MESO: Mesoscale Discussion 1204

ACUS11 KWNS 181540
SWOMCD
SPC MCD 181540
NJZ000-PAZ000-DEZ000-VAZ000-MDZ000-DCZ000-181715-

MESOSCALE DISCUSSION 1204
NWS STORM PREDICTION CENTER NORMAN OK
1040 AM CDT THU JUN 18 2009

AREAS AFFECTED...SERN PA INTO NJ AND SWD THROUGH THE DELMARVA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 181540Z - 181715Z

THE THREAT FOR SEVERE STORMS INCLUDING SUPERCELLS CAPABLE OF
HAIL...DAMAGING WINDS AND PERHAPS TORNADOES IS EXPECTED TO INCREASE
THIS AFTERNOON. CONVECTIVE TRENDS ARE BEING MONITORED FOR A
POSSIBLE WW.

LATEST MESOANALYSIS INDICATED A WEAK SURFACE LOW OVER CNTRL MD INTO
S-CNTRL/SERN PA WHICH IS FORECAST TO DEVELOP SLOWLY EWD/SEWD THIS
AFTERNOON PER 12Z MODEL GUIDANCE. AS THIS OCCURS...ATTENDANT WARM
FRONT EXTENDING FROM THE LOW SSEWD THROUGH CHESAPEAKE BAY SHOULD
DEVELOP EWD/NEWD THROUGH PARTS OF ERN MD...DE AND PERHAPS SRN NJ.

WARM SECTOR AIR MASS IN PLACE OVER CNTRL/ERN VA INTO CNTRL MD IS
QUITE MOIST WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S. WHEN
COUPLED WITH THE AFTERNOON HEATING...AIR MASS WILL FURTHER
DESTABILIZE WITH MLCAPE APPROACHING 1000-2000 J/KG. AS
SUCH...EXPECT CONVECTION CURRENTLY DEVELOPING FROM SERN PA THROUGH
CNTRL MD INTO NRN VA TO INTENSIFY THIS AFTERNOON WITH ADDITIONAL
TSTM DEVELOPMENT LIKELY INTO CNTRL/ERN VA ALONG SEWD-MOVING
TROUGH/COLD FRONT.

CURRENT AREA VWPS INDICATE THE STRONGEST LOW-LEVEL SHEAR E OF WARM
FRONT /REF. CURRENT DOX WIND PROFILE/ WITH NOTABLY WEAKER LOW-LEVEL
WIND FIELDS WITHIN WARM SECTOR. NONETHELESS...THE PRESENCE OF THE
MODERATE INSTABILITY...30-40 KT OF DEEP LAYER SHEAR AND
ISALLOBARICALLY BACKED SURFACE WINDS INVOF LOW AND WARM FRONT
SUGGESTS THE POTENTIAL FOR A FEW SUPERCELLS CAPABLE OF
HAIL...DAMAGING WINDS AND PERHAPS A FEW TORNADOES.

..MEAD.. 06/18/2009

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

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

LAT...LON 37707829 39027762 40007706 40417636 40437556 40317493
39537483 38467573 37467621 36997679 37107796 37707829

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