SWOMCD
SPC MCD 101757
PAZ000-MDZ000-VAZ000-DCZ000-WVZ000-101930-
MESOSCALE DISCUSSION 1024
NWS STORM PREDICTION CENTER NORMAN OK
1257 PM CDT WED JUN 10 2009
AREAS AFFECTED...S-CENTRAL PA...MUCH OF MD...CENTRAL VA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 101757Z - 101930Z
AS THUNDERSTORM COVERAGE INCREASES DURING THE AFTERNOON FROM
S-CENTRAL PA SWD INTO MD AND VA...THE POTENTIAL FOR STRONG TO SEVERE
THUNDERSTORM DEVELOPMENT IS POSSIBLE. CONVECTIVE TRENDS WILL BE
MONITORED FOR A WW.
RADAR AND SATELLITE IMAGERY INDICATE A CLUSTER OF THUNDERSTORMS
MOVING E THROUGH THE OH VALLEY. THIS ACTIVITY IS OCCURRING
IMMEDIATELY AHEAD OF AN UPPER LEVEL IMPULSE EMBEDDED WITHIN
MODERATELY STRONG ZONAL FLOW ALOFT. AT THE SURFACE...A QUASI
STATIONARY FRONTAL BOUNDARY WAS LOCATED ACROSS CENTRAL
PA...EXTENDING SW THROUGH THE OH VALLEY TOWARD A WEAK SURFACE LOW
OVER SRN IL. A ZONE OF SURFACE CONVERGENCE WAS ALSO OBSERVED
EXTENDING SWD FROM ERN PA INTO S-CENTRAL/SWRN VA...WHERE AN AGITATED
CUMULUS FIELD WAS BEGINNING TO DEVELOP PER VIS SATELLITE IMAGERY.
SURFACE TEMPERATURES OVER THE ERN HALF OF PA INTO VA HAVE WARMED
INTO THE LOW TO MID 80S...AND SURFACE DEWPOINTS RESIDE IN THE MID TO
UPPER 60S. THOUGH MORNING RAOBS AND CURRENT RUC SOUNDINGS INDICATE
MID LEVEL LAPSE RATES ARE FAIRLY WEAK...FAVORABLE SURFACE HEATING
AND MOISTURE ARE CONTRIBUTING TOWARD 1500-2000 J/KG OF MLCAPE. THIS
ENVIRONMENT SHOULD SUPPORT THUNDERSTORM INITIATION DURING THE NEXT
FEW HOURS. IN ADDITION...ACTIVITY OVER OH/KY/WV SHOULD SPREAD E INTO
VA BY MID AFTERNOON...AND MAY INCREASE IN VIGOR AS THEY ENCOUNTER
LARGER INSTABILITY.
DEEP LAYER VERTICAL WIND SHEAR IS FORECAST TO BE STRONGEST OVER PA
/30-40 KT OF EFFECTIVE BULK SHEAR/ DUE TO CLOSER PROXIMITY TO
STRONGER WLY FLOW ALOFT...SUPPORTING ORGANIZED MULTICELL
THUNDERSTORMS AND PERHAPS BRIEF SUPERCELL STRUCTURES. FARTHER S OVER
VA...THE SEVERE THREAT WILL LIKELY BE MORE PULSE LIKE IN
NATURE...DRIVEN MAINLY BY FAVORABLE LOW LEVEL THERMODYNAMICS. THE
AREA WILL CONTINUE TO BE MONITORED FOR A LARGE HAIL/DAMAGING WIND
THREAT /AND POSSIBLE WW/ DURING THE NEXT FEW HOURS.
..GARNER.. 06/10/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...AKQ...CTP...LWX...RNK...
LAT...LON 39987626 38437668 36957761 36597879 36697974 37638009
39137921 40037859 40697771 40577691 39987626
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