MESOSCALE DISCUSSION 0778 NWS STORM PREDICTION CENTER NORMAN OK 1052 AM CDT SAT MAY 09 2009 AREAS AFFECTED...MUCH OF NY THROUGH SRN AND CNTRL VT CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 091552Z - 091715Z STORMS ARE EXPECTED TO DEVELOP EWD THROUGH NY AND EVENTUALLY INTO VT THIS AFTERNOON. LARGE HAIL...DAMAGING WIND AND ISOLATED TORNADOES WILL BE POSSIBLE. WW WILL LIKELY BE NEEDED BEFORE 17Z. AT MID-DAY A COLD FRONT EXTENDS FROM A SURFACE LOW IN SRN ONTARIO SWWD THROUGH THE OH VALLEY. THE LOW SHOULD DEVELOP EAST INTO NY THIS AFTERNOON WITHIN ZONE OF DPVA AND ASCENT DOWNSTREAM FROM EWD MOVING SHORTWAVE TROUGH OVER THE GREAT LAKES. AXIS OF UPPER 50S DEWPOINTS HAS SPREAD THROUGH PRE-FRONTAL WARM SECTOR. WIDESPREAD CLOUDS ARE SLOWING DIABATIC HEATING SOMEWHAT...BUT SUFFICIENT BREAKS EXIST TO BOOST TEMPERATURES INTO THE MID 70S BY EARLY AFTERNOON. SOMEWHAT LIMITED LOW LEVEL MOISTURE AND MODEST MID LEVEL LAPSE RATES WILL LIMIT MLCAPE TO AOB 1000 J/KG. STORMS CURRENTLY DEVELOPING OVER LAKE ERIE AND LAKE ONTARIO COULD BEGIN TO AFFECT NWRN PORTIONS OF NY BY 16Z. ADDITIONAL STORMS ARE LIKELY TO DEVELOP FARTHER EAST AS THE BOUNDARY LAYER DESTABILIZES. AN 80+ KT UPPER JET MAX ATTENDING THE GREAT LAKES IMPULSE WILL ADVANCE EWD INTO THE NERN STATES THIS AFTERNOON ACCOMPANIED BY A SWLY 30 KT LOW LEVEL JET. BULK SHEAR OF 50+ KT AND 150-250 M2/S2 WILL SUPPORT SUPERCELLS AND BOWING SEGMENTS. ..DIAL.. 05/09/2009 ATTN...WFO...BTV...ALY...BGM...BUF... LAT...LON 44117297 42947261 42287431 42137828 42837847 43257666 44437523 44117297 MESOSCALE DISCUSSION 0781 NWS STORM PREDICTION CENTER NORMAN OK 0156 PM CDT SAT MAY 09 2009 AREAS AFFECTED...NY THROUGH PORTIONS OF NEW ENGLAND CONCERNING...SEVERE THUNDERSTORM WATCH 280... VALID 091856Z - 092030Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 280 CONTINUES. ERN PORTIONS OF SEVERE THUNDERSTORM WATCH 280 MIGHT NEED TO BE REPLACED BY A TORNADO WATCH. OTHERWISE LARGE HAIL AND DAMAGING WIND WILL REMAIN LIKELY WITH THE STRONGER STORMS THIS AFTERNOON. STORMS HAVE INCREASED IN COVERAGE AND INTENSITY ACROSS SWRN THROUGH NRN NY AS ZONE OF DEEP ASCENT ATTENDING A PROGRESSIVE SHORTWAVE TROUGH MOVES EWD ABOVE A DESTABILIZING BOUNDARY LAYER. SURFACE ANALYSIS SHOWS LOW LEVEL WINDS HAVE REMAINED BACKED TO A MORE SLY OR SSWLY DIRECTION OVER ERN NY WITHIN ZONE OF PRESSURE FALLS EAST OF SURFACE LOW CURRENTLY OVER LAKE ERIE. THE LOW LEVEL JET IS FORECAST TO SHIFT NEWD THROUGH ERN NY AND SRN NEW ENGLAND AND THIS WILL LIKELY INCREASE THE SIZE OF THE LOW LEVEL HODOGRAPHS. IN ADDITION...VISIBLE IMAGERY SHOWS AN E-W ORIENTED OUTFLOW BOUNDARY FROM NRN NY INTO NRN VT WHICH COULD FURTHER AUGMENT TORNADO POTENTIAL WITH ANY SUPERCELL THAT MOVES ALONG THIS FEATURE. ..DIAL.. 05/09/2009 ATTN...WFO...GYX...BOX...BTV...ALY...BGM... LAT...LON 43377196 42407336 41827472 42617579 44747326 44517157 43377196