDERSTORMS SHOULD
EVOLVE WITHIN THIS AGITATED CU FIELD WITHIN THE NEXT FEW HOURS.
DEEP LAYER SHEAR IS MORE THAN ADEQUATE FOR SUSTAINING ORGANIZED
ROTATING UPDRAFTS CAPABLE OF PRODUCING HAIL AND GUSTY WINDS. GIVEN
THE STRENGTH OF THE KINEMATIC FIELDS AND THE LIKELIHOOD FOR DEEP
SFC-BASED CONVECTION...SLIGHT RISK CERTAINLY SEEMS APPROPRIATE FOR
LARGE HAIL AND ISOLATED DAMAGING WINDS.

.DARROW.. 04/18/2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 181752
SWODY2
SPC AC 181750

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1250 PM CDT WED APR 18 2007

VALID 191200Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..WESTERN NC/SOUTH CAROLINA...

WELL DEFINED UPPER SPEED MAX WILL DIG SEWD ACROSS THE TN VALLEY INTO
ERN GA DURING THE AFTERNOON HOURS WHILE UPPER LOW SLOWLY LOSES
CIRCULATION IDENTITY OVER THE SRN APPALACHIANS. EVEN SO...VERY COLD
H5 TEMPERATURES...AOB MINUS 20C...WILL OVERSPREAD NW-SE ORIENTED LOW
LEVEL BAROCLINIC ZONE FROM ERN TN TO NEAR THE GA/SC COAST WHICH
SHOULD BE THE MAIN FOCUS FOR THUNDERSTORM DEVELOPMENT DURING THE
DAYLIGHT HOURS. IT APPEARS SUFFICIENT BOUNDARY LAYER MOISTURE WILL
HOLD ALONG THIS BAROCLINIC ZONE AS WARM SECTOR ACROSS GA HEATS
SUBSTANTIALLY DURING THE AFTERNOON HOURS. AS A RESULT...SFC-BASED
THUNDERSTORMS CAPABLE OF GENERATING MARGINALLY SEVERE HAIL SHOULD
DEVELOP/PROPAGATE SEWD ALONG THE SC/GA BORDER. DEEP LAYER SHEAR IS
ACTUALLY FORECAST TO BE STRONG ENOUGH TO WARRANT STORM
ROTATION...AND POSSIBLY WEAK SUPERCELL DEVELOPMENT...ESPECIALLY IF
SFC DEW POINTS CAN RISE INTO THE LOWER 50S AHEAD OF DEVELOPMENT.
WILL MONITOR THIS REGION FOR POSSIBLE UPGRADE IN LATER OUTLOOKS.

..NORTHERN/CENTRAL PLAINS...

STRONG SHORTWAVE TROUGH WITH SUBSTANTIAL HEIGHT FALLS WILL SPREAD
ACROSS WY INTO THE NRN HIGH PLAINS DURING THE DAY WHICH SHOULD FORCE
A WELL DEFINED COLD FRONT ACROSS THE DAKOTAS. A NARROW ZONE OF WEAK
INSTABILITY WILL DEVELOP JUST AHEAD OF THIS STRONGLY
CONVERGENT/FORCED WIND SHIFT. LATEST THINKING IS CONVECTION...WITH
A FEW ISOLATED THUNDERSTORMS...WILL EVOLVE IN ADVANCE OF THIS STRONG
SHORTWAVE. THOUGH FORECAST SOUNDINGS ARE NOT PARTICULARLY
UNSTABLE...SUFFICIENT BUOYANCY SHOULD EXIST FOR AT LEAST A LOW
PROBABILITY FOR GUSTY WINDS OR PERHAPS SOME HAIL.

FARTHER SOUTH ACROSS KS...WEAK RIDGING IN THE WAKE OF NRN PLAINS
SHORTWAVE TROUGH MAY SUPPRESS CONVECTIVE POTENTIAL ALONG TRAILING
FRONT DURING THE MID DAY HOURS. STRONG HEATING WILL BE NECESSARY
FOR DESTABILIZATION AND ANY HOPES FOR ROBUST CONVECTIVE DEVELOPMENT
ACROSS THIS REGION. UNTIL HIGHER QUALITY MOISTURE SURGES INTO WRN
KS LATE IN THE PERIOD IT WILL PROVE DIFFICULT DESTABILIZING THIS
REGION ADEQUATELY FOR SEVERE THUNDERSTORMS. A FEW STORMS MAY
HOWEVER EVOLVE WITHIN INCREASING WARM ADVECTION DURING THE EVENING
HOURS...A FEW OF WHICH MAY GENERATE SOME HAIL OR GUSTY WINDS.

.DARROW.. 04/18/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181551
SWODY1
SPC AC 181548

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1048 AM CDT WED APR 18 2007

VALID 181630Z - 191200Z

..NO SVR TSTM AREAS FORECAST...

VERY STRONG UPPER TROUGH CURRENTLY OVER NV IS FORECAST TO ROTATE
EASTWARD ACROSS THE CENTRAL/NORTHERN ROCKIES TODAY.
MEANWHILE...RAPID SURFACE CYCLOGENESIS IS EXPECTED ACROSS PARTS OF
MT/WY...WITH LEE TROUGH EXTENDING SOUTHWARD INTO EASTERN CO. LARGE
SCALE FORCING THROUGHOUT THIS REGION...COMBINED WITH FAVORABLE
/ALBEIT RELATIVELY DRY/ THERMODYNAMIC PROFILES WILL FAVOR SCATTERED
THUNDERSTORMS CAPABLE OF GUSTY WINDS AND HAIL OVER MUCH OF WY/MT/CO
AND PARTS OF EASTERN UT.

..WESTERN WY/CO AND EASTERN UT...
MORNING SURFACE ANALYSIS SHOWS LOW NORTH OF SLC...WITH STRONG COLD
FRONT SURGING EASTWARD ACROSS WESTERN UT. THIS FRONT WILL PROGRESS
EASTWARD TODAY INTO WESTERN WY/CO. FORECAST SOUNDINGS OVER THIS
REGION SHOW STEEP LOW/MID LEVEL LAPSE RATES AND STRONG SOUTHWEST
FLOW THROUGH A DEEP LAYER. DEEP MIXING WILL YIELD STRONG GRADIENT
WINDS...WHICH WILL ONLY BE ENHANCED THIS AFTERNOON AS SCATTERED
THUNDERSTORMS DEVELOP NEAR THE FRONT. COLD TEMPERATURES ALOFT COULD
ALSO RESULT IN HAIL IN STRONGER STORMS.

..EASTERN CO/WY AND MUCH OF MT...
BY LATE THIS AFTERNOON...LEE TROUGH IS FORECAST TO EXTEND FROM MAIN
SYNOPTIC LOW OVER EASTERN MT INTO EASTERN WY/CO. STRONG
SOUTHEASTERLY LOW LEVEL WINDS OVER THE HIGH PLAINS OF MT/WY/CO WILL
MAINTAIN SURFACE DEWPOINTS GENERALLY IN THE 30S TO LOWER 40S...AS
WELL AS RESULT IN FAVORABLE CONVERGENCE AND SHEAR PROFILES FOR
ISOLATED THUNDERSTORM DEVELOPMENT. CONVECTION WILL LIKELY INITIATE
FIRST NEAR LOW OVER SOUTH CENTRAL MT...SPREADING NORTHWARD ACROSS MT
THROUGH THE EVENING. THESE STORMS WILL HAVE A RISK OF GUSTY WINDS
AND HAIL. OTHER MORE ISOLATED ACTIVITY IS ANTICIPATED ALONG THE LEE
TROUGH AS FAR SOUTH AS EAST-CENTRAL CO. THESE STORMS WILL BE WIDELY
SPACED...BUT COULD BE HIGH-BASED SUPERCELLS CAPABLE OF LOCALLY
DAMAGING WINDS AND HAIL AS WELL. OVERALL COVERAGE OF SEVERE STORMS
DOES NOT APPEAR TO WARRANT A SLIGHT RISK AT THIS TIME. HOWEVER...WE
WILL CONTINUE TO MONITOR FOR GREATER DESTABILIZATION THAN CURRENTLY
EXPECTED.

