MESOSCALE DISCUSSION 0570
   NWS STORM PREDICTION CENTER NORMAN OK
   0733 PM CDT TUE APR 24 2007
   
   AREAS AFFECTED...PORTIONS N-CENTRAL/NE TX INCLUDING
   METROPLEX...EXTREME SERN OK...WRN AR...EXTREME SWRN MO.
   
   CONCERNING...TORNADO WATCH 174...176...177...
   
   VALID 250033Z - 250230Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH
   174...176...177...CONTINUES.
   
   THOSE COUNTIES OF ORIGINAL 174 FROM BROWN/COMANCHE/HAMILTON SWWD
   HAVE BEEN INCORPORATED INTO NEWER WW 179.  WW 174 IS SCHEDULED TO
   EXPIRE AT 1Z...BUT WITH POTENTIAL FOR SVR CONVECTION REMAINING OVER
   AREA FROM STEPHENS/PALO PINTO COUNTIES ENEWD ACROSS METROPLEX
   ATTM...WW MAY BE LOCALLY EXTENDED FOR A COUPLE HOURS TO COVER THOSE
   AREAS.  GIVEN FAVORABLE ENVIRONMENT EVIDENT IN ITS PATH...RELATIVELY
   DISCRETE PALO PINTO COUNTY STORM MAY BECOME SUPERCELLULAR AND MOVE
   TOWARD SWRN PORTIONS METROPLEX.  FARTHER NE...DAMAGING WIND REPORTED
   IN MCCURTAIN COUNTY OK DURING PAST HOUR FROM  BOW ECHO MOVING TOWARD
   NERN CORNER OF WW 176 AND SERN PORTION WW 177...WITH POTENTIAL FOR
   ADDITIONAL DAMAGING GUSTS SEVIER/HOWARD/POLK/MONTGOMERY/PRICE
   COUNTIES AR.  SVR POTENTIAL FARTHER N IS MORE MRGL...PARTICULARLY
   ACROSS OZARKS WHERE SFC ANALYSIS SHOWS PERSISTENT COOL POCKET THAT
   IS MINIMIZING THETAE IN INFLOW LAYER.  RELATIVELY WEAK BUOYANCY AND
   LAPSE RATES EVIDENT IN LZK SOUNDING ALSO MAY PORTEND MRGL SVR
   POTENTIAL EWD OVER CENTRAL/NRN AR. 
   
   PRE-STORM AIR MASS FROM SWRN AR SWWD ACROSS N-CENTRAL TX REMAINS
   FAVORABLE FOR SVR BASED ON 00Z FWD RAOB...PAT PROFILER
   DATA...VARIOUS VWP...AND MODIFIED RUC SOUNDINGS.  PRIND 0-1 KM SRH
   OF AT LEAST 250-300 J/KG WILL CONTINUE OVER REGION BENEATH 40-50 KT
   LLJ PRESENTLY OBSERVED.  LLJ ALSO SHOULD STRENGTHEN SOMEWHAT AFTER
   ABOUT 2Z AS BOUNDARY LAYER DECOUPLES.  THIS DECOUPLING WILL BE
   GRADUAL ENOUGH TO KEEP EFFECTIVE INFLOW PARCELS ROOTED AT OR VERY
   NEAR SFC AND HELP TO MAINTAIN THREAT FOR DAMAGING GUSTS AND
   TORNADOES...AS WELL AS LARGE HAIL.
   
   ..EDWARDS.. 04/25/2007
   
   
   ATTN...WFO...LZK...SGF...SHV...TSA...FWD...
   
   32159502 31879665 31989774 32259840 32559828 32939726
   33659570 34319453 35489426 36849439 36819329 34849328
   33879298