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MESOSCALE DISCUSSION 1603
NWS STORM PREDICTION CENTER NORMAN OK
1250 PM CDT THU JUL 26 2012

AREAS AFFECTED...PORTIONS SRN/CENTRAL/ERN NY...WRN NEW
ENGLAND...NERN PA.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 261750Z - 261945Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...BAND OF TSTMS INTENSIFYING OVER NRN PORTIONS WW 524...AND
MOVING EWD ABOUT 40 KT...WILL CONTINUE TO POSE SVR THREAT FARTHER E
ACROSS THIS AREA. ADDITIONAL DEVELOPMENT IS POSSIBLE ALONG AND EVEN
N OF WARM FRONT AS WELL. MAIN THREAT IS SVR GUSTS...THOUGH
SUPERCELLS WITH LARGE HAIL ALSO ARE POSSIBLE AND A TORNADO OR TWO
CANNOT BE RULED OUT.

DISCUSSION...17Z SFC MESOANALYSIS SHOWED WARM FRONT OVER
NWRN...CENTRAL AND SERN PA...BECOMING SOMEWHAT DIFFUSE IN THERMAL
FIELDS GIVEN STG SFC DIABATIC HEATING OCCURRING ON BOTH SIDES. IN
FACT...AIR MASS N OF WARM FRONT HAS BECOME MINIMALLY CAPPED...WITH
SFC DEW POINTS UPPER 60S AND TEMPS LOW 80S F CONTRIBUTING TO MLCAPE
IN 1000-1500 J/KG RANGE. THIS SHOULD INCREASE TO 2000-2500 J/KG
RANGE BEFORE ARRIVAL OF TSTM BAND. MLCINH WILL ERODE FROM W-E
ACROSS THIS CORRIDOR DUE TO COMBINATION OF DIABATIC HEATING AND
MOIST ADVECTION...RENDERING AREAS FROM HUDSON VALLEY INTO WRN NEW
ENGLAND FAVORABLY UNSTABLE PRIOR TO CONVECTIVE ARRIVAL...HOWEVER AIR
MASS WILL REMAIN MORE STABLE WITH EWD EXTENT FROM THERE. GIVEN
STRENGTH OF LOW-LEVEL SPEED SHEAR...HODOGRAPHS WILL REMAIN
RELATIVELY LARGE INVOF SFC WARM FRONT...DESPITE LACK OF APPRECIABLE
VEERING WITH HEIGHT. DEEP SHEAR WILL REMAIN FAVORABLE AS
WELL...WITH EFFECTIVE SHEAR MAGNITUDES 45-50 KT OVER MOST OF AREA.

..EDWARDS/HART.. 07/26/2012

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