..OH VALLEY...
WEAK SURFACE LOW IS CURRENTLY NEAR SDF...WITH COLD FRONT EXTENDING
WESTWARD INTO SOUTHERN IL/SOUTHEAST MO. LOW CLOUDS ALONG/AHEAD OF
FRONT ACROSS THE LOWER OH AND TN VALLEYS ARE SLOWLY ERODING...WHICH
SHOULD ALLOW POCKETS OF DAYTIME HEATING AND DESTABILIZATION.
DEWPOINTS IN THE 40S TO NEAR 50F WILL YIELD AFTERNOON MLCAPE VALUES
UP TO 500 J/KG. MODEL GUIDANCE IS CONSISTENT IN THE DEVELOPMENT OF
SCATTERED THUNDERSTORMS OVER PARTS OF IND/KY THIS AFTERNOON...WHERE
THE STRONGEST STORMS COULD PRODUCE HAIL. ORGANIZED SEVERE STORMS
ARE NOT ANTICIPATED AT THIS TIME.

.HART/GUYER.. 04/18/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181251
SWODY1
SPC AC 181248

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0748 AM CDT WED APR 18 2007

VALID 181300Z - 191200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
A LARGE SCALE OMEGA-TYPE BLOCKING PATTERN IS BECOMING ESTABLISHED
OVER N AMERICA WITH THE PRIMARY RIDGE AXIS FROM THE ERN PLAINS NWD
TO A DEVELOPING CLOSED HIGH OVER WRN ONTARIO. FLANKING RIDGE ARE A
DOWNSTREAM TROUGH INVOF THE ATLANTIC COAST...AND AN UPSTREAM MEAN
TROUGH OVER THE GREAT BASIN. WITHIN THE WRN MEAN TROUGH...ONE
STRONG SHORTWAVE TROUGH OVER NV THIS MORNING WILL MOVE EWD TO THE
CENTRAL ROCKIES THIS EVENING AND NEWD TO THE CENTRAL/NRN HIGH PLAINS
BY EARLY THURSDAY...AS ANOTHER UPSTREAM TROUGH APPROACHES NRN
CA/ORE. CYCLOGENESIS WILL OCCUR IN THE IMMEDIATE LEE OF THE NRN
ROCKIES IN ADVANCE OF THIS MID LEVEL WAVE...WHILE A COLD FRONT
SURGES EWD ACROSS CO/WY TO THE S OF THE SURFACE CYCLONE IN CENTRAL
MT.

..CO/WY/MT THIS AFTERNOON INTO TONIGHT...
THUNDERSTORMS WILL BE POSSIBLE TODAY FROM NRN UT/NWRN CO NWD INTO
SRN MT WHERE STRONG ASCENT IS EXPECTED ALONG THE DEEP LAYER
BAROCLINIC ZONE NOW PROGRESSING EWD INTO UT/ID. HOWEVER... LIMITED
LOW-LEVEL MOISTURE...AS WELL AS INCREASING CLOUDS AND RELATIVELY
EARLY ARRIVAL OF THE FRONT WILL TEND TO LIMIT INSTABILITY IN THIS
AREA. STRONG VERTICAL SHEAR AND STEEP LAPSE RATES COULD STILL
SUPPORT STORMS WITH STRONG WINDS TODAY. FARTHER E OVER THE HIGH
PLAINS...STRONGER SURFACE HEATING /AFTERNOON TEMPERATURES REACHING
65-75 F/ AND STEEP MID LEVEL LAPSE RATES WILL SUPPORT LATE AFTERNOON
MLCAPE VALUES AOA 500 J/KG FROM THE HIGH PLAINS OF N CENTRAL CO NWD
ACROSS ERN WY INTO SE MT...DESPITE BOUNDARY LAYER DEWPOINTS ONLY IN
THE MID-UPPER 30S. THUNDERSTORM COVERAGE SHOULD INCREASE OVER AND E
OF THE MOUNTAINS BY LATE EVENING AS THE COLD FRONT OVERTAKES THE LEE
TROUGH AND ASCENT INCREASES. THE INITIALLY SURFACE-BASED STORMS
SHOULD PERSIST AND SPREAD EWD OVER THE HIGH PLAINS AS ELEVATED
CONVECTION.

THE STEEP MID LEVEL LAPSE RATES AND RELATIVELY COOL MID LEVEL
TEMPERATURES...ALONG WITH INCREASING VERTICAL SHEAR FROM N TO S IN
CLOSER PROXIMITY TO THE MID LEVEL JET...SHOULD SUPPORT A FEW STORMS
WITH MARGINALLY SEVERE HAIL. ALSO...INVERTED-V PROFILES IN THE LOW
LEVELS SHOULD BE CONDUCIVE TO STRONG OUTFLOW WINDS AS THUNDERSTORM
COVERAGE INCREASES DURING THE EVENING.

..LOWER OH VALLEY THIS AFTERNOON...
A COMPLEX INTERACTION WILL OCCUR BETWEEN MULTIPLE MID LEVEL WAVES
OVER THE MS/OH VALLEYS AND THE SE STATES TODAY. THE SRN STREAM
TROUGH OVER THE LOWER MS VALLEY THIS MORNING WILL LOSE AMPLITUDE AND
ACCELERATE INTO THE CONFLUENT FLOW REGIME OFF THE SE ATLANTIC COAST
BY THIS EVENING. MEANWHILE...A COMPACT NRN STREAM CLOSED LOW OVER
SRN LAKE MI WILL ROTATE SWD TO THE LOWER OH VALLEY AS PART OF THE
LARGER SCALE TROUGH ON THE ERN FLANK OF THE OMEGA BLOCK. THE THICK
CLOUDS WITH THE SRN STREAM WAVE SHOULD CLEAR THE LOWER OH VALLEY BY
MIDDAY...ALLOWING SOME SURFACE HEATING OF THE BOUNDARY LAYER WITH
RESIDUAL DEWPOINTS OF 45-50 F NEAR A WEAK SURFACE LOW AND ALONG A
WEAK COLD FRONT MOVING SWD TOWARD THE OH RIVER. THOUGH TOTAL CAPE
SHOULD REMAIN AOB 500 J/KG AND VERTICAL SHEAR WILL BE WEAK...THE
RELATIVELY STEEP LAPSE RATES AND COLD MID LEVEL TEMPERATURES COULD
SUPPORT MARGINALLY SEVERE HAIL FOR A FEW HOURS THIS AFTERNOON.

.THOMPSON/GRAMS.. 04/18/2007

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 180856
SWOD48
SPC AC 180856

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0356 AM CDT WED APR 18 2007

VALID 211200Z - 261200Z

..DISCUSSION...
GFS AND ECMWF ARE REMARKABLY CONSISTENT IN HANDLING THE STRONG
SHORT-WAVE TROUGH EXITING THE ROCKIES/ENTERING THE PLAINS DAY 4
/SAT. APR. 21/. NOT ONLY ARE THE MODEL SOLUTIONS FROM THE CURRENT
RUN EXTREMELY SIMILAR...BUT A GREAT DEAL OF MODEL CONSISTENCY HAS
EXISTED FOR THE PAST SEVERAL DAYS IN DEPICTING THIS FEATURE MOVING
INTO THE CENTRAL CONUS FOR SAT. APR. 21.

THE BIGGEST NEGATIVE ATTM APPEARS TO BE THE DEGREE OF BOUNDARY-LAYER
MOISTURE RETURN...AS TRAJECTORIES OFF THE GULF/INTO TX REMAIN
ELY/ESELY AROUND A LARGE HIGH OVER THE ERN HALF OF THE CONUS/GULF OF
MEXICO. HAVING SAID THIS...CONFIDENCE REMAINS HIGH THAT THE
STRENGTH OF THE EJECTING TROUGH AND ASSOCIATED WIND FIELD WILL
SUPPORT A FAIRLY SIGNIFICANT SEVERE EVENT DESPITE THE POSSIBILITY OF
RELATIVELY LIMITED INSTABILITY. THEREFORE...WILL MAINTAIN A THREAT
FOR SAT. /DAY 4/ ACROSS A LARGE PORTION OF THE PLAINS.

