Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS11 KWNS 211931
SWOMCD
SPC MCD 211930
NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-212130-

MESOSCALE DISCUSSION 1594
NWS STORM PREDICTION CENTER NORMAN OK
0230 PM CDT THU AUG 21 2014

AREAS AFFECTED...PARTS OF CNTRL/SERN PENNSYLVANIA...CNTRL/SRN NEW
JERSEY...CNTRL/ERN MARYLAND...DELAWARE...N CNTRL VIRGINIA AND THE
DISTRICT OF COLUMBIA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 211930Z - 212130Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...THE RISK FOR STRONG TO SEVERE STORM DEVELOPMENT MAY
INCREASE ACROSS PORTIONS OF THE NORTHERN MID ATLANTIC COAST
REGION...PARTICULARLY NEAR/SOUTH OF PHILADELPHIA THROUGH THE 22-00Z
TIME FRAME.  SOME UNCERTAINTY PERSISTS CONCERNING THE EXTENT OF THE
SEVERE WEATHER POTENTIAL...BUT AN ISOLATED SUPERCELL OR TWO MAY NOT
BE OUT OF THE QUESTION.  WHILE THE NEED FOR A WATCH CURRENTLY
APPEARS UNLIKELY...TRENDS WILL CONTINUE TO BE CLOSELY MONITORED.

DISCUSSION...BENEATH A LAYER OF MID-LEVEL DRYING...TO THE SOUTH AND
SOUTHEAST OF AN ELONGATED CYCLONIC CIRCULATION OVER THE LOWER GREAT
LAKES REGION...SCATTERED THUNDERSTORM DEVELOPMENT IS NOW WELL
UNDERWAY EAST SOUTHEAST OF THE LOWER GREAT LAKES REGION...TOWARD THE
NORTHERN MID ATLANTIC COAST.  MODELS SUGGEST THAT MID-LEVEL LAPSE
RATES REMAIN GENERALLY WEAK...LIMITING CAPE FOR MIXED BOUNDARY LAYER
PARCELS ACROSS THE REGION TO SEASONABLY MODEST VALUES ON THE ORDER
OF 1000-1500 J/KG.  HOWEVER...30-40 KT WEST NORTHWESTERLY 500 MB
FLOW ACROSS MUCH OF PENNSYLVANIA INTO NORTHERN MID ATLANTIC COASTAL
AREAS DOES APPEAR TO BE CONTRIBUTING TO SUFFICIENT VERTICAL SHEAR
FOR MID-LEVEL UPDRAFT ROTATION.

WITH ADDITIONAL SURFACE HEATING...A CONTINUED GRADUAL
INTENSIFICATION OF STRONGER CELLS APPEARS POSSIBLE AS ACTIVITY
DEVELOPS EAST OF THE HIGHER TERRAIN TOWARD COASTAL AREAS.  A WEAK
SURFACE LOW/WARM FRONTAL ZONE NEAR AND WEST THROUGH SOUTH OF THE
PHILADELPHIA METRO AREA MAY PROVIDE THE FOCUS FOR THE STRONGEST
/MOST CONCENTRATED ACTIVITY BY 23-00Z...WITH THE ENVIRONMENT AT
LEAST MARGINALLY SUFFICIENT FOR SUPERCELLS.

..KERR/DIAL.. 08/21/2014

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

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

LAT...LON   40877803 40757526 40247407 39037516 38727630 38727694
            39267778 39497780 40107809 40877803



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