MESO: Mesoscale Discussion 0278

ACUS11 KWNS 181812
SWOMCD
SPC MCD 181811
GAZ000-ALZ000-FLZ000-181945-

MESOSCALE DISCUSSION 0278
NWS STORM PREDICTION CENTER NORMAN OK
0111 PM CDT MON MAR 18 2013

AREAS AFFECTED...SCNTRL AL...WRN GA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 181811Z - 181945Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...A SEVERE THREAT IS LIKELY TO DEVELOP THIS AFTERNOON ACROSS
SCNTRL AL AND WRN GA. A FEW TORNADOES ALONG WITH A THREAT FOR
ISOLATED LARGE HAIL AND WIND DAMAGE WILL BE POSSIBLE WITH THE MORE
INTENSE CELLS. WW ISSUANCE WILL BE POSSIBLE FOR THIS AFTERNOON
ACROSS PARTS OF SRN AND ERN AL EXTENDING NEWD INTO WRN GA.

DISCUSSION...THUNDERSTORMS ARE BEGINNING TO DEVELOP ACROSS SCNTRL AL
AND IN THE WRN FL PANHANDLE AT THE ERN EDGE OF MODERATE INSTABILITY.
OBJECTIVE ANALYSIS SHOWS MLCAPE VALUES IN THE 1000 TO 1500 J/KG
RANGE ACROSS THE WRN PART OF THE MCD AREA AND INSTABILITY SHOULD
CONTINUE TO INCREASE OVER THE NEXT FEW HOURS. THE CELLS ARE
INITIATING IN A WEAKLY FORCED ENVIRONMENT DUE TO SFC HEATING BUT MAY
INCREASE IN COVERAGE AS A BAND OF LARGE-SCALE ASCENT APPROACHES LATE
THIS AFTERNOON. A MODERATE TO STRONG WIND SHEAR ENVIRONMENT EXISTS
ACROSS THE MCD AREA WITH 0-6 KM SHEAR ESTIMATED AT 40 TO 50 KT. IN
ADDITION...THE WSR-88D VWP IN SW AL SHOWS ABOUT 25 KT OF 0-1 KM
SHEAR WITH SUBSTANTIAL DIRECTIONAL SHEAR IN THE BOUNDARY LAYER. THIS
SHOULD ENABLE CELLS TO ROTATE AND SUPERCELL DEVELOPMENT WILL BE
POSSIBLE. A TORNADO AND ISOLATED LARGE HAIL THREAT SHOULD EXIST WITH
SUPERCELLS. WIND DAMAGE WILL ALSO BE POSSIBLE AS CELLS MATURE LATER
THIS AFTERNOON.

..BROYLES/HART.. 03/18/2013

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

ATTN...WFO...FFC...TAE...BMX...MOB...

LAT...LON 32828391 33118419 33258464 33228538 32998590 32458708
32128744 31798753 31238740 30898670 30928602 31138514
31958386 32828391

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