SPC AC 081611
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1111 AM CDT FRI APR 08 2011
VALID 081630Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM OK/KS INTO PORTIONS OF THE
MID MS AND OH VALLEYS...AS WELL AS THE CENTRAL APPALACHIANS TO THE
WRN CAROLINAS...
...SYNOPSIS...
A STRONG UPPER TROUGH IS FORECAST TO DIG ACROSS CA TODAY...WHILE
WEAK UPPER RIDGING TAKES PLACE OVER MOST AREAS EAST OF THE ROCKIES.
DESPITE THE RIDGING ALOFT...RATHER STRONG WESTERLY MID LEVEL FLOW
AND INCREASING INSTABILITY WILL RESULT IN A RISK OF SEVERE
THUNDERSTORMS OVER SEVERAL AREAS TODAY.
AT THE SURFACE A FRONTAL BOUNDARY FROM NRN NC EXTENDS NWWD ACROSS
APPALACHIANS THRU WRN WV AND THEN WWD TO N OF OH RIVER...THEN WSWWD
ACROSS CENTRAL MO TO SWRN KS/OK BORDER. THIS BOUNDARY SEPARATES THE
LARGE WARM SECTOR TO THE S WHICH IS UNDERGOING DESTABILIZATION FROM
BOTH THE PRESENCE OF AN EML AND ADVECTION OF GULF MOISTURE...AND A
COOLER AIR MASS TO THE N.
...OH/TN VALLEYS TO WRN CAROLINAS...
RAPID DESTABILIZATION IS TAKING PLACE EWD ACROSS KY/TN TO S OF
FRONTAL BOUNDARY WITH DEWPOINTS RISING INTO THE MID 60S. STRONG
HEATING IS OCCURRING THIS AM OVER LOWER OH VALLEY AND WILL LEAD TO A
MDTLY UNSTABLE...WEAKLY CAPPED AIR MASS BY EARLY THIS AFTERNOON.
MLCAPES AOA 2000 J/KG COUPLED WITH BRN SHEAR OF 50-60KT WILL
PROVIDE A FAVORABLE SEVERE THUNDERSTORM ENVIRONMENT PARTICULARLY FOR
LARGE HAIL GIVEN THE STEEP MID LEVEL LAPSE RATES.
STORMS SHOULD INITIATE VICINITY/S OF THE FRONTAL ZONE NEAR OH RIVER
BY EARLY/MID AFTERNOON AND THEN QUICKLY EVOLVE INTO LINE
SEGMENTS/BOWS AS WELL AS POSSIBLE SUPERCELLS. VERY LARGE HAIL WOULD
BE POSSIBLE ASSOCIATED WITH ANY SUPERCELL GIVEN THE EXPECTED
ENVIRONMENT ALONG WITH ISOLATED TORNADOES. HAVE INCREASED BOTH
WIND/HAIL PROBS WITH THE POTENTIAL FOR EVEN A HIGHER RISK OF WIND IF
STORMS EVOLVE INTO LINE SEGMENTS AND BOWS. ADDITIONALLY HAVE SPREAD
THE SLIGHT RISK INTO THE WESTERN CAROLINAS AS IT NOW APPEARS
SUFFICIENT INSTABILITY WILL BE PRESENT TO MAINTAIN AN ORGANIZED
THREAT GIVEN THE PRESENCE OF 40-50 KT OF SHEAR.
...OK/KS INTO MID MS AND OH VALLEYS THIS EVENING...
SURFACE BOUNDARY EXTENDING FROM NEAR THE OK/KS BORDER EASTWARD
INTO MO/IL WILL LIKELY BE FOCUS OF SEVERE THUNDERSTORM DEVELOPMENT.
OPERATIONAL AND EXPERIMENTAL MODEL
SOLUTIONS CONTINUE TO SUPPORT THE DEVELOPMENT OF ISOLATED
THUNDERSTORMS BY LATE THIS AFTERNOON OVER NORTHERN OK AND SOUTHEAST
KS DESPITE WEAK FORCING ALOFT. STRONG HEATING AND INCREASING
MOISTURE WILL HELP TO REDUCE CAP AND AID IN INITIATION. WITH
MLCAPES RISING TO 3000 J/KG SUPERCELL STORMS WILL BE LIKELY WITH
LARGE HAIL AND DAMAGING WINDS POSSIBLE. THE ACTIVITY IS EXPECTED TO
INCREASE IN COVERAGE AS IT SPREADS EASTWARD ALONG THE BOUNDARY INTO
THE MID MS VALLEY...AND EVENTUALLY INTO THE OH VALLEY AFTER
MIDNIGHT. DAMAGING WINDS WILL LIKELY BE THE MAIN THREAT...ALTHOUGH
LARGE HAIL WILL REMAIN POSSIBLE. IF SUPERCELL STRUCTURES CAN BE
SUSTAINED IT WILL INCREASE THE POTENTIAL FOR TORNADOES AND VERY
LARGE HAIL. EXPECTED COVERAGE PRECLUDES THE INCREASING LOWER RISK
COVERAGE PROBABILITIES ATTM.
...GULF COAST STATES...
AMPLE LOW LEVEL MOISTURE HAS RETURNED TO THE GULF COAST REGION THIS
MORNING WITH MID/UPR 60 DEWPOINTS AS FAR NORTH AS TN.
WIDESPREAD LOW CLOUDS ARE RETARDING THE HEATING THIS MORNING.
HOWEVER...CINH WILL DECREASE SUFFICIENTLY THIS AFTERNOON COUPLED
WITH TRAILING ASCENT FROM SHORTWAVE TROUGH MOVING ACROSS TN AND MAY
RESULT IN A FEW STRONG TO SEVERE STORMS GIVEN THE EXPECTED LARGE
CAPE/MARGINAL SHEAR ENVIRONMENT.
..HALES/STOPPKOTTE.. 04/08/2011
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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