MESOSCALE DISCUSSION 1284
   NWS STORM PREDICTION CENTER NORMAN OK
   0724 AM CDT TUE JUN 23 2009
   
   AREAS AFFECTED...NORTHERN NEB/EASTERN SD INTO SOUTHWEST MN/NORTHWEST
   IA
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 494...
   
   VALID 231224Z - 231400Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 494
   CONTINUES.
   
   SEVERE TSTM WATCH 494 WILL LIKELY BE ALLOWED TO EXPIRE AS SCHEDULED
   AT 13Z. AN ADDITIONAL WATCH MAY BE NEEDED SOON FOR PORTIONS OF
   NORTHEAST NEB/EASTERN SD INTO SOUTHWEST MN/NORTHWEST IA.
   
   REMAINING BRUNT OF LONG-LIVED SMALL MCS CONTINUES TO STEADILY
   ADVANCE NORTHEASTWARD ACROSS NORTH CENTRAL NEB EARLY THIS
   MORNING...APPROACHING THE ONEILL AREA AS OF 1225Z. SHORT TERM
   DAMAGING WIND/HAIL THREAT WILL LIKELY CONTINUE ACROSS NORTHEAST
   NEB/FAR SOUTHEAST SD...BUT IT IS UNCLEAR IF/WHEN THIS ONGOING SEVERE
   CLUSTER MAY WANE IN INTENSITY. A SEEMINGLY WELL ESTABLISHED/BALANCED
   SURFACE COLD POOL MAY SUSTAIN THE ONGOING SEVERE MCS AT LEAST FOR
   THE NEXT FEW HOURS...WITH LIGHT S-SE SURFACE WINDS DOWNSTREAM...AND
   AN MCS-SUSTENANCE FAVORABLE TREND OF BACKING SOUTHEASTERLY WINDS
   WITHIN THE LOWEST 1 KM NOTED IN THE SIOUX FALLS WSR-88D VWP DATA
   OVER THE NEXT FEW HOURS. THE 12Z OBSERVED RAOB FROM OMAHA SAMPLES
   THE VERY STEEP MID LEVEL LAPSE RATE AND HIGHLY UNSTABLE ENVIRONMENT
   ON THE SOUTHERN PERIPHERY OF THIS MCS...AND EARLY MORNING VISIBLE
   SATELLITE IMAGERY DEPICTS AMPLE POTENTIAL FOR DOWNSTREAM HEATING
   ACROSS NORTHEAST NEB/SOUTHEAST SD INTO SOUTHWEST MN/NORTHWEST IA VIA
   CLOUD-FREE SKIES. FARTHER NORTH...ANOTHER RELATIVELY WEAKER REMNANT
   CONVECTIVE CLUSTER ACROSS EAST CENTRAL/NORTHEAST SD...WHICH PRODUCED
   A 44 KT GUST AT PIERRE AT AROUND 1110Z...MAY CONTINUE TO YIELD
   STRONG WIND GUSTS AS IT CONTINUES NORTHEASTWARD EARLY THIS MORNING.
   
   ..GUYER.. 06/23/2009
   
   
   ATTN...WFO...MPX...FSD...OAX...ABR...LBF...UNR...
   
   LAT...LON   41789851 41950014 42320154 43829971 44579937 45329963
               45489642 42409612 41789851