SWOMCD
SPC MCD 221535
PAZ000-MDZ000-VAZ000-DCZ000-WVZ000-221600-
MESOSCALE DISCUSSION 1074
NWS STORM PREDICTION CENTER NORMAN OK
1035 AM CDT TUE JUN 22 2010
AREAS AFFECTED...WRN/CENTRAL PA...MD...PARTS OF ERN WV...NRN/ERN VA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 221535Z - 221600Z
WW IS BEING CONSIDERED FOR PARTS OF WRN/CENTRAL PA SWD THROUGH
MD...PARTS OF ERN WV AND NRN/ERN VA.
SHORTWAVE TROUGH...CURRENTLY TRACKING EWD INTO THE LOWER GREAT
LAKES/UPPER OH VALLEY PER WATER VAPOR IMAGERY...WILL MOVE EWD INTO
NY/PA AND NRN VA/MD THIS AFTERNOON. 12Z UPPER AIR DATA INDICATED 40
KT WLY MIDLEVEL FLOW WITHIN THE BASE OF THIS TROUGH OVER OH.
OBJECTIVE ANALYSES SHOWED EFFECTIVE BULK SHEAR ALREADY INCREASING
ACROSS CENTRAL PA TO NRN VA AS THE STRONGER FLOW ALOFT SPREADS EWD.
IN THE LOW LEVELS...SURFACE FRONT ATTENDANT TO THE SHORTWAVE TROUGH
EXTENDED SSWWD FROM SWRN ONTARIO THROUGH CENTRAL OH. THIS BOUNDARY
WILL CONTINUE EWD TODAY AND MARK THE WRN EXTENT OF THE SEVERE
WEATHER THREAT.
CLOUDINESS/FILTERED SUNSHINE ACROSS PA...ASSOCIATED WITH CIRRUS AND
LEADING BAND OF ONGOING CONVECTION OVER CENTRAL PA TO THE ERN WV
PANHANDLE IS LIMITING SURFACE HEATING SOME THIS MORNING. THIS
COMBINED WITH WEAK MIDLEVEL LAPSE RATES APPEARS TO BE RESULTING IN A
SLOWER DESTABILIZATION OF THE AIR MASS THUS FAR. HOWEVER... FURTHER
DIABATIC HEATING WITHIN A MOIST AIR MASS IS EXPECTED TO SUPPORT AT
LEAST MODERATE INSTABILITY BY THIS AFTERNOON WITH MLCAPE 1000-1500
J/KG EXTENDING FROM OH INTO CENTRAL PA AND SWD TO VA/MD.
12Z WRF-HRRR SUGGESTED THE ONGOING STORMS OVER CENTRAL PA TO ERN WV
PANHANDLE WILL CONTINUE TO WEAKEN...WITH NEW TSTMS DEVELOPING OVER
WRN PA TO WV AROUND 17Z AS THE FRONT MOVES EWD. MODERATE
INSTABILITY AND EFFECTIVE BULK SHEAR UP TO 40 KT WILL SUPPORT
ORGANIZED STORMS WITH A THREAT OF HAIL...STRONG WIND GUSTS AND A
POTENTIAL TORNADO THREAT. THE TORNADO THREAT WILL BE GREATER IN ANY
LOCATION WHERE LOW LEVEL WINDS ARE MORE SLY...HENCE INCREASING LOW
LEVEL DIRECTIONAL SHEAR. GREATEST TORNADO THREAT SHOULD BE EAST OF
THE MOUNTAINS. HOWEVER...FORECAST SOUNDINGS SUGGEST SURFACE WINDS
AHEAD OF THE FRONT IN WRN PA WILL REMAIN FAVORABLY BACKED TO SUPPORT
A TORNADO THREAT WITH INITIAL ACTIVITY PRIOR TO WINDS VEERING WITH
FRONTAL PASSAGE.
..PETERS.. 06/22/2010
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PHI...BGM...AKQ...CTP...LWX...PBZ...RLX...
LAT...LON 38187937 38788034 40157970 41467932 41977857 41977692
41967597 41317563 40447576 39717614 38687671 38057714
38187937
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