THE POSSIBLE LACK OF MOISTURE MAY BECOME MORE OF A LIMITING FACTOR
FOR DAY 5...AS THE UPPER TROUGH EJECTS NEWD ACROSS THE PLAINS AND
EVENTUALLY ACROSS THE UPPER GREAT LAKES REGION. WHILE SOME SEVERE
POTENTIAL WILL EXIST INTO THE MID/UPPER MS AND LOWER OH VALLEYS AND
POSSIBLY THE UPPER GREAT LAKES...OVERALL DEGREE OF SEVERE MAY BE
LIMITED DUE TO AN OVERALL LACK OF FAVORABLE INSTABILITY.
THEREFORE...WILL NOT HIGHLIGHT THE POTENTIAL FOR A SIGNIFICANT EVENT
FOR DAY 5 ATTM.

MODEL DIVERGENCE INCREASES -- AT LEAST WITH RESPECT TO TIMING -- FOR
DAYS 6-8. WHILE BOTH MODELS BRING A STRONG TROUGH/CLOSED LOW INTO
THE CENTRAL AND SRN PLAINS DURING THIS TIME FRAME...THE GFS IS CLOSE
TO 24 HOURS FASTER WITH THIS FEATURE THAN THE ECMWF. THUS...WILL
REFRAIN ATTM FROM HIGHLIGHTING THE SEVERE POTENTIAL ASSOCIATED WITH
THIS FEATURE ATTM...THOUGH CONFIDENCE IS INCREASING THAT A SEVERE
EVENT WILL INDEED OCCUR SOMETIME IN THE DAY 6-8 TIME FRAME OVER THE
SRN PLAINS.

.GOSS.. 04/18/2007

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 180731
SWODY3
SPC AC 180729

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT WED APR 18 2007

VALID 201200Z - 211200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
LARGE-SCALE RIDGE WILL PREVAIL OVER THE CENTRAL CONUS THIS
PERIOD...UPSTREAM OF A TROUGH CENTERED OVER THE WRN ATLANTIC AND
DOWNSTREAM OF A SECOND TROUGH ADVANCING EWD ACROSS THE WRN CONUS.
THE WRN TROUGH IS FORECAST TO REMAIN TOO FAR W TO DIRECTLY AFFECT
THE CONVECTIVE POTENTIAL OVER THE PLAINS STATES THIS PERIOD...BUT
MODELS HINT THAT A WEAK LEAD IMPULSE WITHIN SWLY FLOW AHEAD OF THIS
FEATURE MAY TRAVERSE THE HIGH PLAINS. THIS COMBINED WITH THE LIKELY
PRESENCE OF A HIGH PLAINS DRYLINE -- AND POSSIBLY A WEAK W-E WARM
FRONT LIFTING NWD ACROSS KS/OK...COULD RESULT IN A FEW
ISOLATED/SEVERE STORMS THIS PERIOD.

..CENTRAL AND SRN HIGH PLAINS INTO SRN KS/NRN OK...
A SLOW NWD INCREASE IN BOUNDARY-LAYER DEWPOINTS SHOULD OCCUR INTO
OK/KS/THE CENTRAL AND SRN HIGH PLAINS THIS PERIOD...AS BROAD AREA OF
LOW-LEVEL SELY FLOW DEVELOPS AHEAD OF APPROACHING LARGE-SCALE
TROUGH. THIS COMBINED WITH DAYTIME HEATING AND STEEPENING LAPSE
RATES -- PARTICULARLY OVER THE HIGH PLAINS -- SUGGESTS MODERATE
DESTABILIZATION WILL OCCUR BY LATE AFTERNOON.

WHILE THE NAM FORECAST SOUNDINGS REVEAL THE MODELS TYPICAL BIAS OF
AGGRESSIVELY ERODING THE CAPPING INVERSION WHILE ALSO
MOISTENING/STEEPENING THE LAPSE RATES WITHIN THE BOUNDARY
LAYER...THE NAMKF SHOWS A STRONGER -- AND LIKELY MORE ACCURATE --
DEPICTION OF A MORE PERSISTENT CAP.

ALONG THESE SAME LINES...THE NAM MUCH MORE AGGRESSIVELY DEVELOPS
PRECIPITATION -- BOTH ALONG THE WARM FRONT OVER NERN OK/SERN
KS...AND ALONG THE DRYLINE. ATTM...IT APPEARS THAT CONVECTIVE
DEVELOPMENT WILL BE QUITE LIMITED -- PERHAPS TO JUST A FEW ISOLATED
CELLS. HAVING SAID THAT...ANY STORMS WHICH DO DEVELOP WOULD FIND
THEMSELVES IN AN ENVIRONMENT -- BOTH THERMODYNAMICALLY AND
KINEMATICALLY -- SUPPORTIVE OF SUPERCELLS. THEREFORE...WILL
INTRODUCE A 5%/CONDITIONAL SEVERE THREAT ACROSS THE CENTRAL AND SRN
HIGH PLAINS...AND EWD INTO OK/KS ALONG THE POSSIBLE WARM FRONT.

.GOSS.. 04/18/2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 180601
SWODY2
SPC AC 180559

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT WED APR 18 2007

VALID 191200Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
WHILE CYCLONIC FLOW ALOFT OVER THE ERN CONUS WILL CONTINUE TO SHIFT
EWD INTO THE ATLANTIC...LARGE/COMPLEX UPPER TROUGH WILL CONTINUE TO
INTENSIFY/EXPAND OVER THE WEST. A NEGATIVELY-TILTED SHORT-WAVE
TROUGH WITHIN THE EVOLVING LARGER-SCALE TROUGH WILL CONTINUE TO BE
SHUNTED NEWD ACROSS THE NRN PLAINS...AS IT IMPINGES ON THE RIDGE
OVER THE PLAINS. MEANWHILE...A SECOND/STRONGER SHORT-WAVE FEATURE
SHOULD MOVE RAPIDLY SSEWD ALONG THE W COAST.

AT THE SURFACE...LEE TROUGH IS FORECAST TO MOVE EWD INTO THE PLAINS
AND WEAKEN WITH TIME...BUT STILL MAY PROVIDE A FOCUS FOR SCATTERED
AFTERNOON STORMS.

..NRN PLAINS SEWD INTO THE MID MO VALLEY/KS/NRN OK...
SHOWERS AND A FEW THUNDERSTORMS SHOULD BE ONGOING AT THE START OF
THE PERIOD AHEAD OF LEE TROUGH/SHORT-WAVE UPPER FEATURE OVER THE NRN
HIGH PLAINS AND VICINITY. THIS CONVECTION SHOULD CONTINUE MOVING
EWD THROUGH THE DAY...LIKELY REMAINING WEAK DUE TO LIMITED
INSTABILITY.

FURTHER S...INSTABILITY SHOULD INCREASE...THOUGH SUBSIDENCE/CAPPING
WILL LIKEWISE INCREASE WITH SWD EXTENT WHERE THE UPPER RIDGE WILL
PREVAIL.

ATTM...IT APPEARS THAT SOMEWHERE BETWEEN THE STRONGER UVV TO THE N
AND STRONGER CAP TO THE S...A SMALL ZONE OF SUFFICIENT INSTABILITY
AND A WEAKENING CAP ON THE SRN FRINGES OF THE UPPER FEATURE MAY
ALLOW A FEW AFTERNOON STORMS TO DEVELOP -- MOST LIKELY ACROSS
CENTRAL AND ERN KS. WITH 500 J/KG MEAN-LAYER CAPE AND 40 TO 50 KT
DEEP-LAYER SHEAR...A FEW STRONGER/POSSIBLY-ROTATING STORMS MAY
EVOLVE. GIVEN CAP ISSUES AND LIKELIHOOD THAT STORMS WILL REMAIN
ISOLATED...WILL INTRODUCE ONLY 5% SEVERE PROBABILITY ATTM.
CONVECTION/SEVERE THREAT SHOULD DECREASE INTO THE EVENING WITH THE
ONSET OF DIURNAL STABILIZATION.

.GOSS.. 04/18/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 180542
SWODY1
SPC AC 180539

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1239 AM CDT WED APR 18 2007

VALID 181200Z - 191200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...

LARGE OMEGA BLOCKING PATTERN WILL CONTINUE ACROSS THE MID AND HIGH
LATITUDES OF N. AMERICA WITH AN UNDERCUTTING STREAM OF STRONGER
ZONAL FLOW FROM THE ERN PACIFIC ACROSS THE SRN STATES. WITHIN THIS
LARGER-SCALE REGIME...MID-LEVEL TROUGH CURRENTLY DIGGING OVER THE
PACIFIC NW INTO GREAT BASIN WILL SHIFT MORE EWD PRIOR TO EJECTING IN
NEGATIVE TILT FASHION INTO THE NRN AND CNTRL HIGH PLAINS.

