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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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