STORM2K

MESOSCALE DISCUSSION 0747
NWS STORM PREDICTION CENTER NORMAN OK
0926 PM CDT SUN MAY 04 2003

AREAS AFFECTED...SERN MO...NERN AR...NRN MS...WRN TN...WRN
KY...EXTREME SRN IL

CONCERNING...TORNADO WATCH 239...

VALID 050226Z - 050430Z

THREAT FOR STRONG TORNADOES CONTINUES WITHIN WW 239...AND IS
ESPECIALLY HIGH FROM WRN TN INTO WRN KY.

LATEST SURFACE ANALYSIS SHOWS PRESSURE RISE/FALL COUPLET FROM SERN
MO INTO WRN KY/TN. THE FALLS ARE CENTERED FROM WRN TN INTO WRN
KY...WITH VALUES UP TO 2 MB IN THE LAST HOUR ALONE...INDICATIVE OF
NWD RETURN OF MOIST UNSTABLE AIR SOUTH OF RETREATING WARM FRONT.
OBJECTIVE ANALYSIS SHOWS MODERATE INSTABILITY WITH MLCAPES UP TO
2500 J/KG.

PAH AND NQA VWPS SHOW TREMENDOUS LOW LEVEL HELICITY...WITH 0-3 KM
SRH VALUES OF 500-800 M2/S2. GIVEN HIGH LEVELS OF BOUNDARY LAYER RH
AND EXTREME SHEAR VALUES...ANY STORMS IN THIS ENVIRONMENT WILL HAVE
A HIGH PROBABILITY OF PRODUCING STRONG TORNADOES. HIGHEST THREAT
AREA IS OVER WRN TN AND KY...WHERE DEWPOINTS HAVE RISEN INTO THE
UPPER 60S F AND PRESSURES ARE FALLING THE FASTEST. THREAT COULD
EXTEND FURTHER N INTO SRN IL AND INDIANA LATER THIS EVENING AS WARM
FRONT RETREATS. A WW MAY BE REQUIRED N OF CURRENT WATCH BOX.

..JEWELL.. 05/05/2003