MESO: Mesoscale Discussion 1744

ACUS11 KWNS 211849
SWOMCD
SPC MCD 211848
OHZ000-212115-

MESOSCALE DISCUSSION 1744
NWS STORM PREDICTION CENTER NORMAN OK
0148 PM CDT WED AUG 21 2013

AREAS AFFECTED...PORTIONS OF OHIO

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 211848Z - 212115Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...THE POTENTIAL FOR ISOLATED STRONG THUNDERSTORMS WILL EXIST
THROUGH THE AFTERNOON...AND A MARGINALLY SEVERE THUNDERSTORM CANNOT
BE RULED OUT.

DISCUSSION...VISIBLE SATELLITE LOOPS INDICATE AN ARC OF ISOLATED TO
WIDELY SCATTERED CONVECTION EXTENDING FROM S OF THE COLUMBUS METRO
AREA TO NW OF DAYTON...LIKELY A MANIFESTATION OF ENHANCED MID-LEVEL
UPWARD MOTION PRECEDING AN APPROACHING CYCLONE PER WATER VAPOR
IMAGERY. ADDITIONAL CONVECTION CONTINUES TO FORM FROM SERN INDIANA
INTO NRN KY IN CLOSER PROXIMITY TO THE CYCLONE CENTER. DCVA
PRECEDING THE CYCLONE WILL CONTINUE TO MAINTAIN AN ENVIRONMENT
FAVORABLE FOR ISOLATED TO SCATTERED STORMS THROUGH THE AFTERNOON.

DESTABILIZATION OF THE FAIRLY MOIST BOUNDARY LAYER IN AREAS VOID OF
PRIOR CONVECTIVE OVERTURNING CONTINUES AS SFC TEMPERATURES HAVE
INCREASED INTO THE MIDDLE 80S AMIDST DEWPOINTS IN THE LOWER/MIDDLE
60S TO THE S OF A SUBTLE...WNW/ESE-ORIENTED BOUNDARY THAT EXTENDS
THROUGH CENTRAL/W-CENTRAL OHIO. THIS BOUNDARY COULD EDGE SLIGHTLY
NWD THROUGH THE AFTERNOON OWING TO THE DEEPER CIRCULATION IN THE ERN
SEMICIRCLE OF CYCLONE...FOSTERING SOME ADDITIONAL NWD
DESTABILIZATION...PERHAPS INTO N-CNTRL OHIO.

MODIFICATIONS TO THE 12Z WILMINGTON OHIO RAOB INDICATE MLCAPE VALUES
IN EXCESS OF 2000 J/KG IN LOCATIONS WHERE STRONG DIABATIC SFC
HEATING HAS OCCURRED S OF THE AFOREMENTIONED BOUNDARY...AIDED BY
COOL 500-MB TEMPERATURES AROUND -12C TO -10C INVOF THE CYCLONE. THIS
MAY SUPPORT A FEW VIGOROUS UPDRAFTS/DOWNDRAFTS WITH SMALL HAIL AND
GUSTY SFC WINDS BEING THE MAIN CONCERNS. DESPITE MODEST HIGH-LEVEL
FLOW SUPPORTING SOME CONVECTIVE VENTILATION...VWP DATA FROM
WILMINGTON INDICATE 15 KT OR LESS OF LOW/MID TROPOSPHERIC FLOW AND
WEAK DEEP SHEAR OWING TO LIMITED HEIGHT GRADIENTS IN PROXIMITY TO
THE CYCLONE. THIS SHOULD LARGELY MITIGATE CONVECTIVE
ORGANIZATION...THOUGH AN ISOLATED INSTANCE OF MARGINALLY SVR HAIL OR
A DMGG WIND GUST CANNOT BE ENTIRELY RULED OUT.

..COHEN/CORFIDI.. 08/21/2013

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

ATTN...WFO...PBZ...RLX...CLE...ILN...IWX...

LAT...LON 39378180 39258340 38848405 39948448 40658455 41208402
41308305 40758208 39978147 39378180

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