MESO: Mesoscale Discussion 1757

ACUS11 KWNS 221921
SWOMCD
SPC MCD 221920
SCZ000-NCZ000-GAZ000-ALZ000-222145-

MESOSCALE DISCUSSION 1757
NWS STORM PREDICTION CENTER NORMAN OK
0220 PM CDT THU AUG 22 2013

AREAS AFFECTED...PORTIONS OF NRN AL...NRN/ERN GA...SC

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 221920Z - 222145Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...A VERY ISOLATED...MARGINAL SVR THUNDERSTORM POTENTIAL MAY
EXIST THIS AFTERNOON.

DISCUSSION...LOW-LEVEL ASCENT IS BEING MODESTLY ENHANCED WITHIN A
CORRIDOR INVOF A SUBTLE SFC WIND-SHIFT AXIS FROM NRN AL TO NRN GA
BENEATH THE NRN FRINGES OF A SUBTROPICAL RIDGE. OROGRAPHIC
CIRCULATIONS INVOF THE SRN APPALACHIANS AND SEA BREEZE BOUNDARIES
OVER THE SC COASTAL PLAIN ARE ALSO PROVIDING LOW-LEVEL LIFT. THESE
FACTORS WILL SUPPORT SOME INCREASE IN THUNDERSTORM ACTIVITY THIS
AFTERNOON AS THE BOUNDARY LAYER CONTINUES TO DESTABILIZE...WITH SFC
TEMPERATURES HAVING ALREADY INCREASED INTO THE MIDDLE/UPPER 80S
AMIDST SFC DEWPOINTS INTO UPPER 60S/LOWER 70S. A FEW VIGOROUS
UPDRAFTS/DOWNDRAFTS MAY OCCUR WITH GENERALLY DISORGANIZED
CONVECTION. AND...WITH GPS PW VALUES OF 1.5-1.8 INCHES...WATER
LOADING MAY SUPPORT A FEW STRONG DOWNBURSTS WITH LOCALLY STRONG SFC
WIND GUSTS...AND AN ISOLATED DMGG WIND GUST CANNOT BE RULED OUT.
HOWEVER...WITH GENERALLY 20 KT OR LESS OF FLOW IN THE LOWER/MIDDLE
TROPOSPHERE PER AREA VWP DATA...DEEP SHEAR IS NOT EXPECTED TO
SUPPORT ANY SUBSTANTIVE STORM ORGANIZATION...GREATLY LIMITING THE
SVR POTENTIAL AMIDST WEAK LOW-LEVEL AND DEEP ASCENT.

..COHEN/CORFIDI.. 08/22/2013

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

ATTN...WFO...ILM...CHS...CAE...GSP...MRX...FFC...BMX...HUN...

LAT...LON 32178082 32448154 33258268 33428509 33598734 34648712
34958470 35018172 34697993 34117886 33637869 32807940
32178082

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