MESOSCALE DISCUSSION 1333
   NWS STORM PREDICTION CENTER NORMAN OK
   0902 PM CDT MON JUN 20 2011
   
   AREAS AFFECTED...SERN SD...SWRN MN...NERN NEB...WRN IA
   
   CONCERNING...TORNADO WATCH 526...
   
   VALID 210202Z - 210300Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 526 CONTINUES.
   
   NWD-PROPAGATING PORTION OF 600+ MILE LONG QLCS HAS BOWED ACROSS SERN
   SD...WITH COMMA HEAD CENTERED OVER HUTCHINSON COUNTY. ALTHOUGH
   CURRENT PROPAGATION WILL RESULT IN MOVEMENT INTO A LESS UNSTABLE AIR
   MASS WITH NRN EXTENT...DAMAGING WIND/ISOLATED TORNADO THREAT SHOULD
   DEVELOP N OF WW 526...AND MAY NECESSITATE A WFO WW EXTENSION.
   
   FARTHER S...TSTM DEVELOPMENT HAS OCCURRED ALONG QUASI-STATIONARY
   FRONTAL AXIS JUST E OF BOWING SEGMENT THAT RECENTLY PASSED ALONG AND
   N OF THE OMAHA METRO AREA WITH MEASURED SEVERE WIND GUSTS. WITH A
   VERY UNSTABLE AIR MASS LYING S OF THE FRONTAL BOUNDARY...AND
   ENLARGING LOW-LEVEL HODOGRAPHS EVIDENT IN DES MOINES VWP
   DATA...GREATEST RELATIVE DAMAGING WIND/TORNADO RISK SHOULD EVOLVE
   ACROSS PORTIONS OF THE I-80 TO US-20 CORRIDORS IN W-CNTRL IA.
   
   ..GRAMS.. 06/21/2011
   
   
   ATTN...WFO...MPX...DMX...FSD...OAX...
   
   LAT...LON   43149826 43439850 43919833 44309807 44489727 44449641
               44139550 43779490 43399460 42919435 41869384 41539384
               41559454 41509559 41579585 42389644 42999719 43149826