MESO: Mesoscale Discussion 1955

ACUS11 KWNS 180424
SWOMCD
SPC MCD 180423
NCZ000-SCZ000-GAZ000-180600-

MESOSCALE DISCUSSION 1955
NWS STORM PREDICTION CENTER NORMAN OK
1123 PM CDT MON SEP 17 2012

AREAS AFFECTED...NERN GA...WRN CAROLINAS

CONCERNING...TORNADO WATCH 640...

VALID 180423Z - 180600Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 640 CONTINUES.

SUMMARY...A MARGINAL/LOW-END TORNADO THREAT MAY GRADUALLY DEVELOP
E/NE OF WW 640. A DOWNSTREAM WW ISSUANCE IS NOT ANTICIPATED ATTM.

DISCUSSION...PRE-FRONTAL ARC OF N/S-ORIENTED CONVECTION HAS
STRUGGLED TO PRODUCE LIGHTNING IN NERN GA INTO THE WRN
CAROLINAS...WITH SOME LIGHTNING OBSERVED IN A CLUSTER ACROSS CNTRL
GA. LOW-LEVEL SHEAR CONTINUES TO INCREASE WITH 0-1 KM VALUES
APPROACHING 35 KT PER AREA VWP DATA. STILL...AMIDST A MEAGERLY
UNSTABLE AIR MASS CHARACTERIZED BY MLCAPE LARGELY AOB 500 J/KG PER
MODIFIED 00Z GSO RAOB AND ONLY MODEST SURFACE PRESSURE FALLS...THIS
ACTIVITY MAY STRUGGLE TO INTENSIFY. BUT A CONDITIONAL TORNADO RISK
DOES EXIST GIVEN THE STRENGTH OF THE LOW-LEVEL SHEAR...AND A
DOWNSTREAM WW ISSUANCE COULD BECOME NECESSARY IF LIGHTNING/ROTATION
TRENDS INCREASE.

..GRAMS.. 09/18/2012

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

ATTN...WFO...RAH...RNK...CHS...CAE...GSP...FFC...

LAT...LON 35528278 36408133 36398081 36198044 35858029 34768081
33408142 32658176 32188211 32118231 32168274 32458299
32878309 34038309 34938312 35528278

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