IN THE LOW-LEVELS...A RELATIVELY STRONG PACIFIC COLD FRONT ATTENDANT
TO THIS UPPER SYSTEM WILL PUSH EWD THROUGH THE ROCKIES INTO ADJACENT
HIGH PLAINS. ASSOCIATED SURFACE LOW IS FORECAST TO DEEPEN AS IT
DEVELOPS FROM NWRN WY INTO SERN MT BY THURSDAY MORNING.

..NRN/CNTRL ROCKIES INTO HIGH PLAINS...

LOW-LEVEL AIR MASS IS EXPECTED TO REMAIN RELATIVELY DRY AHEAD OF
PACIFIC COLD FRONT WITH DEWPOINTS COMMONLY IN THE 20S AND 30S.
HOWEVER...DAYTIME HEATING COUPLED WITH DYNAMIC COOLING ASSOCIATED
WITH CONCENTRATED HEIGHT FALL CENTER AHEAD OF UPPER SYSTEM WILL
RESULT IN THE DEVELOPMENT OF STEEP LOW TO MID-LEVEL LAPSE RATES
WITHIN PRE-FRONTAL AIR MASS. EXPECT SBCAPES TO RANGE FROM 200-400
J/KG OVER PORTIONS OF NERN UT/CO...TO 500-900 J/KG OVER S-CNTRL INTO
SERN MT.

TSTMS WILL LIKELY INITIALLY DEVELOP BY EARLY TO MID AFTERNOON ALONG
FRONT OR IN IMMEDIATE POST-FRONTAL AIR MASS FROM S-CNTRL MT SWD INTO
WRN WY AND NERN UT. SUBSEQUENT STORM DEVELOPMENT WILL THEN OCCUR
OVER PORTIONS OF CNTRL/ERN PARTS OF MT/WY SWD INTO WRN/CNTRL CO
THROUGH THE REMAINDER OF THE AFTERNOON INTO TONIGHT. THE STEEP
LAPSE RATES COUPLED WITH INCREASING VERTICAL SHEAR INDICATE THE
POTENTIAL FOR A FEW ORGANIZED STORMS CAPABLE OF SEVERE HAIL AND
LOCALLY DAMAGING WINDS.

FORECAST SOUNDINGS AND PLAN VIEW PROGNOSTIC FIELDS INDICATE THAT THE
STRONGEST VERTICAL SHEAR WILL REMAIN UPSTREAM OF THE STRONGER
INSTABILITY IN PLACE OVER MT...LEAVING SOME UNCERTAINTY AS TO WHERE
THE GREATEST SEVERE WEATHER THREAT WILL LIKELY EXIST.
THEREFORE...LOW WIND/HAIL PROBABILITIES HAVE BEEN ASSIGNED TO A
BROADER GEOGRAPHICAL AREA TO ADDRESS THIS UNCERTAINTY.

..WRN/CNTRL KY...

MID-LEVEL COLD POOL ATTENDANT TO UPPER LOW OVER THE OH VALLEY IS
EXPECTED TO CONTRIBUTE TO STEEPENING LAPSE RATES AND WEAK CONVECTIVE
INSTABILITY /SBCAPES OF 400-600 J PER KG/ INVOF WEAK SURFACE LOW AND
FRONT THIS AFTERNOON. ISOLATED/SCATTERED TSTMS WILL BECOME
INCREASINGLY LIKELY BY AFTERNOON ACROSS THE AREA...A FEW OF WHICH
COULD PRODUCE SOME SMALL HAIL. ANY SEVERE WEATHER THREAT APPEARS
TOO LOW TO WARRANT INCLUSION OF PROBABILITIES.

.MEAD/GRAMS.. 04/18/2007

Tuesday, April 17, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 180053
SWODY1
SPC AC 180051

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 PM CDT TUE APR 17 2007

VALID 180100Z - 181200Z

..THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF ERN TX
TONIGHT...

..NRN/CNTRL TX INTO THE ARKLATEX...

CONSIDERABLE COLD POOL GENERATION HAS LED TO THE DEVELOPMENT OF A
QUASI-LINEAR MCS OVER N TX THIS AFTERNOON AND EVENING WITH LEADING
EDGE OF SYSTEM EXTENDING ALONG THE I-35 CORRIDOR FROM THE TX/OK
BORDER SWD TO NEAR TPL AS OF 0030Z. 00Z FTW SOUNDING INDICATES THE
PRESENCE OF A RELATIVELY DEEP...SATURATED LAYER FROM THE SFC-700
MB...THOUGH WEAK LAPSE RATES WERE LIMITING MLCAPES TO 300-400 J/KG.
MOREOVER...STRONGEST VERTICAL SHEAR WAS OBSERVED NEAR AND ABOVE THE
EL HEIGHT WITH ONLY MODEST WIND FIELDS THROUGH THE LOWEST 6 KM AGL.

LARGE-SCALE FORCING FOR ASCENT AHEAD OF UPPER SYSTEM TRANSLATING
THROUGH THE RED RIVER VALLEY...COUPLED WITH COLD POOL INTERACTION
WITH A MOIST AND MARGINALLY UNSTABLE AIR MASS SHOULD MAINTAIN
ONGOING MCS THROUGH THE REGION TONIGHT WITH A CONTINUED THREAT OF
MARGINALLY SEVERE HAIL AND/OR LOCALLY DAMAGING WINDS.

FARTHER TO THE SE...A SECONDARY LINE OF CONVECTION WAS OBSERVED FROM
W OF CLL TO NEAR BAZ AS OF 0030Z...ON THE IMMEDIATE CYCLONIC SIDE OF
70 KT MID-LEVEL JET STREAK OVER S TX. WHILE CURRENT LEDBETTER TX
PROFILER INDICATES A VERTICAL SHEAR PROFILE SUPPORTIVE OF ORGANIZED
SEVERE STORMS...INCLUDING SUPERCELLS...WARM MID-LEVEL TEMPERATURES S
OF JET STREAK AXIS /REF 00Z CRP SOUNDING/ WILL LIKELY LIMIT THE
POTENTIAL INSTABILITY WITHIN INFLOW AIR MASS OF THIS SECONDARY
CONVECTIVE LINE.

.MEAD.. 04/18/2007

WATCHES: Severe Thunderstorm Watch - Number 151

WWUS20 KWNS 180011
SEL1
SPC WW 180011
TXZ000-180100-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH - NUMBER 151
NWS STORM PREDICTION CENTER NORMAN OK
711 PM CDT TUE APR 17 2007

THE NWS STORM PREDICTION CENTER HAS CANCELLED
SEVERE THUNDERSTORM WATCH NUMBER 151 ISSUED AT 140 PM CDT FOR PORTIONS OF

TEXAS

MESO: Mesoscale Discussion 0514

ACUS11 KWNS 172223
SWOMCD
SPC MCD 172222
TXZ000-172345-

MESOSCALE DISCUSSION 0514
NWS STORM PREDICTION CENTER NORMAN OK
0522 PM CDT TUE APR 17 2007

AREAS AFFECTED...N CNTRL TX

CONCERNING...SEVERE THUNDERSTORM WATCH 151...

VALID 172222Z - 172345Z

SEVERE WEATHER THREAT FOR REMAINING PORTIONS OF SEVERE THUNDERSTORM
WATCH 151 CONTINUES. ANOTHER WW EAST OF WW 151 IS UNLIKELY UNLESS
CONVECTIVE TRENDS DICTATE OTHERWISE.

LINE OF STORMS CONTINUES FROM NRN PORTIONS OF N CNTRL TX SWD INTO
CNTRL TX NEAR SAN SABA MOVING EAST AT AROUND 30 KT. OTHER STORMS
EXIST FARTHER S NEAR BLANCO. LATEST OBJECTIVE ANALYSIS SHOWS ONLY A
NARROW AXIS OF MARGINAL SBCAPE LEFT AHEAD OF LINE WHERE THE BOUNDARY
LAYER EXPERIENCED HEATING EARLIER TODAY. FARTHER EAST ACROSS THE
REMAINDER OF N CNTRL AND CNTRL TX...PERSISTENT LOW CLOUDS HAVE
RESULTED IN A STABLE LAYER NEAR THE SURFACE.

