MESO: Mesoscale Discussion 0631

ACUS11 KWNS 111744
SWOMCD
SPC MCD 111744
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-NCZ000-DCZ000-WVZ000-111915-

MESOSCALE DISCUSSION 0631
NWS STORM PREDICTION CENTER NORMAN OK
1244 PM CDT SAT MAY 11 2013

AREAS AFFECTED...CENTRAL/ERN PORTIONS OF MD AND VA...SERN
PA...DE...SRN NJ...NERN NC...

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 111744Z - 111915Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TSTMS ARE EXPECTED TO CONTINUE DEVELOPING THROUGH 20Z
AHEAD OF A COLD FRONT. THE STRONGER TSTMS WILL BE CAPABLE OF
DAMAGING WIND GUSTS AND PERHAPS MARGINALLY SEVERE HAIL. TRENDS ARE
BEING MONITORED AND A WW MAY BE NEEDED.

DISCUSSION...A MODERATELY UNSTABLE AIR MASS HAS DEVELOPED AHEAD OF A
COLD FRONT CURRENTLY MOVING THROUGH THE CENTRAL APPALACHIANS EARLY
THIS AFTERNOON. STRONG DIURNAL HEATING ACROSS MUCH OF THE DISCUSSION
AREA COMBINED WITH A SEASONABLY MOIST BOUNDARY LAYER WILL RESULT IN
MLCAPES OF 1000-1500 J/KG BY MID AFTERNOON. STRENGTHENING
LOWER-MID-TROPOSPHERIC FLOW HAS RESULTED IN SUFFICIENT DEEP-LAYER
SHEAR /AVERAGING 40KTS/ ACROSS THE AREA.

TSTMS ARE EXPECTED TO INCREASE IN COVERAGE NEAR A PRE-FRONTAL TROUGH
ACROSS NRN VA NWD INTO SERN PA/SRN NJ THIS AFTERNOON AS SOME
DECREASE IN CLOUD COVER ALLOWS FOR DESTABILIZATION. ORGANIZED
MULTICELLS/SHORT-LIVED BOWING SEGMENTS CAPABLE OF PRIMARILY DAMAGING
WIND GUSTS WILL BE POSSIBLE.

FARTHER SOUTH...THE AIR MASS IS MORE UNSTABLE OWING TO STRONGER
DIURNAL HEATING AND SCTD TSTMS HAVE DEVELOPED IN A CONFLUENT AXIS
FROM SERN VA SWD INTO ERN NC. SCTD TSTMS ARE ALSO DEVELOPING TO THE
WEST OF THIS AREA NEAR THE PRE-FRONTAL TROUGH. GIVEN PW VALUES OF
AROUND 1.25 INCHES AND STEEP LOW LEVEL LAPSE RATES...THE STRONGER
TSTMS THIS AFTN WILL BE CAPABLE OF LOCALLY DAMAGING WINDS AND
ISOLATED/MARGINALLY SEVERE HAIL.

CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED ACROSS THE
DISCUSSION AREA FOR A PSBL WW. A MORE TEMPORALLY/SPATIALLY LIMITED
THREAT ACROSS NRN PORTIONS OF THE DISCUSSION AREA LEADS TO GREATER
UNCERTAINTY REGARDING THE NEED FOR A WW.

..BUNTING/CARBIN.. 05/11/2013

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

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

LAT...LON 38407505 37217571 36427579 36107579 35797659 36227807
36557932 36857952 37497961 38827861 39487787 39847701
40097634 40257526 40207466 40057409 39557428 38407505

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