SWODY1
SPC AC 151612
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1112 AM CDT SAT MAY 15 2010
VALID 151630Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM LWR MS VALLEY EWD ACROSS
TN VALLEY AND SRN APPALACHIANS...
...THERE IS A SLGT RISK OF SVR TSTMS SRN PLAINS/LWR RIO GRANDE
VALLEY...
AS STRONG UPPER SYSTEM EXITS NERN U.S....THE LARGE SCALE FLOW
PATTERN BECOMES CONSIDERABLY WEAKER ACROSS THE CONUS. WEAK UPPER
LOW AND ASSOCIATED TROUGH CENTRAL ROCKIES MOVES EWD INTO CENTRAL/SRN
HIGH PLAINS THIS EVENING WHILE DOWNSTREAM RIDGING SHIFTS EWD TO
APPALACHIANS. A COUPLE MCV/S HAVE DEVELOPED OUT OF OVERNIGHT MCS
ACTIVITY. ONE DRIFTING ENEWD CURRENTLY CENTRAL LA WITH ANOTHER
UPSTREAM MOVING EWD TO OFFSHORE CENTRAL TX COAST THIS AFTERNOON.
AT THE SURFACE COLD FRONT HAS PUSHED SEWD TO VICINITY NC/VA BORDER
TRAILING WWD JUST S OF TN/KY BORDER. W OF MS RIVER THE EFFECTIVE
BOUNDARY HAS BEEN PUSHED SWD BY FRI CONVECTIVE ACTIVITY SRN PLAINS
SUCH THAT THE RICHER GULF AIR MASS IS CONFINED TO LOWER MS VALLEY
AND EXTREME S TX.
...LOWER MS VALLEY...
WITH THE ASCENT JUST AHEAD OF THE MCV CENTRAL LA...COUPLED WITH GOOD
HEATING ONGOING OF THE ALREADY MDTLY MOIST/UNSTABLE AIR MASS E OF MS
RIVER...HAVE EXTENDED THE SLGT RISK SWD THRU MS THIS
AFTERNOON...PRIMARILY FOR QUASI-ORGANIZED THUNDERSTORMS NOW MOVING
INTO SWRN MS. WHILE LAPSE RATES ARE GENERALLY LESS THAN
7C/KM...MLCAPES CLIMBING TO AOA 2000 J/KG AND 30KT OF LOW/MID LEVEL
SHEAR WILL BE SUFFICIENT FOR A FEW SEVERE THUNDERSTORMS BY MID
AFTERNOON...WITH HAIL AND LOCALLY DAMAGING DOWNBURSTS PRIMARY
THREAT.
...TN VALLEY EWD ACROSS SRN APPALACHIANS...
MINIMAL CLOUD COVER TO RETARD HEATING EITHER SIDE OF STALLING
FRONTAL ZONE WHICH WILL ALLOW MUCAPES TO CLIMB TO 2000 J/KG. WITH
THE RELAXATION OF THE UPPER FLOW SINCE FRI ACROSS THE FRONTAL ZONE
BOTH THE SHEAR AND LAPSE RATES WILL BE WEAKER. HOWEVER GIVEN THE
AVAILABLE INSTABILITY COUPLED WITH AROUND 30KT OF DEEP LAYER
SHEAR...SCATTERED STRONG/SEVERE THUNDERSTORMS EXPECTED AGAIN BY MID
AFTERNOON VICINITY FRONTAL ZONE FROM TN VALLEY EWD ACROSS SRN
APPALACHIANS TO AT LEAST CENTRAL NC.
...SWRN TX...
COMBINATION OF COLD FRONT AND OVERNIGHT CONVECTION HAS PUSHED
COOLER/STABLE BOUNDARY LAYER AIR MASS S AND W THRU MUCH OF SWRN TX.
WITH HEATING AND APPROACH OF MID LEVEL IMPULSE NOW OVER SRN
NM...EXPECT SUFFICIENT RECOVERY EWD TO CONTINUE THE THREAT OF A FEW
STRONG/SEVERE THUNDERSTORMS OVER SWRN TX MUCH AS DESCRIBED IN THE
13Z OUTLOOK. GIVEN THE INITIAL EXTENSIVE LOW CLOUDS...THE PRIMARY
THREAT PERIOD WILL LIKELY BE DELAYED UNTIL LATER THIS AFTERNOON AND
EVENING. A FAVORABLE EML WITH LAPSE RATES IN EXCESS OF 7C/KM
REMAIN AVAILABLE ACROSS SRN HI PLAINS...SO THAT ONCE SURFACE BASED
STORMS ARE ABLE TO FORM LATER THIS AFTERNOON...LARGE HAIL WILL AGAIN
BE A THREAT. SHEAR PROFILES WILL REMAIN MARGINAL BUT ISOLATED
SUPERCELLS WILL BE POSSIBLE PARTICULARLY ACROSS THE TRANS-PECOS
REGION.
..HALES/BOTHWELL.. 05/15/2010
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