STORMS SHOULD CONTINUE DEVELOPING TONIGHT INTO N CNTRL AND CNTRL TX
ALONG EWD ADVANCING OUTFLOW BOUNDARY AND ZONE OF ASCENT ASSOCIATED
WITH VORT MAX. STEEPER LAPSE RATES IN THE 700-500 MB LAYER WILL
SPREAD EAST ABOVE THE RELATIVELY STABLE BOUNDARY LAYER. SOME THREAT
FOR HAIL AND WIND MAY PERSIST EWD INTO PARTS OF N CNTRL AND CNTRL
TX. HOWEVER...WEAK INSTABILITY WITHIN THE LOWEST 3 KM SHOULD LIMIT
OVERALL SEVERE POTENTIAL EAST OF WW 151.

.DIAL.. 04/17/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...EWX...

33419694 32499623 30599749 30279857 31379829 32119862
32799845 33309789

MESO: Mesoscale Discussion 0513

ACUS11 KWNS 171959
SWOMCD
SPC MCD 171959
TXZ000-OKZ000-172200-

MESOSCALE DISCUSSION 0513
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT TUE APR 17 2007

AREAS AFFECTED...TX S PLAINS...LOW ROLLING PLAINS...WRN N TX

CONCERNING...SEVERE THUNDERSTORM WATCH 151...

VALID 171959Z - 172200Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 151
CONTINUES.

19Z SFC ANALYSIS PLACES A LOW OVER KLBB WITH A DRYLINE SWD TO EAST
OF KMAF. A SECOND DRYLINE WAS LOCATED FROM JUST WEST OF KDYS SWD TO
EAST OF KJCT. A COLD POOL WAS EXPANDING SEWD FROM SWRN OK INTO WRN
N TX NEAR KSPS TO KDYS...THEN NWWD TO NEAR KLBB. A WARM FRONT
EXTENDED EWD FROM THE COLD POOL INTO NCNTRL TX.

TSTMS THAT DEVELOPED VCNTY THE SFC LOW OVER THE TX S PLAINS APPEAR
TO BE WEAKENING OWING TO EXPANDING COLD POOLS...DESTRUCTIVE STORM
SCALE INTERACTIONS. THUS...IT APPEARS THAT THE NON-SUPERCELL
TORNADO THREAT HAS DIMINISHED AS THE STORMS WEAKEN.

WARM SECTOR ALONG/E OF THE ERN DRYLINE AND SOUTH OF THE EXPANDING
COLD POOL HAD WARMED INTO THE UPR 60S-LWR 70S WITH A SURGE OF SFC
DEW POINTS OF 57-62 DEG F AT 19Z. AS COLDER AIR ALOFT CONTINUES TO
SPREAD EWD...CINH WILL WEAKEN AND TSTMS DEVELOPING NEAR/NW OF KABI
WILL LIKELY GROW STRONGER. RECENT GUST TO 40 KTS AT KGDP SUGGESTS
THAT THE VERTICAL SHEAR WILL INCREASE OVER THE REGION AS MID-LEVEL
JET PUNCHES EWD...SUPPORTING AN ISOLD SUPERCELL OR TWO. BUT...THE
PRIMARY STORM MODE SHOULD GENERALLY BE MULTICELL CLUSTERS/SHORT LINE
SEGMENTS AS COLD POOLS MERGE AND STORMS SEED NEIGHBORING STORMS.
GIVEN THE STEEPENING LAPSE RATES ALOFT...LARGE HAIL WILL BE THE
PRIMARY THREAT...THOUGH DAMAGING WINDS MAY OCCUR AS WELL.
THERMODYNAMIC SET-UP APPEARS FAVORABLE FOR LARGE ACCUMULATIONS OF
HAIL WITH SOME STORMS.

THROUGH 21-22Z...THE PRIMARY SVR THREAT APPEARS TO BE MAXIMIZED IN
THE KABI-KSEP-KBWD REGION. BOUNDARY LAYER HAS WARMED THE MOST IN
THIS AREA AND WILL BE CLOSER TO THE STRONGER VERTICAL SHEAR. IN
FACT...ISOLD TSTMS MAY FORM AS FAR S AS THE HILL COUNTRY. FARTHER
NE...AIR MASS MAY RECOVER SOME NEAR/W OF KFTW...SUPPORTING AN
INCREASING SVR RISK THERE LATER THIS AFTN.

.RACY.. 04/17/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...OUN...EWX...SJT...LUB...MAF...

33940206 34440184 34669948 33809774 31879740 31059810
30829944 31160123 32060192 33070197

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171924
SWODY1
SPC AC 171922

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0222 PM CDT TUE APR 17 2007

VALID 172000Z - 181200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF NWRN/NCNTRL
TX...

..SOUTHERN PLAINS...

LATEST SATELLITE IMAGERY CLEARLY DEPICTS CENTER OF LARGE SCALE UPPER
LOW SHIFTING EAST INTO THE TX SOUTH PLAINS...JUST SW OF LBB.
STRONGEST FLOW HAS NOW ROUNDED THE BASE OF THE TROUGH AND IS
EJECTING EWD ACROSS THE EDWARDS PLATEAU. ALONG/NORTH OF THIS SPEED
MAX...ROUGHLY ALONG/JUST SOUTH OF THE TRACK OF THE UPPER LOW...VERY
COLD MID LEVEL TEMPERATURES WILL OVERSPREAD RECOVERING/MOISTENING
WARM SECTOR. PARTIAL CLEARING IS EVIDENT WEST OF I-35 WHERE
TEMPERATURES HAVE NOW REBOUNDED INTO THE 60S...WITH DEW POINTS AOA
MID 50S.

THUNDERSTORMS HAVE RECENTLY EXPANDED IN INTENSITY/AREAL COVERAGE
BENEATH THE UPPER LOW WITH MANY UPDRAFTS NOW LIKELY PRODUCING LARGE
HAIL ACROSS THE TX SOUTH PLAINS. CONDITIONS FAVORABLE FOR SEVERE
HAIL SHOULD GRADUALLY SPREAD EAST ACROSS NCNTRL TX THIS
AFTERNOON...WITH TIME A FEW SUPERCELLS SHOULD EVOLVE...ESPECIALLY
ACROSS THE ERN HALF OF WW151 WHERE DEEP LAYER SHEAR IS NOTICEABLY
STRONGER. ADDITIONALLY...A FEW BRIEF TORNADOES MAY ACCOMPANY THE
STRONGER UPDRAFTS INVOF UPPER LOW WHERE VORTICITY IS MAXIMIZED
ACROSS THE HIGH PLAINS. HOWEVER...MAIN THREAT SHOULD BE LARGE HAIL.

.DARROW.. 04/17/2007

WATCHES: Severe Thunderstorm Watch Number 151

WWUS20 KWNS 171838
SEL1
SPC WW 171838
TXZ000-180100-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 151
NWS STORM PREDICTION CENTER NORMAN OK
140 PM CDT TUE APR 17 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

WESTERN NORTH TEXAS

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 140 PM UNTIL
800 PM CDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 80
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 115 MILES WEST
NORTHWEST OF ABILENE TEXAS TO 15 MILES EAST NORTHEAST OF
STEPHENVILLE TEXAS. FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...SCATTERED THUNDERSTORMS ARE INCREASING OVER WEST TX IN
REGION OF STRONG DAYTIME HEATING AND STEEP LOW LEVEL LAPSE RATES.
CLEARING SKIES ARE EXPECTED TO DEVELOP EASTWARD ACROSS WATCH AREA
THIS AFTERNOON...WITH STORMS ALSO SPREADING ACROSS REGION. LARGE
HAIL IS LIKELY DUE TO COLD MID LEVEL TEMPERATURES. POTENTIAL ALSO
EXISTS FOR ISOLATED LANDSPOUTS GIVEN FAVORABLE THERMODYNAMIC AND
AMBIENT VORTICITY PATTERN.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 27030.

..HART

MESO: Mesoscale Discussion 0512

ACUS11 KWNS 171747
SWOMCD
SPC MCD 171747
TXZ000-171945-

MESOSCALE DISCUSSION 0512
NWS STORM PREDICTION CENTER NORMAN OK
1247 PM CDT TUE APR 17 2007

AREAS AFFECTED...S PLAINS OF W TX...LOW ROLLING PLAINS...NCNTRL
TX...WRN N TX

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 171747Z - 171945Z

..INCREASING SEVERE PROBABILITIES EXPECTED OVER THE REGION THROUGH
THE AFTN...

