MESO: Mesoscale Discussion 0858

ACUS11 KWNS 211931
SWOMCD
SPC MCD 211930
ALZ000-FLZ000-212100-

MESOSCALE DISCUSSION 0858
NWS STORM PREDICTION CENTER NORMAN OK
0230 PM CDT MON MAY 21 2012

AREAS AFFECTED...PARTS OF SRN AL AND ADJACENT PORTIONS OF THE FL
PANHANDLE

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 211930Z - 212100Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED STRONG WIND GUSTS AND/OR HAIL APPROACHING 1 INCH
WILL BE POSSIBLE THROUGH THE AFTERNOON ACROSS PRIMARILY SOUTH
CENTRAL AL INTO ADJACENT COUNTIES IN THE FL PANHANDLE. GIVEN THE
LOW POTENTIAL FOR STORM ORGANIZATION...WW ISSUANCE IS UNLIKELY...BUT
IF A COLD POOL CAN BECOME ESTABLISHED...THEN A GREATER WIND THREAT
COULD DEVELOP. CONVECTIVE TRENDS WILL BE MONITORED.

DISCUSSION...SATELLITE IMAGERY SHOWED A SSEWD MOVING MCV OVER
CENTRAL AL /CENTERED 25 SW BHM AT 19Z/...WHILE A CORRIDOR OF HIGHER
THETAE/MODERATE INSTABILITY /MLCAPE UP TO 1500 J PER KG/ RESIDES
IMMEDIATELY DOWNSTREAM ACROSS SRN AL. ASCENT ATTENDANT TO THE SSEWD
MOVING MCV WILL REMAIN THE PRIMARY FORCING MECHANISM FOR UPWARD
VERTICAL MOTION AS LOW LEVEL CONVERGENCE REMAINS FAIRLY WEAK. SINCE
1830Z...TRENDS IN REGIONAL RADAR IMAGERY INDICATED AN INCREASE IN
UPDRAFTS/STORM INTENSITY FROM INVOF MGM WSWWD TO CLARKE/CHOCTAW
COUNTIES. ADDITIONAL SURFACE HEATING S OF THIS ACTIVITY WILL
FURTHER BOOST DCAPE VALUES TO AROUND 1000 J/KG AND MAINTAIN LARGE
TEMPERATURE/DEWPOINT SPREADS AROUND 30 DEGREES.

WEAK DEEP LAYER SHEAR IS EXPECTED TO LIMIT STORM ORGANIZATION...
THOUGH GIVEN THE HIGHER DCAPE VALUES AND DEWPOINT DEPRESSIONS...
STRONGER WIND GUSTS WILL BE POSSIBLE. THIS THREAT MAY BE ENHANCED
IF STORM MERGERS AID IN THE DEVELOPMENT OF A COLD POOL AND
SUBSEQUENT GUST POTENTIAL.

..PETERS/WEISS.. 05/21/2012

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

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

LAT...LON 31728790 31898753 31958695 32048651 32018646 31778610
31698583 31168555 30858600 30948765 31308792 31728790

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