MESO: Mesoscale Discussion 1757

ACUS11 KWNS 140217
SWOMCD
SPC MCD 140217
MSZ000-LAZ000-ARZ000-140345-

MESOSCALE DISCUSSION 1757
NWS STORM PREDICTION CENTER NORMAN OK
0917 PM CDT MON AUG 13 2012

AREAS AFFECTED...CNTRL AND NRN MS THROUGH WRN AND WRN KY

CONCERNING...SEVERE THUNDERSTORM WATCH 577...578...

VALID 140217Z - 140345Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
577...578...CONTINUES.

SUMMARY...SEVERE STORM THREAT IS EXPECTED TO PERSIST THE REMAINDER
OF THIS EVENING FROM NERN LA AND ESPECIALLY CNTRL MS WITH ISOLATED
DAMAGING WIND AND LARGE HAIL THE MAIN CONCERNS. THREAT SHOULD REMAIN
MORE MARGINAL WITH STORMS OVER WRN KY AND NWRN TN.

DISCUSSION...THE CLUSTER OF STORMS OVER CNTRL MS APPEARS TO BE
EVOLVING INTO A FORWARD PROPAGATING SYSTEM ALONG CONSOLIDATED
OUTFLOW BOUNDARY. HOWEVER...A FEW DISCRETE CELLS REMAIN EMBEDDED
WITHIN THIS LOOSELY ORGANIZED MCS. STORMS ARE EXPECTED TO CONTINUE
SEWD NEXT FEW HOURS INTO AXIS OF MODERATELY INSTABILITY. WHERE
STORMS ARE CURRENTLY DEVELOPING...0-6 KM SHEAR IS ADEQUATE FOR
SUPERCELL STRUCTURES...ESPECIALLY AS STORMS INTERACT WITH EXTENSIVE
MODIFIED OUTFLOW BOUNDARY STRETCHING FROM SERN THROUGH CNTRL MS.
HOWEVER...STORMS WILL BEGIN TO SHIFT SOUTH OF STRONGER FLOW ALOFT BY
03Z OR 04Z...WHICH IN ADDITION TO STORM MERGERS AND POSSIBLE UPSCALE
GROWTH ALONG OUTFLOW BOUNDARIES SUGGEST ACTIVITY SHOULD BECOME
PREDOMINANT MULTICELLULAR IN CHARACTER.

FARTHER NORTH OTHER STORMS CONTINUE DEVELOPING ALONG THE SEWD
ADVANCING COLD FRONT. THIS ACTIVITY HAS EVOLVED INTO A LINE AND
COULD POSE A MODEST THREAT FOR ISOLATED STRONG WIND GUSTS NEXT HOUR
OR TWO. HOWEVER...OVERALL THREAT FROM WRN TN INTO WRN KY IS EXPECTED
TO REMAIN MARGINAL DUE TO WEAK INSTABILITY AS SAMPLED BY THE 00Z
NASHVILLE RAOB.

..DIAL.. 08/14/2012

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

ATTN...WFO...MEG...JAN...

LAT...LON 33828838 33088849 32568903 32469015 32689142 32989163
34198975 33828838

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