17Z SFC ANALYSIS PLACES A 1009 MB LOW NW OF KLBB WITH A WARM FRONT
EXTENDING E TO JUST S OF THE RED RVR VLY. DOUBLE STRUCTURE DRYLINE
EXTENDS S...BUT WILL CONSOLIDATE ALONG A LINE FROM JUST E OF
KLBB-KSWW-KJCT BY 20Z. THE LOW WILL LIKELY DEVELOP EWD ALONG THE
WARM FRONT INTO WRN N TX BY LATE AFTN.

TSTMS HAVE BEEN DEVELOPING VCNTY THE SFC LOW SWD ALONG THE DRYLINE
WHERE MORNING STRATUS DISSOLVED EARLIER. THESE STORMS ARE LIKELY
HIGH-BASED AND EXIST IN A LIGHTER FLOW REGIME ALOFT BENEATH THE UPR
LOW. EARLY INITIATION WILL LIKELY YIELD HAIL...OR PERHAPS AN ISOLD
TORNADO.

PRIMARY MOIST AXIS EXISTS ACROSS CNTRL TX AND WILL CONTINUE
ADVECTING NWD INTO THE HILL COUNTRY AND TOWARD WRN N TX LATER THIS
AFTN. RUC FCST SOUNDINGS SUGGEST THAT SFC TEMPS AOA 65 DEG F WILL
BE NEEDED FOR A SFC-BASED STORM...AS THE COLD AIR ALOFT SPREADS EWD.
VSBL SATL SHOWS BINOVC OCCURRING ACROSS THE LOW ROLLING
PLAINS...AND THE CINH SHOULD WEAKEN CONSIDERABLY BY 19-20Z. AS A
RESULT...STORMS UPSTREAM...AND OTHERS DEVELOPING DOWNSTREAM ALONG
THE DRYLINE...WILL LIKELY GROW UPSCALE INTO STRONGER TSTMS.

WLY SFC FLOW HAS INCREASED OVER THE TRANS-PECOS...INDICATIVE OF THE
STRONGER FLOW ALONG THE BASE OF THE TROUGH EJECTING EWD. THIS WILL
BOOST VERTICAL SHEAR DOWNSTREAM AND THE STORMS LATER THIS AFTN WILL
GROW INTO SUPERCELLS WITH LARGE HAIL LIKELY. ACTIVITY WILL
EVENTUALLY SPREAD ESEWD INTO THE PARTS OF NCNTRL TX BY LATE
AFTN...INCLUDING THE DFW METROPLEX. A STRONG CAP WILL EXIST
DOWNSTREAM...POSSIBLY WEAKENING AS THE COLDER AIR ALOFT ARRIVES. AT
THE VERY LEAST...LARGE HAIL WILL BE A THREAT...BUT IF SUFFICIENT
HEATING/WEAKENING CINH CAN OCCUR...DAMAGING WINDS COULD ALSO OCCUR
WITH MORE SFC-BASED STORMS.

.RACY.. 04/17/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...OUN...SJT...LUB...MAF...

34110184 33909915 33369720 32679671 31629660 31359764
31489864 32220072 32740214 33370256 33850240

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 171727
SWODY2
SPC AC 171726

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT TUE APR 17 2007

VALID 181200Z - 191200Z

..NO SVR TSTM AREAS FORECAST...

..NRN HIGH PLAINS...

12Z MODEL GUIDANCE IS GENERALLY CONSISTENT REGARDING PROGRESSION OF
UPPER TROUGH ACROSS THE INTERMOUNTAIN REGION INTO THE NRN/CNTRL
ROCKIES BY LATE AFTERNOON. THIS FEATURE WILL UNDOUBTEDLY ENHANCE
LARGE SCALE CONVERGENCE/ASCENT ACROSS MUCH OF MT/WY AS EXIT REGION
OF UPPER JET SHIFTS INTO ERN WY. FORECAST SOUNDINGS SUGGEST
BOUNDARY LAYER WILL HEAT MARKEDLY ACROSS THE HIGH PLAINS IN THE LEE
OF THE MT/WY ROCKIES WHERE LOWEST 3 KM LAPSE RATES SHOULD APPROACH 9
C/KM. IN SITU MOISTURE IN THE WAKE OF LOW LATITUDE TROUGH SHOULD
RETURN NWWD AS LLJ STRENGTHENS FROM THE NEB PANHANDLE INTO ERN WY.
THIS WILL PROVIDE AMPLE MOISTURE FOR HIGH BASED CONVECTION AHEAD OF
COLD FRONT BY LATE AFTERNOON. GIVEN THE STRONG DEEP LAYER
SHEAR...ANY STORMS THAT DEVELOP WILL HAVE THE PROPENSITY TO
ROTATE...THOUGH POTENTIAL INSTABILITY WILL BE SOMEWHAT LACKING.
GUSTY WINDS AND MARGINALLY SEVERE HAIL MAY ACCOMPANY THIS ACTIVITY.

..EAST OF THE MS RIVER...

LOWER MS VALLEY SPEED MAX/TROUGH WILL EJECT QUICKLY EWD ALONG THE
GULF COAST AND DEAMPLIFY AS UPPER TROUGH OVER MI SAGS SWD INTO THE
OH VALLEY. BOUNDARY LAYER MOISTURE/INSTABILITY HAVE BEEN SCOURED
ACROSS THE GULF COAST AND INSTABILITY WILL BE GREATLY MINIMIZED
AHEAD OF QUICK MOVING TROUGH. A FEW THUNDERSTORMS COULD EVOLVE
ALONG WEAKLY CONVERGENT ZONE FROM SRN MS INTO THE NRN FL. HOWEVER
THE PROSPECT FOR ORGANIZED SEVERE CONVECTION IS MEAGER AT BEST.

FARTHER NORTH...A POCKET OF STEEP LAPSE RATES WILL DEVELOP AND DRIFT
SOUTH ACROSS IL/IND INTO KY. IT APPEARS SUFFICIENT CONVERGENCE WILL
EXIST ACROSS THE LOWER OH VALLEY REGION FOR A FEW THUNDERSTORMS
WITHIN EXIT REGION OF DIGGING SPEED MAX. THIS ACTIVITY WILL BE
STRONGLY DIURNAL IN NATURE AND SHOULD WEAKEN WITH LOSS OF HEATING.

.DARROW.. 04/17/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171631
SWODY1
SPC AC 171629

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT TUE APR 17 2007

VALID 171630Z - 181200Z

..THERE IS A SLGT RISK OF SVR TSTMS NORTHWEST AND NORTH CENTRAL
TX...

..TX...
STRONG UPPER LOW IS TRACKING EASTWARD THIS MORNING ACROSS NM INTO
WEST TX. THIS FEATURE IS FORECAST TO BE OVER WESTERN MS BY WED
MORNING. STRONG SOUTHERLY LOW LEVEL WINDS AHEAD OF SYSTEM WILL
TRANSPORT AIR MASS CURRENTLY OVER THE MID TX GULF COAST REGION
NORTHWARD INTO WESTERN NORTH TX THIS AFTERNOON. HOWEVER...THIS AIR
MASS IS ONLY MARGINALLY MOIST/UNSTABLE DUE TO RECENT INTRUSION OF
COLD AIR. SURFACE DEWPOINTS IN THE 50S TO NEAR 60F ARE POSSIBLE AS
FAR NORTHWEST AS SPS/ABI THIS AFTERNOON.

VISIBLE SATELLITE IMAGERY SHOWS RAPID CLEARING OCCURRING OVER PARTS
OF WEST TX...BENEATH STEEP MID LEVEL LAPSE RATES. THIS WILL HELP
DRYLINE MIX EASTWARD IN WEST-CENTRAL TX BY MID AFTERNOON. MORNING
OBSERVED AND RECENT AMDAR SOUNDING DATA SUGGEST A PRONOUNCED CAPPING
INVERSION WILL SUPPRESS DEEP CONVECTION THROUGH MUCH OF THE DAY.
HOWEVER...ALL MODEL GUIDANCE INDICATES THAT STRENGTHENING FORCING
FOR ASCENT WILL HELP ERODE CAP AND LEAD TO SCATTERED THUNDERSTORMS
AFTER 18Z.

