SWODY1
SPC AC 261957
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT SAT APR 26 2008
VALID 262000Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF WEST/CENTRAL
TX...
...TX...
OVERALL SCENARIO FOR SEVERE THUNDERSTORM DEVELOPMENT REMAINS SIMILAR
TO EARLIER FORECASTS. AFTERNOON WATER VAPOR IMAGERY FEATURES COMPACT
SHORTWAVE TROUGH DIGGING ESEWD INTO THE CENTRAL HIGH PLAINS. AHEAD
OF THIS FEATURE...GRADUAL BOUNDARY LAYER MOISTURE RETURN IS
OCCURRING ACROSS PORTIONS OF WEST/CENTRAL TX...CHARACTERIZED BY
50-55 F DEWPOINTS INTO WEST CENTRAL TX AS OF 19Z...WITH LOWER 60S F
DEWPOINTS ACROSS THE CENTRAL TX HILL COUNTRY.
VISIBLE SATELLITE IMAGERY/FORECAST SOUNDINGS INDICATE STRONG
AFTERNOON HEATING WILL SUPPORT MODERATE INSTABILITY/WEAK CINH WITH
MLCAPE OF 1000-1500 J/KG ACROSS WEST/SOUTHWEST TX LATE THIS
AFTERNOON/EARLY EVENING PER LATEST RUC SOUNDINGS. ACCORDINGLY...A
SEVERE THREAT IS LIKELY TO DEVELOP OVER PORTIONS OF WEST TX BY LATE
AFTERNOON...WITH THESE STORMS SPREADING ESEWD AND INCREASING IN
COVERAGE DURING THE EVENING. DEEP LAYER SHEAR ON THE ORDER OF 40-50
KT WILL INITIALLY SUPPORT HIGH-BASED/LP-SUPERCELLS...WITH THE LIKELY
EVOLUTION OF ONE OR MORE SEVERE CLUSTERS/BOWING LINES DURING THE
EARLY EVENING HOURS. LARGE HAIL AND DAMAGING WINDS SHOULD BE THE
PRIMARY SEVERE RISKS...WITH ANY TORNADO THREAT LIMITED BY MODEST
BOUNDARY LAYER MOISTURE/HIGH LCLS AOA 2000 M.
...LA INTO THE SRN APPALACHIANS...
SLOW MOVING FRONT WILL REMAIN A FOCUS FOR ADDITIONAL SCATTERED
THUNDERSTORMS THROUGH EARLY EVENING. MODERATE TO STRONG INSTABILITY
AND 25-30 KT OF DEEP LAYER SHEAR WILL FAVOR SOME ISOLATED SEVERE
HAIL AND DAMAGING WINDS THROUGH AROUND SUNSET.
...APPALACHIANS INTO NY/PA...
REFERENCE MESOSCALE DISCUSSION 743 FOR SHORT TERM DETAILS.
INCREASING DEEP ASCENT IS EXPECTED TO OVERSPREAD WRN NY/PA AS SRN
FRINGE OF SYSTEM EJECTING OUT OF THE GREAT LAKES GLANCES THE
REGION...AND SURFACE COLD FRONT PUSHES EWD TODAY. OVERALL UPPER
LEVEL SETUP AND NARROW CORRIDOR OF MODERATE PRE-FRONTAL MOISTURE
FAVORS A FEW POCKETS OF STRONGER STORMS WITH ISOLATED MARGINALLY
SEVERE HAIL/LOCALLY DAMAGING WINDS. SEASONABLY STRONG HEATING
SHOULD SUPPORT HIGH-BASED STORMS AND VERY STEEP LOW LEVEL LAPSE
RATES INTO THE MID ATLANTIC REGION...WHICH COULD SUPPORT A FEW EWD
MOVING CLUSTERS WITH STRONG/ISOLATED DAMAGING WINDS INTO THE EARLY
EVENING.
...CENTRAL PLAINS...
LARGE SCALE ASCENT ASSOCIATED WITH HIGH PLAINS IMPULSE WILL INCREASE
ACROSS THE CENTRAL PLAINS THIS AFTERNOON/EVENING. LOW LEVEL MOISTURE
WILL BE QUITE MARGINAL /SURFACE DEWPOINTS IN THE 35-45 F IN
KS/...BUT STEEP LAPSE RATES COUPLED WITH SURFACE HEATING MAY FOSTER
DEVELOPMENT OF HIGH-BASED TSTMS ALONG EWD MOVING COLD FRONT. GIVEN
STEEP LOW LEVEL LAPSE RATES WITH WEAK INSTABILITY AND MUCAPE OF
200-400 J/KG...A FEW OF THESE STORMS COULD YIELD ISOLATED DAMAGING
WIND GUSTS/SOME HAIL THROUGH SUNSET.
..GUYER.. 04/26/2008
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