SWODY1
SPC AC 011229
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0729 AM CDT TUE MAY 01 2007
VALID 011300Z - 021200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE SRN GREAT
LAKES ACROSS THE UPPER OH RIVER VALLEY...
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF CENTRAL TX...
..SRN GREAT LAKES INTO PA...
SURFACE LOW NEAR LSE EARLY THIS MORNING IS FORECAST TO DEVELOP EWD
ACROSS FAR SRN MI ALONG SURFACE WARM FRONT EXPECTED TO LIFT NWD NEAR
THE MI-IN/OH BORDER DURING THE AFTERNOON. THIS WILL OCCUR IN
RESPONSE TO FAST MOVING SHORTWAVE TROUGH WHICH WILL SHIFT EWD ACROSS
THE NRN GREAT LAKES TODAY. SRN PERIPHERY OF STRONG WNWLY FLOW ALOFT
ACCOMPANYING THIS WAVE WILL EXTEND OVER THE WARM SECTOR FROM NERN
IND INTO WRN PA WITH H5 WINDS FROM 40-50 KT. THIS WILL OCCUR IN
CONCURRENCE WITH STRENGTHENING WSWLY LLJ INTO ERN OH/WRN PA/SWRN NY
BY LATE TODAY AS H85 WINDS INCREASE AOA 25 KT. THUS...OVERALL SHEAR
WILL BECOME QUITE STRONG BY THE MID TO LATE AFTERNOON. THE STRONG
SHEAR WILL PERSIST ACROSS MUCH OF PA AFTER DARK AS LLJ AND SURFACE
WAVE MOVE QUICKLY ESEWD OFF THE MID ATLANTIC COAST BY THE END OF THE
PERIOD. PRIMARY CONCERN FOR SEVERE THUNDERSTORMS WILL THEREFORE
CENTER AROUND QUALITY OF LOW LEVEL MOISTURE AND ITS SUBSEQUENT
INFLUENCES ON INSTABILITY. APPEARS 10+C H85 DEW POINTS WILL ADVECT
STEADILY ENEWD AWAY FROM THE MID MS RIVER VALLEY AND EXTEND INTO THE
SRN GREAT LAKES EARLY TODAY. RESULTANT DOWNWARD MIXING WILL AID
ENEWD ADVECTION OF SURFACE MOISTURE AND ALLOW SURFACE DEW POINTS TO
INCREASE INTO MID/UPPER 50S BY THE EARLY AFTERNOON INTO WRN PA BY
LATE THIS AFTERNOON. GIVEN STEEP LAPSE RATES AND ABUNDANT SURFACE
HEATING...MLCAPE FROM 1000-1500 J/KG SHOULD BE QUITE COMMON WITHIN
WARM SECTOR OVER THIS AREA TODAY.
DEEP ASCENT...COLOCATED WITH STRENGTHENING SURFACE CONVERGENCE...
SHOULD SUPPORT SCATTERED TO NUMEROUS THUNDERSTORMS FROM PORTIONS OF
CENTRAL/NRN IL ACROSS THE SRN GREAT LAKES REGION BY THE MID TO LATE
AFTERNOON. SHEAR WILL BE MORE THAN ADEQUATE FOR SUPERCELLS AND
SMALL LINES/BOW ECHOES ACROSS THIS REGION. DAMAGING WINDS AND LARGE
HAIL SHOULD BE PRIMARY THREATS...THOUGH LOW LEVEL SHEAR WILL BE
FAVORABLE FOR A FEW TORNADOES ESPECIALLY NEAR H85-H7 JETS INTO NERN
OH/WRN PA. ACTIVITY WILL LIKELY BECOME MOST CONCENTRATED NEAR THE
LLJ AXIS INTO WRN/CENTRAL PA BY THIS EVENING...WITH STORMS BECOMING
INCREASINGLY ELEVATED NORTH AND EAST OF WARM FRONT INTO NY AND THE
MID ATLANTIC AFTER DARK.
..TX...
SEVERE THUNDERSTORM THREAT WILL BE RATHER NONDESCRIPT OVER TX TODAY
AS SLOW MOVING UPPER LOW BEGINS TO LOSE AMPLITUDE AS IT SHIFTS ENEWD
ACROSS OK THROUGH THE PERIOD. SURFACE FEATURES ACROSS CENTRAL TX
HAVE BECOME MUDDLED BY SEVERAL ROUNDS OF CONVECTION OVER THE PAST
FEW DAYS...INCLUDING ONGOING MCS EARLY THIS MORNING. PRIMARY
SURFACE WARM FRONT/REINFORCED OUTFLOW BOUNDARY EXTENDING ROUGHLY E-W
ACROSS CENTRAL TX FROM NEAR UTS/CLL TO NORTH OF AUS TO BETWEEN SJT
AND JCT MAY PERSIST FOR MUCH OF THE DAY. THIS FEATURE WILL EXIST
ALONG NRN EDGE OF RICH GULF MOISTURE ACROSS SOUTH TX. THOUGH DEEP
ASCENT WILL REMAIN MOSTLY ABSENT...CONVERGENCE AND LIKELY
DEVELOPMENT OF MODERATE TO STRONG INSTABILITY NEAR SURFACE
BOUNDARIES MAY SUPPORT REDEVELOPMENT OF STRONG TO SEVERE STORMS OVER
CENTRAL TX TODAY. WLY FLOW ALOFT WILL WEAKEN...THOUGH MID LEVEL
WINDS SHOULD STILL REMAIN AROUND 30 KT...AND SUPPORT SUFFICIENT
SHEAR FOR ORGANIZED LINES AND ISOLATED SUPERCELLS.
.EVANS/GRAMS.. 05/01/2007
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