INITIAL STORMS MAY FORM IN POST-DRYLINE AIR MASS OVER WEST TX.
THESE HIGH-BASED STORMS WILL LIKELY BUILD EASTWARD INTO MORE MOIST
LOW LEVEL AIR MASS AND INTENSIFY FROM SOUTHEAST OF CDS TO NEAR SJT.
ACTIVITY WILL THEN DEVELOP SOUTHEASTWARD DURING THE AFTERNOON AND
EVENING ACROSS OUTLOOK AREA. COLD TEMPERATURES ALOFT AND STEEP
LAPSE RATES WILL PROMOTE A RISK OF LARGE HAIL. ALSO...DEEP LAYER
SHEAR WILL BE SUPPORTIVE OF ORGANIZED MULTICELL OR OCCASIONAL
SUPERCELL STORMS CAPABLE OF DAMAGING WINDS. ISOLATED TORNADOES
CANNOT BE RULED OUT...BUT OVERALL RISK APPEARS RATHER MINIMAL DUE TO
LIMITED MOISTURE...AND EXTENSIVE CLOUD COVER OVER NORTHWEST TX WHERE
NEAR-SURFACE AMBIENT VORTICITY IS FORECAST.

.HART/GUYER.. 04/17/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171239
SWODY1
SPC AC 171237

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0737 AM CDT TUE APR 17 2007

VALID 171300Z - 181200Z

..THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO EARLY TONIGHT ACROSS
NW INTO N CENTRAL AND NE TX...

..SYNOPSIS...
A CLOSED MID LEVEL LOW OVER SW NM THIS MORNING WILL MOVE EWD INTO N
TX BY THIS EVENING AND THE LOWER MS VALLEY EARLY WED...AS AN
UPSTREAM TROUGH MOVES FROM THE PAC NW TO THE NRN GREAT BASIN. AT
THE SURFACE...A WEAK CYCLONE WILL ACCOMPANY THE SRN STREAM MID LEVEL
LOW FROM W CENTRAL INTO CENTRAL/N TX TODAY...WHILE THE ENTIRE SYSTEM
WILL BEGIN TO EVOLVE INTO MORE OF AN OPEN WAVE AND LOSE AMPLITUDE
OVERNIGHT.

..NW AND N CENTRAL TX THIS AFTERNOON...
A CORE OF STEEP L0W-MID LEVEL LAPSE RATES WILL SPREAD EWD FROM NM
INTO WRN AND CENTRAL TX BY THIS AFTERNOON IN ASSOCIATION WITH THE
MID LEVEL COLD POOL. HOWEVER...THE STEEPEST LAPSE RATES WILL BE
LIMITED TO A RELATIVELY SMALL AREA S AND W OF THE COMMA SHAPED ARC
OF CLOUDS/RAIN THAT WILL DEVELOP NEWD INTO OK TODAY IN ASSOCIATION
WITH A LEAD SHORTWAVE TROUGH ROTATING NEWD FROM W TX TOWARD SW OK.
THE PRIMARY SEVERE STORM THREAT TODAY IS EXPECTED TO EVOLVE FROM
THUNDERSTORM DEVELOPMENT BY MIDDAY INVOF THE TRIPLE POINT...ON THE
NE EDGE OF THE STEEPEST LOW-LEVEL LAPSE RATES/STRONGER SURFACE
HEATING AND THE NW EDGE OF THE BOUNDARY LAYER DEWPOINTS IN THE 50S.
THE SEVERE THREAT WILL BE FOCUSED FROM ABOUT 18-00Z ACROSS NW AND N
TX...WHILE THE SEVERE STORM THREAT SHOULD DECREASE AFTER SUNSET AS A
RESULT OF DIMINISHING LAPSE RATES WITH EWD EXTENT.

FORECAST SOUNDINGS /SUPPORTED BY UPSTREAM OBSERVATIONS/ SHOW RATHER
LARGE LOW-MID LEVEL BUOYANCY AND LOW EQUILIBRIUM LEVEL HEIGHTS OF
ONLY 7-8 KM AGL ACROSS N TX THIS AFTERNOON...AND RATHER MODEST
VERTICAL SHEAR THROUGH THE CLOUD LAYER IN THE REGION OF STRONGER
INSTABILITY. THE NET RESULT SHOULD BE ONE OR TWO CLUSTERS OF
VIGOROUS BUT RELATIVELY LOW-TOPPED STORMS CAPABLE OF PRODUCING LARGE
HAIL AND GUSTY OUTFLOW WINDS. THERE IS SOME POTENTIAL FOR
SUPERCELLS ON THE ERN EDGE OF THE INSTABILITY AND THE CYCLONIC SIDE
OF THE MID-UPPER JET...BUT THE THREAT FOR CLASSIC SUPERCELL
TORNADOES APPEARS QUITE MARGINAL. A COUPLE OF NON-MESOCYCLONE
TORNADOES MAY OCCUR IN CONJUNCTION WITH STEEP LOW-LEVEL LAPSE RATES
AND ENHANCED VERTICAL VORTICITY INVOF THE TRIPLE POINT THIS
AFTERNOON.

.THOMPSON/GRAMS.. 04/17/2007

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 170900
SWOD48
SPC AC 170859

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0359 AM CDT TUE APR 17 2007

VALID 201200Z - 251200Z

..DISCUSSION...
LONG-RANGE MODELS REMAIN CONSISTENT IN BRINGING A
STRONG/NEGATIVELY-TILTED UPPER TROUGH INTO THE PLAINS STATES ON OR
AROUND DAY 5 /SAT. APR. 21/...WHERE A LARGE/UNSTABLE WARM SECTOR
SHOULD BE IN PLACE.

MODELS HAVE BEGUN TO DIFFER THOUGH WITH RESPECT TO TIMING OF THE
TROUGH -- PARTICULARLY BEYOND DAY 5. THE ECMWF DEPICTS A STRONGER
DOWNSTREAM RIDGE OVER THE CENTRAL AND ERN CONUS LEADING UP TO DAY
5...AND THUS IS SLOWER WITH THE EWD PROGRESSION OF -- AND FURTHER N
WITH THE EVENTUAL EJECTION OF -- THIS FEATURE. MEANWHILE...THE GFS
IS FASTER/MORE PROGRESSIVE WITH THE TROUGH...AS IT IMPINGES ON A
WEAKER CENTRAL U.S. RIDGE.

WHILE THE GFS WOULD SUGGEST THAT A SEVERE THREAT MAY DEVELOP OVER
PARTS OF KS/OK/THE TX AND OK PANHANDLES ON DAY 4 -- FOLLOWED BY WHAT
SHOULD BE A FAIRLY WIDESPREAD/SIGNIFICANT EVENT DAY 5...THE SLOWER
ECMWF WOULD SUGGEST THAT THE MAIN EVENT WOULD OCCUR DAY 5...AND
POSSIBLY COULD LINGER INTO DAY 6 FURTHER E/NE.

ATTM...WILL MAINTAIN A DAY 5 OUTLOOK AREA -- THOUGH UNCERTAINTY
PRECLUDES CARRYING A DAY 4 AREA OVER THE WRN PLAINS...OR A DAY 6
AREA INTO THE ERN PLAINS/MID AND UPPER MS VALLEY.

AFTER DAYS 5-6...MODEL DIVERGENCE BECOMES MORE PRONOUNCED. WHILE
BOTH MODELS BRING A SECOND/VERY STRONG TROUGH INTO THE CENTRAL U.S.
IN THE DAY 7-8 TIME FRAME...THE LOCATION/TIMING/INTENSITY OF THE
FEATURE VARIES SIGNIFICANTLY BETWEEN THE TWO MODELS.
THEREFORE...DESPITE WHAT APPEARS TO BE A SECOND SEVERE EVENT
POSSIBLE FOR EARLY NEXT WEEK...PREDICTABILITY DURING THIS TIME FRAME
IS TOO LOW TO WARRANT THE INCLUSION OF A DAY 7/8 OUTLOOK.

