SPC MESOSCALE DISCUSSION 1461 FOR NEW ENGLAND AND ERN NY
CONCERNING...SEVERE THUNDERSTORM POTENTIAL... 

VALID 101550Z - 101800Z 

ONGOING CONVECTION PER REGIONAL RADARS IS EXPECTED TO INCREASE IN
INTENSITY/AREAL COVERAGE DURING THE NEXT 1-2 HOURS FROM ERN NY TO SWRN
MAINE.  WW MAY BE REQUIRED WITHIN THE NEXT HOUR. 

AIRMASS OVER ERN NY INTO NEW ENGLAND HAS DESTABILIZED THIS MORNING WITH
MLCAPE VALUES FROM NERN NY TO SWRN MAINE RANGING FROM 1000- 1500 J/KG.
MID-LEVEL WINDS ARE QUITE STRONG PER MORNING UA ANALYSIS WITH 700-500 MB
WLY FLOW AT 40-50 KT.  LARGE SCALE LIFT AHEAD OF UPPER SHORTWAVE TROUGH
OVER SRN QUEBEC WILL AID IN UPDRAFT STRENGTH INTO THE AFTERNOON OVER NEW
ENGLAND.  THE STRONG WLY UPPER LEVEL FLOW COMBINED WITH DRYING IN THE
MID-LEVELS MOVING INTO NRN NY PER WATER VAPOR IMAGERY WILL ENHANCE THE
DOWNDRAFT POTENTIAL. IN ADDITION...LOW WET-BULB ZERO HEIGHTS AROUND 9
KFT WILL ALSO SUPPORT LARGE HAIL WITH THE STRONGEST STORMS. 

..PETERS.. 07/10/01



SPC MESOSCALE DISCUSSION 1462 FOR ERN PA/NJ/DE/MD/NRN VA/DC
CONCERNING...SEVERE THUNDERSTORM POTENTIAL... 

VALID 101658Z - 102000Z 

THUNDERSTORMS SHOULD CONTINUE TO INCREASE IN INTENSITY/AREAL COVERAGE
THIS AFTERNOON FROM ERN PA TO NRN VA AND THEN TRACK ESEWD TO NJ/DE/ERN
MD.  STRONG WINDS AND LARGE HAIL WILL BE THE PRIMARY THREAT.  WW MAY BE
ISSUED DURING THE NEXT 1-3 HOURS. 

VISIBLE SATELLITE IMAGERY SHOWS TOWERING CU DEVELOPING OVER THE
APPALACHIAN MOUNTAINS FROM WV NNEWD INTO CENTRAL PA WHERE THE AIRMASS
HAS CONTINUED TO DESTABILIZE WITH MLCAPE VALUES UP TO 1000- 1500 J/KG.
CLEAR SKIES DOWNSTREAM INTO NRN VA/MD/DE/NJ/ERN PA HAVE ALLOWED SURFACE
TEMPERATURES TO RISE INTO THE UPPER 80S TO LOWER 90S WITH SURFACE
DEWPOINTS RANGING FROM THE MIDDLE 60S TO AROUND 
70.  THIS AREA SHOULD CONTINUE TO DESTABILIZE THIS AFTERNOON WITH
ADDITIONAL HEATING.  WNWLY MID-UPPER LEVEL FLOW AT 35-40 KT COMBINED
WITH MID-LEVEL DRYING FROM NERN OH TO MD/PA/SRN NJ SHOULD ENHANCE THE
POTENTIAL FOR STRONG DOWNDRAFTS.  FURTHER DESTABILIZATION OVER THE AREA
OF CONCERN THIS AFTERNOON WILL ALLOW ANY STORMS THAT DEVELOP OVER THE
APPALACHIANS TO TRACK SEWD WITHIN THE WNWLY UPPER FLOW.  DAMAGING WINDS
ARE LIKELY WITH THE STRONGER ACTIVITY. 

..PETERS.. 07/10/01



SPC MESOSCALE DISCUSSION 1463 FOR CENTRAL AND ERN NY INTO NEW ENGLAND
CONCERNING...SEVERE THUNDERSTORM WATCH 537... 

VALID 101759Z - 102000Z 

A LINE OF STRONG/SEVERE STORMS OVER NRN NH INTO WRN MAINE IS TRACKING TO
THE ENE AT 20-30 KT.  THIS ACTIVITY IS EXPECTED TO MOVE EAST OF WW 537
DURING THE NEXT HALF HOUR.  HOWEVER...AREAL EXTENT OF SEVERE THREAT EAST
OF CURRENT WW IS TOO SMALL TO WARRANT AN ADDITIONAL WW.  A WW MAY BE
REQUIRED SOUTH OF WW 537...IF ACTIVITY DEVELOPS SWD. 

STRONG MID-UPPER LEVEL FLOW FROM NRN/ERN NY INTO NEW ENGLAND WITH BTV
VAD WINDS SHOWING WLY 500 MB WINDS AT 40-50 KT CONTINUE TO SUPPORT
ORGANIZED STORMS WITHIN WW 537.  AIRMASS REMAINS MODERATELY UNSTABLE
WITH MLCAPE VALUES RANGING FROM 1000-1500 J/KG.  DAMAGING WINDS SHOULD
BE THE PRIMARY SEVERE THREAT THROUGH THE AFTERNOON. THE DEGREE OF
INSTABILITY COMBINED WITH THE STRONG UNIDIRECTIONAL FLOW OVER THIS
REGION WILL SUPPORT ADDITIONAL ORGANIZED STORMS. A NEW WW MAY BE NEEDED
OVER SERN NY INTO SRN NEW ENGLAND. 

..PETERS.. 07/10/01



SPC MESOSCALE DISCUSSION 1464 FOR...IND/OH SWRN PA/WV AND MD...
CONCERNING...SEVERE THUNDERSTORM POTENTIAL... 

VALID 101931Z - 102300Z 

A SEVERE THUNDERSTORM WATCH WILL LIKELY BE ISSUED FOR PARTS OF THE ABOVE
AREAS FOR LATE THIS AFTERNOON AND INTO THE EVENING. 

INSTABILITY AND CONVERGENCE HAVE BEEN INCREASING ALONG PREFRONTAL TROUGH
ACROSS NRN IN AND OH. LATEST RADAR LOOPS INDICATE STORMS HAVE INITIATED
OVER DEKALB COUNTY IN NERN IND...AND OVER DEFIANCE AND PAULDING COUNTIES
OF NWRN OH. STRONG HEATING AHEAD OF THIS ACTIVITY WILL LIKELY RESULT IN
THE DEVELOPMENT OF GREATER INSTABILITY WHICH SHOULD SUSTAIN TSTMS AS UPR
TROUGH AND COLD FRONT MOVE INTO THE REGION LATER TODAY. DEEP LAYER SHEAR
OF 40-50 KT... BASED ON VWP AND 18Z DTX SOUNDING...WILL AID STORM
ORGANIZATION WITH AN INCREASING THREAT OF HAIL AND DAMAGING WINDS. 

..CARBIN.. 07/10/01