MESOSCALE DISCUSSION 0823
   NWS STORM PREDICTION CENTER NORMAN OK
   0258 AM CDT FRI MAY 20 2011
   
   AREAS AFFECTED...SOUTHWEST/WEST-CENTRAL/WESTERN NORTH TX INTO
   WESTERN OK
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 311...
   
   VALID 200758Z - 200930Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 311
   CONTINUES.
   
   SEVERE TSTM WATCH 311 CONTINUES UNTIL 11Z. ISOLATED DAMAGING
   WINDS/SEVERE HAIL REMAIN A CONCERN IN ADDITION TO VERY HEAVY
   RAINFALL. MONITORING PORTIONS OF WESTERN/CENTRAL OK FOR THE
   POSSIBILITY OF AN ADDITIONAL WATCH.
   
   AN EXTENSIVE SQUALL LINE HAS EVOLVED ACROSS WEST-CENTRAL/WESTERN
   PART OF NORTH TX INTO SOUTHWEST OK OVERNIGHT...EXTENDING FROM NEAR
   I-20 EAST OF BIG SPRINGS TX INTO SOUTHWEST OK INCLUDING THE
   ALTUS/CLINTON AREAS AND I-40 VICINITY AS OF 0745Z. WHILE MEAN FLOW
   WILL REMAIN LARGELY ORIENTED PARALLEL TO THE ONGOING SQUALL LINE
   /FAVORABLE FOR CONTINUED LOCALLY HEAVY RAINFALL/...ISOLATED DAMAGING
   WINDS CANNOT BE RULED OUT AS SMALL SCALE BOWS EVOLVE...EVEN AMID
   CONSIDERABLE LOW LEVEL CINH. THE AIRMASS REMAINS RELATIVELY MORE
   STABLE WITH NORTHWARD EXTENT ACROSS WESTERN OK TO THE NORTH OF
   EARLIER EVENING OUTFLOW...BUT AN ISOLATED DAMAGING WIND THREAT MAY
   BE POSSIBLE NONETHELESS. ALONG THOSE LINES...A 49 KT MEASURED GUST
   WAS RECENTLY NOTED IN HOBART OK.
   
   HEAVY RAINFALL/ISOLATED DAMAGING WINDS ASIDE...THE REMAINING SEVERE
   HAIL POTENTIAL WILL LIKELY BE FOCUSED ACROSS SOUTHWEST TX...WHERE A
   MORE DISCRETE CONVECTIVE MODE EXISTS ON THE SOUTHERN PERIPHERY OF
   THE SQUALL LINE COINCIDENT WITH A RELATIVELY STRONGER RESERVOIR OF
   INSTABILITY/LAPSE RATES ALOFT.
   
   ..GUYER.. 05/20/2011
   
   
   ATTN...WFO...OUN...SJT...LUB...MAF...
   
   LAT...LON   30880107 30750215 31990164 33760012 35329901 34469830
               32040020 30880107