MESOSCALE DISCUSSION 0439
   NWS STORM PREDICTION CENTER NORMAN OK
   0332 PM CDT FRI APR 15 2011
   
   AREAS AFFECTED...ERN MO / WRN-SWRN IL / WRN KY / NERN AR / NWRN TN
   
   CONCERNING...TORNADO WATCH 142...143...
   
   VALID 152032Z - 152130Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 142...143...CONTINUES.
   
   BROKEN LINE OF QUASI-DISCRETE STORMS WILL LIKELY MATURE/INTENSIFY
   INVOF THE MS RIVER THE NEXT FEW HOURS AS THE AIRMASS CONTINUES TO
   DESTABILIZE DOWNSTREAM OF ONGOING STRONG/SEVERE STORMS LOCATED NEAR
   OR W OF THE MS RIVER.
   
   20Z SURFACE ANALYSIS SHOWS A RELATIVELY NARROW PLUME OF RICHER LOW
   LEVEL MOISTURE /CHARACTERIZED BY UPPER 50S DEWPOINTS/ ADVECTING NWD
   OVER THE MS RIVER VALLEY FROM NERN AR/WRN TN NWD TOWARDS THE I-70
   CORRIDOR NEAR STL.  AMPLE SUNSHINE E OF THE BROKEN LINE IS
   CONTRIBUTING A PRONOUNCED THETA-E AXIS GENERALLY ALIGNING NNW-SSE
   FROM W-CNTRL IL SSEWD TO THE OH/MS RIVER CONFLUENCE AND S ALONG THE
   MS RIVER.
   
   AS THE UPPER SYSTEM CONTINUES TO APPROACH THE AREA...COLD TEMPS
   ALOFT /-20 TO -22 C AT H5/ SHOULD FOSTER HAIL GROWTH WITH THE MORE
   ROBUST UPDRAFTS.  STRONG LOW LEVEL SPEED/DIRECTIONAL SHEAR ON RUC
   FORECAST SOUNDINGS /200-300 M2/S2 EFFECTIVE SRH/ WILL PROBABLY ACT
   TO FOSTER LOW LEVEL ROTATION AS STORMS CONTINUE EWD TOWARDS THE
   INSTABILITY AXIS.  THIS IS WHERE THE SEVERE RISK /INCLUDING TORNADO/
   APPEARS GREATEST IN OVER THE NEXT 1-3 HRS AS STORMS ENCOUNTER THE
   STRONGER INSTABILITY AND LOW LEVEL SHEAR.
   
   ..SMITH.. 04/15/2011
   
   
   ATTN...WFO...PAH...ILX...MEG...LSX...DVN...
   
   LAT...LON   35999081 38309082 39899167 40249149 40059026 39478924
               37758873 36218902 35899012 35999081