SPC AC 122221
DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
0521 PM CDT WED MAY 12 2010
VALID 122215Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN KS/MO AND VICINITY
SSWWD INTO PARTS OF W CENTRAL TX...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS VA AND VICINITY...
AMENDED FOR ADJUSTMENT OF SLIGHT RISKS IN TX PNHDL/S PLAINS AND THE
MID-ATLANTIC
.UPDATE DISCUSSION... /ISSUED 0515 PM CDT WED MAY 12 2010/
...TX PNHDL/S PLAINS...
PRESSURE FALLS OVER THE HIGH PLAINS HAVE CAUSED LLVL SELY BOUNDARY
LAYER FLOW TO INCREASE OVER THE TX PNHDL/S PLAINS. DRYLINE HAS
CONTINUED TO RETREAT TO THE S OF A CDFNT WITH TSTMS DEVELOPING
FARTHER W THAN EARLY ANTICIPATED. /JPR
.PREV DISCUSSION... /ISSUED 0258 PM CDT WED MAY 12 2010/
...CENTRAL AND SRN PLAINS...
ELEVATED CONVECTION -- AND A LOW-END HAIL THREAT -- CONTINUES FROM
PORTIONS OF CENTRAL IA SSWWD INTO NWRN MO/NERN KS. MEANWHILE...
SURFACE-BASED DEVELOPMENT IS BEGINNING TO OCCUR FROM S CENTRAL KS --
INVOF THE SURFACE COLD FRONT -- SSWWD INTO W CENTRAL TX ALONG THE
DRYLINE. SHEAR QUITE FAVORABLE FOR SUPERCELLS COUPLED WITH
MIXED-LAYER CAPE NOW IN THE 3000 TO 4000 J/KG RANGE AHEAD OF THE
FRONT/DRYLINE SUGGEST THAT SEVERE POTENTIAL WILL CONTINUE TO
INCREASE THIS AFTERNOON AND EVENING IN CONJUNCTION WITH FURTHER CAP
EROSION/STORM DEVELOPMENT.
WHILE LOW-LEVEL SHEAR REMAINS SOMEWHAT WEAK...ISOLATED/CELLULAR
STORM MODE...A MOIST BOUNDARY LAYER...AND FAVORABLE DEEPER-LAYER
SHEAR WILL SUPPORT A THREAT FOR ISOLATED TORNADOES...WHILE
LOCALLY-DAMAGING WINDS WILL ALSO BE POSSIBLE WITH STRONGER CELLS.
HOWEVER...PRIMARY SEVERE POTENTIAL REMAINS VERY LARGE HAIL...WITH
THE THREAT LIKELY TO CONTINUE THROUGH THIS EVENING AND PERHAPS
OVERNIGHT AS CONVECTION SPREADS EWD/NEWD ACROSS N CENTRAL
TX...OK...ERN KS...AND NRN AND WRN MO.
...WV/VA AND VICINITY...
MCS CONTINUES SPREADING SEWD ACROSS WRN AND CENTRAL VA ATTM...WITH
NEW STORMS FORMING OVER PARTS OF NERN KY AND VICINITY IN THE WAKE OF
THE EARLIER CONVECTION. WITH 1500 TO 2000 J/KG MIXED-LAYER CAPE NOW
INDICATED E OF THE MOUNTAINS AND WLY MID-LEVEL FLOW NEAR 50 KT
PROVIDING FAVORABLE SHEAR...THREAT FOR DAMAGING WINDS AND/OR HAIL
SHOULD CONTINUE/SPREAD EWD ACROSS VA THROUGH THE AFTERNOON AND INTO
THIS EVENING BEFORE DIMINISHING. /GOSS
..JPR/GOSS.. 05/12/2010
.PREV DISCUSSION... /ISSUED 1129 AM CDT WED MAY 12 2010/
...CENTRAL/SOUTHERN PLAINS...
A LARGE UPPER TROUGH REMAINS OVER THE WESTERN STATES TODAY...WITH
BAND OF 70-90 KNOT MID LEVEL WINDS EXTENDING FROM AZ/NM INTO THE
CENTRAL PLAINS. THE MAIN SURFACE BAROCLINIC ZONE LIES FROM CENTRAL
MO INTO SOUTH CENTRAL KS WHERE A WEAK SURFACE LOW IS EVIDENT. THIS
BOUNDARY WILL PROVIDE THE PRIMARY FOCUS FOR STRONG/SEVERE
THUNDERSTORM DEVELOPMENT LATER TODAY AND TONIGHT. 12Z RAOBS IN THE
WARM SECTOR SUGGEST THAT THE STRONG CAP WILL INHIBIT DEEP CONVECTION
AWAY FROM THE BOUNDARY THROUGH MOST OF THE DAY.
HOWEVER...INCREASING LOW LEVEL WARM ADVECTION AND LIFT ASSOCIATED
WITH WEAK SHORTWAVE TROUGH OVER EASTERN NM/WEST TX MAY EVENTUALLY
ERODE THE CAP OVER NORTHERN OK/SOUTHERN KS. THIS WILL LEAD TO
SCATTERED SEVERE STORMS ALONG THE FRONT...AND THE POTENTIAL FOR AT
LEAST ISOLATED CELLS FORMING DISCRETELY IN THE WARM SECTOR.
THERMODYNAMIC PROFILES IN THIS AREA WILL BE VERY UNSTABLE WITH
DEWPOINTS NEAR 70F AND MLCAPE VALUES OF 3000-4000 J/KG. FORECAST
SOUNDINGS SUGGEST STRONG EFFECTIVE SHEAR /OVER 50 KNOTS/ WILL
SUPPORT SUPERCELL STORMS CAPABLE OF VERY LARGE HAIL AND DAMAGING
WINDS. ANY DISCRETE STORM THAT FORMS OFF THE FRONT WILL ALSO HAVE
SUFFICIENT LOW LEVEL VERTICAL SHEAR /ESPECIALLY AFTER 00Z/ FOR THE
THREAT OF A FEW TORNADOES. ACTIVITY SHOULD TRACK/DEVELOP
NORTHEASTWARD ACROSS SOUTH CENTRAL KS AND INTO WESTERN MO THROUGH
THE EVENING WITH THE RISK OF RATHER WIDESPREAD HAIL.
FARTHER SOUTHWEST...IT APPEARS LIKELY AT LEAST ISOLATED
THUNDERSTORMS WILL DEVELOP ALONG THE SURFACE DRYLINE OVER WESTERN OK
AND WESTERN NORTH TX. THESE STORMS WILL TRACK EAST-NORTHEASTWARD
THIS EVENING AND WILL ALSO POSE A RISK OF LARGE HAIL AND DAMAGING
WINDS.
...KY/WV INTO VA...
A LARGE MCS IS ONGOING THIS MORNING OVER PARTS OF KY/WV. GIVEN THE
MESOSCALE ORGANIZATION OF THIS SYSTEM...IT APPEARS LIKELY TO
MAINTAIN ITS INTENSITY THROUGH THE DAY AS IT CROSSES THE
APPALACHIANS INTO VA. SUNNY SKIES AHEAD OF THE STORMS...COMBINED
WITH DEWPOINTS CLIMBING THROUGH THE 60S WILL PROVIDE SUFFICIENT
DESTABILIZATION FOR THE RISK OF SEVERE STORMS. DAMAGING WINDS
APPEAR TO BE THE MAIN THREAT.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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