.GOSS.. 04/17/2007

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 170720
SWODY3
SPC AC 170718

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0218 AM CDT TUE APR 17 2007

VALID 191200Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
AMPLIFIED UPPER FLOW PATTERN OVER NOAM FORECAST TO CONTINUE THROUGH
DAY 3...WITH A WRN U.S. TROUGH...AND ERN U.S./WRN ATLANTIC
TROUGH...AND A RIDGE IN BETWEEN -- CENTERED OVER ONTARIO/SRN HUDSON
BAY REGION THROUGH THE PERIOD.

LACK OF APPRECIABLE INSTABILITY ACROSS MOST OF THE CONUS SHOULD
GENERALLY PRECLUDE THUNDERSTORMS. GREATEST INSTABILITY IS
ANTICIPATED OVER THE CENTRAL CONUS -- INVOF KS/OK -- WHERE AROUND
500 J/KG MEAN-LAYER CAPE MAY DEVELOP. HOWEVER...BOUNDARY LAYER
SHOULD REMAIN CAPPED -- WITH LARGE-SCALE SUBSIDENCE FORECAST TO
PREVAIL BENEATH UPPER RIDGE. THOUGH A FEW STORMS MAY DEVELOP DURING
THE AFTERNOON AND CONTINUE INTO THE EVENING ACROSS THIS AREA...LACK
OF FAVORABLE INSTABILITY AND RELATIVELY WEAK DEEP-LAYER FLOW
SUGGESTS LITTLE SEVERE THREAT THROUGH THE END OF THE PERIOD.

.GOSS.. 04/17/2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 170601
SWODY2
SPC AC 170600

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE APR 17 2007

VALID 181200Z - 191200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
WEAKENING UPPER FEATURE -- MOVING ACROSS THE LOWER MS VALLEY LATE IN
THE DAY 1 PERIOD -- WILL CONTINUE TO WEAKEN WHILE BECOMING ABSORBED
INTO THE LARGER-SCALE CYCLONIC FLOW OVER THE OH VALLEY/MID-SOUTH
REGION. THIS FEATURE SHOULD MOVE OFF THE ATLANTIC COAST BY LATE
AFTERNOON...WHILE LARGER-SCALE CYCLONIC FLOW PERSISTS OVER THE ERN
CONUS.

FURTHER W...A COMPLEX UPPER TROUGH -- CONSISTING INITIALLY OF TWO
SEPARATE SHORT-WAVE TROUGHS/LOWS -- WILL EVOLVE OVER THE WRN CONUS.
THE ERN-MOST FEATURE SHOULD SHIFT ACROSS THE PAC NW/GREAT BASIN
THROUGH THE DAY...AND BEGIN AFFECTING THE NRN HIGH PLAINS BY LATE
AFTERNOON. THIS FEATURE WILL BE ACCOMPANIED BY A FAIRLY PRONOUNCED
SURFACE REFLECTION -- WHICH SHOULD RESIDE ACROSS THE HIGH PLAINS AS
A STRONG LEE LOW/TROUGH THROUGH THE LATTER HALF OF THE PERIOD.

..NRN HIGH PLAINS...
DRY BOUNDARY LAYER/VERY LOW PW WILL PREVAIL ACROSS THE NRN HIGH
PLAINS THIS PERIOD...AHEAD OF ADVANCING UPPER TROUGH. STEEP
MID-LEVEL LAPSE RATES AHEAD OF THIS TROUGH COMBINED WITH DAYTIME
HEATING SHOULD RESULT IN MARGINAL CAPE BY AFTERNOON...WITH A FEW
HIGH-BASED STORMS POSSIBLE. A STRONGER STORM OR TWO COULD PRODUCE
SMALL HAIL OR A LOCALLY STRONG WIND GUST. HOWEVER...IT APPEARS ATTM
THAT LIMITED INSTABILITY...AND SHEAR WHICH SHOULD REMAIN MARGINAL AT
BEST...WILL LIKELY PRECLUDE APPRECIABLE SEVERE THREAT.

.GOSS.. 04/17/2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 170540
SWODY1
SPC AC 170537

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1237 AM CDT TUE APR 17 2007

VALID 171200Z - 181200Z

..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
OVER SRN OK/NRN TX INTO THE ARKLATEX...

..SYNOPSIS...

AMPLIFIED YET PROGRESSIVE LARGE-SCALE PATTERN WILL CONTINUE THROUGH
THE DAY ONE PERIOD...WITH PRIMARY FEATURE OF INTEREST BEING MID AND
UPPER-LEVEL LOW WHICH WILL GRADUALLY WEAKEN AS IT TRANSLATES FROM
THE SRN HIGH PLAINS INTO THE CNTRL GULF COAST STATES BY WEDNESDAY
MORNING. IN THE LOW-LEVELS...ATTENDANT SURFACE LOW WILL DEVELOP
GENERALLY EWD FROM THE VICINITY OF THE TX/NM BORDER THROUGH N TX
INTO THE LOWER MS VALLEY BY THE END OF THE PERIOD.

..SRN OK/NRN TX INTO THE ARKLATEX...

17/00Z REGIONAL SOUNDINGS AND CURRENT GOES SOUNDER PW LOOP INDICATE
LOW LEVEL MOISTURE GRADUALLY INCREASING THROUGH SRN AND CNTRL TX
BENEATH A PRONOUNCED ELEVATED MIXED LAYER. LATEST SHORT TERM MODEL
GUIDANCE SUGGESTS THAT CAPPING/WARM MID LEVEL TEMPERATURES WILL
CONTINUE TO LIMIT INSTABILITY TODAY ACROSS CNTRL AND SRN TX DESPITE
A CONTINUED INCREASE IN BOUNDARY LAYER MOISTURE. THE GREATEST AIR
MASS DESTABILIZATION IS EXPECTED TO OCCUR INVOF SURFACE AND
MID-LEVEL LOWS OVER N TX WHERE MID-LEVEL COLD POOL WILL BE COLOCATED
WITH NWRN EDGE OF LOW-LEVEL MOISTURE AXIS /I.E. LOW TO MID 50
DEWPOINTS/...EFFECTIVELY CONTRIBUTING TO MLCAPES OF 500-1000
J/KG...MUCH OF WHICH WILL BE CONTAINED BELOW 500 MB.

TSTMS WILL BECOME INCREASINGLY LIKELY BY AFTERNOON INITIALLY OVER
THE TX PNHDL/W TX WITHIN STEEP LAPSE RATE AIR MASS...BUT W OF
PRIMARY LOW-LEVEL MOISTURE AXIS. SOME HAIL/LOCALLY GUSTY WINDS WILL
BE POSSIBLE WITH THESE STORMS. MORE VIGOROUS TSTM DEVELOPMENT IS
ANTICIPATED BY MID/LATE AFTERNOON AHEAD OF SURFACE LOW AND PERHAPS
SWD ALONG DRYLINE OVER N TX AS LARGE-SCALE FORCING FOR ASCENT
ASSOCIATED WITH MIGRATORY UPPER LOW ACTS ON DESTABILIZING WARM
SECTOR.

FORECAST SOUNDINGS WITHIN THIS AXIS OF STRONGER INSTABILITY INDICATE
RELATIVELY STRONG WIND FIELDS ABOVE 6-7 KM...NEAR AND ABOVE THE
ANTICIPATED EL HEIGHT. AS SUCH...MUCH OF THIS SHEAR WILL LIKELY NOT
BE REALIZED BY MATURE STORMS WITH EFFECTIVE BULK SHEARS IN THE 25-35
KT RANGE. THIS MODEST BULK SHEAR COUPLED WITH 0-3 KM SRH OF 100-150
M2/S2 INDICATE SOME POTENTIAL FOR LOW-TOPPED SUPERCELLULAR STORMS
WITH THE PRIMARY SEVERE THREAT BEING LARGE HAIL. A COUPLE OF
TORNADOES WILL BE POSSIBLE...ESPECIALLY WITH ANY STORMS NEAR THE SFC
AND 500 MB LOWS WHERE AMBIENT VERTICAL VORTICITY WILL BE LOCALLY
STRONGER.

THE WIND/HAIL THREAT WILL SHIFT EWD INTO THE ARKLATEX BY THIS
EVENING...WITH STORMS GRADUALLY WEAKENING LATER TONIGHT AS LOW-LEVEL
LAPSE RATES AND RESULTANT INSTABILITY DECREASE.

.MEAD/GRAMS.. 04/17/2007

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