MESOSCALE DISCUSSION 0532
   NWS STORM PREDICTION CENTER NORMAN OK
   0819 PM CDT SUN APR 19 2009
   
   AREAS AFFECTED...CNTRL AL
   
   CONCERNING...TORNADO WATCH 174...
   
   VALID 200119Z - 200215Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 174 CONTINUES.
   
   TORNADO WATCH 173 IS SCHEDULED TO EXPIRE AT 02Z. HOWEVER...SEVERE
   THREAT IS EXPECTED TO PERSIST A COUPLE HOURS BEYOND THIS TIME...AND
   PORTIONS OF WW 173 WILL PROBABLY EITHER NEED TO BE EXTENDED IN TIME
   OR REPLACED WITH A NEW WATCH.
   
   WIDELY SCATTERED STORMS INCLUDING SUPERCELLS PERSIST ACROSS CNTRL
   AND N-CNTRL AL. NOCTURNAL COOLING SHOULD GRADUALLY STABILIZE THE
   BOUNDARY LAYER...AND INSTABILITY WILL BECOME INCREASINGLY MARGINAL
   WITH TIME. FURTHERMORE...THE BOUNDARY LAYER FLOW WILL SLOWLY VEER
   AND WEAKEN AS THE LOW LEVEL JET SHIFTS NEWD TOWARD THE SRN
   APPALACHIANS DURING THE EVENING. WHILE THESE PROCESSES SUGGEST THE
   SEVERE THREAT WILL DECREASE LATER THIS EVENING...THEY WILL NOT OCCUR
   QUICKLY ENOUGH TO MITIGATE THE SEVERE THREAT BEFORE WW 173 EXPIRES.
   IN THE MEANTIME HODOGRAPHS AND INSTABILITY WILL REMAIN SUFFICIENT TO
   SUSTAIN THE SEVERE THREAT FOR ANOTHER COUPLE HOURS.
   
   ..DIAL.. 04/20/2009
   
   
   ATTN...WFO...BMX...MOB...
   
   LAT...LON   34208570 33228533 32068535 31788682 32638759 33878673
               34208570