MESOSCALE DISCUSSION 0746
   NWS STORM PREDICTION CENTER NORMAN OK
   0355 PM CDT THU MAY 07 2009
   
   AREAS AFFECTED...SERN NEB...SWRN IA...NWRN MO...NERN KS
   
   CONCERNING...TORNADO WATCH 258...
   
   VALID 072055Z - 072200Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 258 CONTINUES.
   
   SUPERCELL POTENTIAL SHOULD INCREASE SUBSTANTIALLY DURING THE NEXT
   2-3 HOURS AS RICHER LOW-LEVEL MOISTURE CONTINUES TO SPREAD NEWD
   TOWARDS THE LOWER/MIDDLE MO RIVER VALLEY. LARGE HAIL WILL BE THE
   PRIMARY INITIAL THREAT WITH DAMAGING WIND/ISOLATED TORNADO THREATS
   INCREASING TOWARDS 00Z.
   
   AS 0F 2050Z...RADAR IMAGERY DEPICTED A CONGLOMERATE OF SHOWERS AND
   TSTMS ACROSS SWRN IA. THIS ACTIVITY APPEARS TO BE FORCED WITHIN A
   RELATIVELY TIGHT BAROCLINIC ZONE INVOF REMNANT OUTFLOW BOUNDARY.
   AMBIENT INSTABILITY JUST S OF ONGOING CONVECTION REMAINS MODEST
   OWING TO LOWER TO MIDDLE 50S F SURFACE DEW POINTS. HOWEVER...ROBUST
   MOISTENING CONTINUES UPSTREAM WITH AN AXIS OF MIDDLE 60S SURFACE DEW
   POINTS N OF THE I-70 CORRIDOR IN NERN KS. THIS WILL HELP PROMOTE
   RAPID DESTABILIZATION INTO THE MO RIVER VALLEY DURING THE NEXT 2-3
   HOURS WITH SUPERCELLS EXPECTED TO INCREASE IN COVERAGE/INTENSITY.
   
   ..GRAMS.. 05/07/2009
   
   
   ATTN...WFO...DMX...EAX...OAX...TOP...
   
   LAT...LON   40689236 39889243 39259326 38909444 39059620 39289649
               40149653 40729623 41049530 40909363 40689236