959 
ACUS11 KWNS 211844
SWOMCD
SPC MCD 211842
MOZ000-ILZ000-212100-

SPC MESOSCALE DISCUSSION 0471 FOR SERN MO / SRN IL...
CONCERNING...SEVERE THUNDERSTORM WATCH 136...

THUNDERSTORMS INCREASING FROM NEAR STL SWWD TO JUST N OF UNO. 
LARGE HAIL AND DAMAGING WIND THREAT INCREASING.  TORNADO THREAT MAY
ALSO INCREASE NEAR LOW CENTER INTO CENTRAL IL.  UPGRADE TO TORNADO
WW MAY BE REQUIRED.

LATEST SURFACE ANALYSIS SHOWS LOW NOW JUST N OF STL...WITH WAVY
COLD FRONT EXTENDING SWWD INTO N CENTRAL AR.  WITH TEMPERATURES NOW
IN THE UPPER 70S TO LOW 80S AND DEWPOINTS IN THE UPPER 60S...
SIGNIFICANT DESTABILIZATION CONTINUES ACROSS MUCH OF WW AREA WHERE
SURFACE-BASED CAPE IS NOW 2000 TO 3000 J/KG.  ALTHOUGH BOUNDARY
LAYER FLOW WITHIN WARM SECTOR REMAINS VEERED RESULTING IN
RELATIVELY WEAK SURFACE CONVERGENCE AND LOW-LEVEL SHEAR...LINE OF
STORMS CONTINUES TO SLOWLY INCREASE.

WITH MODERATE LOW-LEVEL WSWLY FLOW AND 70 KTS AT MID-LEVELS
ACCORDING TO BLM PROFILER...KINEMATIC FIELD REMAINS FAVORABLE FOR
SUPERCELLS AND BOWS / LEWPS.  ALTHOUGH DAMAGING WINDS AND LARGE
HAIL APPEAR TO REMAIN THE PRIMARY SEVERE THREAT...STRONGER LOW-
LEVEL SHEAR EXISTS ACROSS NRN PORTIONS OF WW WHERE SURFACE WINDS
ARE MORE BACKED NEAR LOW / WARM FRONT SUGGESTING THE HIGHEST
TORNADO THREAT LIKELY EXISTS ACROSS THIS REGION.

..GOSS.. 04/21/02