MESO: Mesoscale Discussion 1949

ACUS11 KWNS 171759
SWOMCD
SPC MCD 171758
ALZ000-FLZ000-MSZ000-LAZ000-171930-

MESOSCALE DISCUSSION 1949
NWS STORM PREDICTION CENTER NORMAN OK
1258 PM CDT MON SEP 17 2012

AREAS AFFECTED...FAR SE LA...SRN MS AND SW AL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 171758Z - 171930Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...A SEVERE THREAT IS EXPECTED TO DEVELOP ACROSS THE REGION
THIS AFTERNOON. ROTATING CELLS COULD POSE A THREAT FOR TORNADOES. WW
ISSUANCE MAY BE REQUIRED.

DISCUSSION...SEVERAL BANDS OF STORMS ARE CURRENTLY ONGOING FROM FAR
SE LA EXTENDING NEWD INTO THE VICINITY OF MOBILE AL. THIS ACTIVITY
IS LOCATED JUST AHEAD OF A SHORTWAVE TROUGH AND WELL-DEFINED
VORTICITY MAXIMA EVIDENT ON WATERY VAPOR IMAGERY NEAR THE MS RIVER
DELTA. FORCING ASSOCIATED WITH THE VORT MAX AND SFC HEATING WILL
HELP THE STORM ORGANIZATION THIS AFTERNOON. IN ADDITION...THE
WSR-88D VWPS AT MOBILE AND NEW ORLEANS SHOW INCREASING LOW-LEVEL
SHEAR WITH TIME WITH 0-1 KM SHEAR AROUND 25 KT AND 0-6 KM SHEAR OF
30 TO 40 KT. THIS AMOUNT OF SHEAR SHOULD BE SUPPORTIVE OF ROTATING
CELLS AND AN ISOLATED TORNADO THREAT IS EXPECTED TO DEVELOP THIS
AFTERNOON. WIND DAMAGE POTENTIAL COULD ALSO DEVELOP ESPECIALLY IF
INSTABILITY CAN INCREASE AHEAD OF THE ACTIVITY IN SRN MS AND SRN AL.

..BROYLES/MEAD.. 09/17/2012

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

ATTN...WFO...BMX...MOB...JAN...LIX...

LAT...LON 32088816 32098903 31688956 30828967 29908975 29238979
29038908 29528852 30358755 31348725 32088816

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