MESOSCALE DISCUSSION 0747
   NWS STORM PREDICTION CENTER NORMAN OK
   0542 PM CDT THU MAY 07 2009
   
   AREAS AFFECTED...NERN KS...SRN IA...NRN MO...WRN IL
   
   CONCERNING...TORNADO WATCH 258...
   
   VALID 072242Z - 080045Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 258 CONTINUES.
   
   LATEST SURFACE OBSERVATIONS INDICATE DEWPOINTS ACROSS MUCH OF THE
   TORNADO WATCH ARE IN THE 50S F RESULTING IN SURFACE T/TD SPREADS OF
   20-30 F. ALTHOUGH MID 60S F DEWPOINTS EXIST IN THE MOIST AXIS FROM
   JUST SW OF TOP KS SWD...LOW LEVEL FLOW AND MOISTURE TRANSPORT REMAIN
   MODEST WITH MEAN 2KM FLOW OF 15-20 KT.
   
   STORMS SHOULD CONTINUE TO REDEVELOP ACROSS THE WARM FRONT ZONE FROM
   SRN IA INTO NRN MO AS THE SWLY FEED OF UNSTABLE AIR PERSISTS. MOST
   MODELS INDICATE THAT SOME STRENGTHENING OF THE LOW LEVEL JET WILL
   OCCUR INTO THE 20-25 KT RANGE. THIS MAY INCREASE LOW LEVEL
   SHEAR...BUT LOW LEVEL WINDS WILL ALSO VEER GRADUALLY WITH TIME GIVEN
   RELATIVELY ZONAL FLOW ALOFT. THE END RESULT SHOULD BE TRAINING
   ECHOES GRADUALLY SHIFTING SEWD AND POSSIBLY GROWING UPSCALE INTO AN
   MCS. IF THIS OCCURS...THE PRIMARY THREATS WILL BE WIND AND HAIL. 
   
   A TORNADO THREAT MAY INCREASE LATER THIS EVENING AS LOW LEVEL
   MOISTURE AND SHEAR INCREASE. MUCH WILL DEPEND ON STORM MODE BY THAT
   TIME...AS CURRENT BOUNDARY LAYER CONDITIONS ACROSS THE TORNADO WATCH
   FAVOR STRONG OUTFLOW PRODUCTION. IF MID 60S F DEWPOINTS CAN ADVECT
   NEWD INTO THE SWRN PORTION OF THE STORM GENERATION ZONE NEAR THE
   DRYLINE/WARM FRONT INTERSECTION...THERE COULD BE A TORNADO THREAT.
   THIS WOULD MOST LIKELY OCCUR OVER FAR NERN KS AND NWRN MO.
   
   ..JEWELL.. 05/07/2009
   
   
   ATTN...WFO...ILX...LSX...DVN...DMX...EAX...OAX...TOP...
   
   LAT...LON   39499034 39079132 39189224 39399357 39469424 39029477
               38829573 39249630 39349620 39829585 40329581 40909561
               41149496 41249346 41129289 40629177 40189069 39499034