MESO: Mesoscale Discussion 0801

ACUS11 KWNS 181556
SWOMCD
SPC MCD 181555
VAZ000-MDZ000-PAZ000-DCZ000-WVZ000-OHZ000-181700-

MESOSCALE DISCUSSION 0801
NWS STORM PREDICTION CENTER NORMAN OK
1055 AM CDT WED MAY 18 2011

AREAS AFFECTED...PARTS OF CENTRAL AND NRN VA...CENTRAL AND WRN
MD...ERN AND NRN WV...SRN AND SWRN PA...AND SERN OH

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 181555Z - 181700Z

A WW MAY BE NEEDED FOR PARTS OF THE AREA FROM SERN OH/SWRN PA TO THE
CHESAPEAKE BAY/TIDEWATER AREA.

GIVEN THE POTENTIAL THREAT FOR ISOLATED TORNADO OR TWO AND A GREATER
THREAT FOR SEVERE HAIL THAN YESTERDAY...A SLIGHT RISK WILL BE ADDED
TO PARTS OF THIS AREA IN THE UPCOMING 1630Z DAY 1 CONVECTIVE
OUTLOOK.

AN INCREASE IN TSTM DEVELOPMENT IS EXPECTED INTO THE AFTERNOON
ACROSS MUCH OF CENTRAL AND NRN VA...CENTRAL AND WRN MD INCLUDING THE
CHESAPEAKE BAY AND TIDEWATER AREA...SRN AND SWRN PA...ERN AND NRN WV
AND SERN OH. DESPITE SOME CLOUDINESS...MORNING VISIBLE SATELLITE
IMAGERY SHOWED THE GREATEST SURFACE HEATING POTENTIAL ACROSS THE
DISCUSSION AREA. THIS COMBINED WITH SURFACE DEWPOINTS IN THE MID
50S TO AROUND 60 F AND MIDLEVEL LAPSE RATES 6.5-7 C/KM IS ALREADY
RESULTING IN MUCAPE TO AROUND 1000 J/KG. ADDITIONAL DESTABILIZATION
TODAY AND FORCING FOR ASCENT SPREADING NNWWD ATTENDANT TO A MIDLEVEL
SHORTWAVE TROUGH ROTATING NWD FROM SRN VA WILL AID IN FURTHER TSTM
DEVELOPMENT.

A FEW STORMS HAVE ALREADY SHOWN SIGNS OF LOW LEVEL ROTATION. GIVEN
EFFECTIVE BULK SHEAR 40-45 KT ACROSS THIS REGION TODAY...ORGANIZED
STORMS WILL BE POSSIBLE WITH STORM MODES BEING BOTH MULTICELLS AND
SUPERCELLS. OBJECTIVE ANALYSES SHOWED AN ENHANCED AREA OF AMBIENT
SURFACE VORTICITY OVER NRN VA/ERN WV PANHANDLE TO SWRN PA/SERN OH
WITH 0-3 KM CAPE UP TO 100-125 J/KG. THESE FACTORS SUGGEST AN
INCREASED POTENTIAL FOR TORNADO DEVELOPMENT. IN ADDITION TO A
TORNADO THREAT...THE STEEP MIDLEVEL LAPSE RATES SUPPORT A THREAT FOR
HAIL.

..PETERS.. 05/18/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...AKQ...CTP...LWX...RNK...PBZ...RLX...

LAT...LON 37387587 37037850 38167976 39108069 40498128 40808051
40597846 39777696 39037648 37387587

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