MESO: Mesoscale Discussion 1679

ACUS11 KWNS 091918
SWOMCD
SPC MCD 091917
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-092015-

MESOSCALE DISCUSSION 1679
NWS STORM PREDICTION CENTER NORMAN OK
0217 PM CDT FRI AUG 09 2013

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

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 091917Z - 092015Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE THROUGH THE
AFTERNOON ACROSS SERN PA...ERN AND SRN MD...AND NERN VA...WITH
ACTIVITY SPREADING EWD INTO NJ AND THE DELMARVA REGION. A LACK OF
STRONGER LOW LEVEL CONVERGENCE IN THE DISCUSSION AREA...TO THE EAST
OF THE COLD FRONT...SUGGESTS ADDITIONAL STORM DEVELOPMENT WILL BE
SCATTERED. STRONGER STORMS WILL BE CAPABLE OF PRODUCING A DAMAGING
WET MICROBURST. IF GREATER UPSCALE GROWTH OR STORM CONSOLIDATION
CAN OCCUR...THEN A WATCH MAY BE NEEDED.

DISCUSSION...DESPITE THE LACK OF STRONGER MIDLEVEL LAPSE
RATES...STRONG SURFACE HEATING /LOWER 90S INTO NERN-ERN VA/ AND
MID-UPPER 80S IN SERN PA/ADJACENT NJ/ WITHIN A RATHER MOIST AIR MASS
/PW EXCEEDING 2 INCH/ IS RESULTING IN MODERATE INSTABILITY. FORCING
FOR ASCENT AHEAD OF A MIDLEVEL TROUGH...NOW MOVING THROUGH THE
CENTRAL APPALACHIANS...WILL SPREAD EWD INTO THE STRONGER INSTABILITY
AIDING IN ADDITIONAL STORM DEVELOPMENT. SURFACE ANALYSES SHOWED A
LEE TROUGH EXTENDING SSWWD FROM ERN PA THROUGH MD /ALONG THE I-95
CORRIDOR/ INTO CENTRAL VA. SOME STORMS MAY BE TIED TO THIS
FEATURE...THOUGH WEAK LOW LEVEL CONVERGENCE ALONG THIS BOUNDARY
ESPECIALLY INTO CENTRAL VA SUGGESTS STORM COVERAGE WILL BE LIMITED
WITH SWD EXTENT. LAST SEVERAL RUNS OF THE HRRR CONFIRM THIS SCENARIO
WITH SCATTERED STORM DEVELOPMENT CONTINUING THROUGH THE AFTERNOON
FROM SERN PA TO NERN VA AND SPREADING EWD. AREA VAD WIND DATA
INDICATED 40-50 KT WLY MIDLEVEL WINDS CONTRIBUTING TO EFFECTIVE BULK
SHEAR SUFFICIENT FOR MULTICELLS AND SUPERCELLS...WHILE RELATIVELY
STRAIGHT HODOGRAPHS ALSO SUPPORT STORM SPLITS.

THE PRESENCE OF WEAK MIDLEVEL LAPSE RATES WILL TEND TO LIMIT
ROBUST...VIGOROUS UPDRAFTS...THOUGH THE AVAILABLE CAPE/SHEAR
PARAMETER SPACE WILL SUPPORT SOME ORGANIZED STORMS.

..PETERS/WEISS.. 08/09/2013

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

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

LAT...LON 39697635 40457558 40417497 40217448 39357489 38827553
38177624 38127687 38537728 39697635

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.