MESOSCALE DISCUSSION 1841
   NWS STORM PREDICTION CENTER NORMAN OK
   1049 PM CDT TUE AUG 21 2007
   
   AREAS AFFECTED...IA...PARTS OF SRN WI...NRN IL
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 635...
   
   VALID 220349Z - 220515Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 635
   CONTINUES.
   
   TRENDS WILL CONTINUE TO BE MONITORED FOR THE POSSIBILITY OF AN
   ADDITIONAL SEVERE WEATHER WATCH TO THE EAST/SOUTHEAST OF WWS 634 AND
   635.
   
   A WARM LOWER/MID TROPOSPHERIC AIR MASS MAY BE LIMITING THE HAIL
   POTENTIAL TO THE SOUTH OF THE MINNESOTA/IOWA BORDER AREA...BUT
   MERGING COLD POOLS APPEAR TO BE SLOWLY STRENGTHENING ACROSS
   NORTHWEST IOWA/EASTERN NEBRASKA.  THIS IS ON THE SOUTHERN FRINGE OF
   A STRONG WESTERLY MID/UPPER JET STREAK ASSOCIATED WITH A CENTRAL
   CANADIAN POLAR TROUGH...WHERE 35-45 KT 500 MB FLOW WILL MAINTAIN
   SUBSTANTIAL FORWARD PROPAGATION OF EVOLVING CONVECTIVE SYSTEM.  
   
   THE LATEST RUC GUIDANCE SUGGESTS THAT THE STRONGEST FORCING FOR
   UPWARD VERTICAL MOTION WILL SPREAD INTO THE INTERSTATE 80 CORRIDOR
   OF CENTRAL IOWA...NORTHEASTWARD INTO PARTS OF NORTHERN
   ILLINOIS/SOUTHERN WISCONSIN...TO THE NORTHEAST/EAST OF DUBUQUE BY
   06-07Z.  THE BOUNDARY LAYER ALONG A WEAK WARM FRONT ACROSS THIS
   REGION REMAINS WARM AND VERY MOIST...WITH TEMPERATURES STILL NEAR
   80F AND DEW POINTS IN THE UPPER 70S.  POTENTIAL FOR FURTHER
   INTENSIFICATION EXISTS...WITH AT LEAST THE CONTINUING RISK FOR
   LOCALLY HEAVY RAINFALL AND FREQUENT CLOUD TO GROUND LIGHTNING. 
   BUT...FURTHER STRENGTHENING OF THE COLD POOL COULD PROMOTE AN
   INCREASE IN POTENTIALLY DAMAGING SURFACE WIND GUSTS.
   
   ..KERR.. 08/22/2007
   
   
   ATTN...WFO...LOT...MKX...DVN...ARX...DMX...OAX...
   
   43049236 43609174 44119021 43948962 43328923 42568926
   41718962 41529078 41359150 41309301 41439431 41639546
   42419477 42649384