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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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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