[LeArc] SPC MESOSCALE DISCUSSION FOR ERN IA, SERN MN, SRN WI, NWRN IL.

[Duane Whittingham]

SPC MESOSCALE DISCUSSION 1760 FOR ERN IA...SERN MN...SRN WI...
NWRN IL. 

CONCERNING...SEVERE THUNDERSTORM POTENTIAL...
VALID 211831Z - 212200Z 

THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE NEXT 1-2 HRS. 
DAMAGING WINDS ALONG WITH VERY HEAVY RAIN WOULD BE THE MAIN SEVERE 
THREATS.

LATEST SURFACE ANLYSIS DEPICTED A RETREATING WARM FRONT DRAPED
ACROSS THE IA/MN BORDER EWD INTO SRN WI.  THE AIRMASS ALONG AND
SOUTH OF THE BOUNDARY HAS BECOME VERY UNSTABLE WITH MLCAPES OF 
2500-3500 J/KG.  MODIFIED 18Z DVN SOUNDING SHOWS COOLER THAN 
PROGGED MID LEVEL TEMPERATURES AND THEREFORE MORE FAVORABLE LAPSE 
RATES FOR SEVERE CONVECTION...ALTHOUGH HAIL APPEARS TO BE A MINIMAL
THREAT. 

THE DICUSSION AREA IS ESSENTIALLY UNCAPPED AS OF 1830Z...
SO CONVECTION IS EXPECTED TO FORM WITHIN THE NEXT COUPLE HOURS. 
LATEST VISIBLE IMAGERY SHOWS INCREASING CU INTO ERN IA. 
THIS IS IN INSTABILITY AXIS AND AHEAD OF PRESSURE FALL LOBE AT 
SURFACE.  STORMS MAY FORM HERE AND OR ALONG WARM FRONT. AREA IS
BEING MONITORED FOR A POSSIBLE WW. 

..JEWELL.. 08/21/02
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Duane Whittingham (N9SSN) - Producer
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