MESO: Mesoscale Discussion 0400

ACUS11 KWNS 051903
SWOMCD
SPC MCD 051902
OHZ000-KYZ000-INZ000-TNZ000-ILZ000-MOZ000-ARZ000-052030-

MESOSCALE DISCUSSION 0400
NWS STORM PREDICTION CENTER NORMAN OK
0202 PM CDT SUN APR 05 2009

AREAS AFFECTED...CNTRL/SRN IL AND IND...SWD THRU WRN/CNTRL KY AND
WRN TN

CONCERNING...TORNADO WATCH 117...

VALID 051902Z - 052030Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 117 CONTINUES.

RISK FOR TORNADOES AND DAMAGING WIND GUSTS WILL INCREASE IN
DEVELOPING STORMS THIS AFTERNOON.

WEAK WARM SECTOR BOUNDARY LAYER DESTABILIZATION IS ONGOING...WITH
LOW-LEVEL MOISTURE RETURN ACROSS WESTERN TENNESSEE AND KENTUCKY INTO
THE VICINITY OF THE WARM FRONT EXTENDING ACROSS CENTRAL INDIANA AND
ILLINOIS. WITH FURTHER SURFACE HEATING...MIXED LAYER CAPE MAY STILL
INCREASE OVER CURRENT VALUES NOW AROUND 500 J/KG.

LOW-LEVEL WARM ADVECTION ALONG/EAST OF A PRE-FRONTAL THERMAL RIDGE
...NOW EXTENDING ACROSS WESTERN TENNESSEE AND KENTUCKY INTO SOUTHERN
INDIANA...PROBABLY WILL REMAIN A FOCUS FOR DISCRETE CONVECTIVE
DEVELOPMENT AS IT SLOWLY SHIFTS EASTWARD THROUGH 22-23Z.
AND...THESE STORMS ARE EXPECTED TO PROVIDE THE GREATEST POTENTIAL
FOR TORNADIC DEVELOPMENT. LOW-LEVEL HODOGRAPHS ACROSS THIS AREA
REMAIN CLOCKWISE CURVED...ARE ALREADY SIZABLE...AND MAY ENLARGE
FURTHER WITH SOME STRENGTHENING OF A SOUTHWESTERLY LOW-LEVEL JET
PROGGED /FROM 30-40+ KT/ AHEAD OF A SLOWLY DEEPENING SURFACE LOW
MIGRATING NORTH OF THE OHIO RIVER...ACROSS SOUTHERN ILLINOIS INTO
SOUTHERN INDIANA.

MEANWHILE...STRENGTHENING FRONTOGENETIC FORCING ALONG THE COLD FRONT
IS EXPECTED TO SUPPORT THE CONTINUED EVOLUTION OF A SQUALL LINE...AS
THE FRONT ADVANCES EAST OF THE MISSISSIPPI RIVER DURING THE NEXT FEW
HOURS. SHEAR PROFILES IN CLOSE PROXIMITY TO THE FRONT ARE BECOMING
MORE UNIDIRECTIONAL...BUT DOWNWARD TRANSPORT OF MOMENTUM SHOULD
CONTRIBUTE TO INCREASING POTENTIAL FOR DAMAGING WIND GUSTS BY LATE
AFTERNOON...AS A 100 KT 500 MB JET STREAK NOSES INTO THE LOWER OHIO
VALLEY.

..KERR.. 04/05/2009

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

ATTN...WFO...ILN...LMK...OHX...IND...PAH...ILX...MEG...

LAT...LON 37278907 39188752 39478563 39098472 38518497 37868558
37048686 36488750 35618886 35339001 36258968 37278907

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