Categorical Graphic
Probabilistic Tornado Graphic
Probabilistic Damaging Wind Graphic
Probabilistic Large Hail Graphic

   SPC AC 211255
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0755 AM CDT FRI MAY 21 2010
   
   VALID 211300Z - 221200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE LOWER OH
   VALLEY ACROSS THE TN VALLEY TO THE SOUTH AND SOUTHEAST...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM SERN WY AND ADJACENT AREAS
   OF SD AND NEB SOUTH ACROSS ERN CO AND THE SRN HIGH PLAINS...
   
   ...SYNOPSIS...
   MID LEVEL FLOW WILL REMAIN QUITE AMPLIFIED ACROSS THE CONUS INTO THE
   WEEKEND AS ONE WELL-DEFINED DISTURBANCE MOVES ACROSS THE MIDWEST
   THROUGH TODAY AND ANOTHER SUBSTANTIAL TROUGH DEEPENS OVER THE WEST
   AND ROCKIES. TRANSIENT RIDGING WILL MOVE FROM THE PLAINS TO THE MS
   VALLEY THIS PERIOD.
   
   ...CNTRL/SRN HIGH PLAINS...
   ANOTHER STRONG SHORT WAVE TROUGH COMING ACROSS THE CA/ORE COAST THIS
   MORNING WILL ROTATE THROUGH THE LARGER-SCALE TROUGH ESTABLISHED
   ACROSS THE WEST THROUGH TONIGHT. MID LEVEL SWLY FLOW IS FORECAST TO
   STRENGTHEN ACROSS ROCKIES AND ADJACENT HIGH PLAINS THROUGH THIS
   AFTERNOON AS LEE CYCLOGENESIS OCCURS OVER WY/CO. LOW LEVEL MOISTURE
   ...CURRENTLY MARGINAL FOR DEEP CONVECTION...WILL INCREASE NWWD AS
   PRESSURE FALLS COMMENCE IN EARNEST LATER THIS MORNING AND LOW LEVEL
   SELY FLOW STRENGTHENS. COMBINED WITH BOUNDARY LAYER HEATING AND
   STEEPENING LAPSE RATES ALOFT...EXPECT A GENERALLY N-S AXIS OF
   INSTABILITY TO DEVELOP WITH MLCAPE VALUES RANGING FROM ABOUT 500
   J/KG ACROSS SERN WY...TO AS HIGH AS 2000 J/KG OVER PARTS OF TX.
   
   LACK OF STRONGER DESTABILIZATION WITH NWWD EXTENT WILL MOST LIKELY
   BE COMPENSATED FOR BY STRONG DYNAMIC FORCING FOR ASCENT WITH THE
   APPROACHING SHORT WAVE...AS WELL AS OROGRAPHIC/UPSLOPE FLOW. THESE
   INFLUENCES WILL LEAD TO THUNDERSTORM DEVELOPMENT...FIRST OVER THE
   HIGHER TERRAIN TO THE WEST...AND THEN SPREADING EAST INTO AXIS OF
   MODEST INSTABILITY FROM SERN WY ACROSS NERN CO. PRONOUNCED SPEED
   SHEAR...AS WELL AS STRONG DIRECTIONAL SHEAR LOWER IN THE STORM
   UPDRAFT WILL LEAD TO ROTATING CELLS CAPABLE OF VERY LARGE HAIL AND
   PERHAPS A COUPLE OF TORNADOES.
   
   FARTHER SOUTH ALONG THE DRY LINE...FROM SERN CO TO WEST TX/ERN
   NM...STORM INITIATION BECOMES MORE UNCERTAIN. LACK OF STRONGER
   HEIGHT FALLS/FORCING AND DEGREE OF CONVECTIVE INHIBITION SUGGEST
   THAT STORM DEVELOPMENT WILL BE ISOLATED ALONG THIS AXIS. CONSENSUS
   EXISTS AMONG HIGH RESOLUTION MODELS AND THE NAM THAT SURFACE HEATING
   AND WEAK BACKGROUND ASCENT MAY BE ADEQUATE FOR AT LEAST A COUPLE OF
   STORMS TO INITIATE...ESPECIALLY FROM TX PNHDL SOUTH TO NEAR THE
   PECOS RIVER. SHEAR PROFILES WILL BE SUPPORTIVE OF SUPERCELLS AND
   LARGE HAIL SHOULD BE THE PRIMARY HAZARD FROM THIS ACTIVITY THAT MAY
   DECAY RATHER QUICKLY AFTER DARK.
   
   ...SOUTH...
   A CORRIDOR OF STRONG HEATING WILL OCCUR ALONG AND SOUTH OF THE
   DIFFERENTIAL HEATING ZONE BECOMING ESTABLISHED FROM SRN MS TO SRN GA
   AND NORTH FL THIS MORNING. VERY MOIST AIR MASS IN THIS ZONE WILL
   CONTRIBUTE TO THE DEVELOPMENT OF STRONG INSTABILITY AND WEAK
   INHIBITION. WHILE STRONGER FORCING WITH THE MIDWEST UPPER TROUGH
   REMAINS NORTH OF THIS AREA...MID LEVEL WLY FLOW OF 20-30 KT WILL BE
   SUFFICIENT FOR SOME STORM ORGANIZATION AND PERHAPS EVEN SUPERCELLS
   AS CONVECTION INCREASES THROUGH THE AFTERNOON. LARGE HAIL AND HIGH
   WINDS SHOULD BE THE PRIMARY HAZARDS.
   
   THERE IS GREATER UNCERTAINTY OF STORM COVERAGE AND INTENSITY NWD
   ACROSS THE TN VALLEY WHERE AIR MASS WILL TAKE LONGER TO RECOVER FROM
   MORNING CONVECTION AND CLOUDS. SHEAR WILL BE STRONGER IN THIS REGION
   AND EXPECT GREATEST CHANCE FOR STRONG TO SEVERE STORMS MAY BE LATE
   AFTERNOON INTO THE EVENING AS LIFT WITH THE COLD FRONT MOVES INTO
   THIS AREA FROM THE NORTHWEST.
   
   ...MIDWEST...
   SOME WEAK DESTABILIZATION AND PERSISTENT BACKGROUND SYNOPTIC SALE
   ASCENT APPEARS LIKELY AS UPPER TROUGH SWINGS ACROSS THIS REGION
   THROUGH THE DAY. THIS SHOULD CONTRIBUTE TO ONE OR TWO BANDS OF 
   THUNDERSTORMS SPREADING ACROSS THE REGION FROM ERN IL TO OH. SHEAR
   PROFILES ARE NOT PARTICULARLY FAVORABLE FOR SEVERE STORMS.
   HOWEVER...COLD AIR ALOFT AND CYCLONIC FLOW REGIME DO SUGGEST THAT A
   FEW OF THE STRONGER STORMS MAY BE ACCOMPANIED BY HAIL AND PERHAPS
   EVEN A BRIEF TORNADO.
   
   ..CARBIN/ROGERS.. 05/21/2010
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z