Apr 22, 2011 1300 UTC Day 1 Convective Outlook
Updated: Fri Apr 22 12:58:07 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110422 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110422 1300 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20110422 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20110422 1300 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
   SPC AC 221253
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0753 AM CDT FRI APR 22 2011
   
   VALID 221300Z - 231200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS MAINLY THIS AFTERNOON INTO
   TONIGHT FROM THE SRN PLAINS TO THE OH VALLEY...
   
   ...SYNOPSIS...
   A WELL-DEFINED MIDLEVEL SHORTWAVE TROUGH EMERGING OVER WRN NEB/SD
   THIS MORNING WILL MOVE EWD/ENEWD TOWARD MI AND STRENGTHEN THROUGH
   TONIGHT...WHILE A REMNANT LEE CYCLONE IN CENTRAL KS DEVELOPS NEWD IN
   ADVANCE OF THE MIDLEVEL TROUGH.  THE SURFACE WARM SECTOR AND ITS MID
   60S BOUNDARY LAYER DEWPOINTS WILL SURGE NEWD TODAY FROM OK/AR TO
   MO/IL TODAY IN CONJUNCTION WITH THE SURFACE LOW.
   
   ...MO/IL/INDIANA THROUGH TONIGHT...
   AN ONGOING MCS JUST N OF THE WARM FRONT IN NE KS/NW MO IS EXPECTED
   TO PERSIST INTO THE DAY WHILE PROGRESSING EWD OVER NRN MO INTO
   CENTRAL IL.  THIS CONVECTION WILL BE MAINTAINED BY WAA ON THE NOSE
   OF A SWLY LLJ...AND A FEED OF STEEP MIDLEVEL LAPSE RATES FROM THE
   WSW.  ISOLATED LARGE HAIL AND DAMAGING WINDS WILL BE POSSIBLE WITH
   THIS CONVECTION.
   
   IN THE WAKE OF THE MORNING WAA STORMS...THE BOUNDARY LAYER WILL
   WARM/MOISTEN NEWD FROM OK/AR INTO MO/IL...WHILE MIDLEVEL LAPSE RATES
   REMAIN STEEP.  THE STEEP LAPSE RATES WILL INITIALLY PROVIDE A
   CAP...BUT SURFACE HEATING/MIXING AND LOW-LEVEL ASCENT ALONG A SW-NE
   ORIENTED COLD FRONT /TRAILING THE SURFACE LOW/ SHOULD RESULT IN
   SURFACE-BASED THUNDERSTORM DEVELOPMENT BY LATE AFTERNOON FROM
   CENTRAL MO INTO ERN AND SRN OK.  STRONG INSTABILITY IS EXPECTED IN
   ADVANCE OF THE COLD FRONT...WITH AFTERNOON MLCAPE RANGING FROM
   2500-3500 J/KG IN SRN/ERN OK TO ROUGHLY 2000 J/KG IN PROXIMITY TO
   THE SURFACE LOW AND WARM FRONT IN MO/IL.  THIS
   INSTABILITY...COMBINED WITH 0-6 KM BULK SHEAR IN EXCESS OF 50
   KT...WILL SUPPORT A THREAT FOR ORGANIZED SEVERE STORMS...INCLUDING
   SUPERCELLS.
   
   CONVECTIVE MODE ALONG THE COLD FRONT IS OF SOME CONCERN...GIVEN
   DEEP-LAYER FLOW/SHEAR VECTORS SOMEWHAT PARALLEL TO THE BOUNDARY. 
   THE MOST PROBABLE SCENARIO APPEARS TO BE FOR SEMI-DISCRETE
   SUPERCELLS IN THE FIRST FEW HOURS AFTER INITIATION...WITH THE
   POTENTIAL TO PRODUCE VERY LARGE HAIL AND A FEW TORNADOES.  LOW-LEVEL
   SHEAR WILL BE MORE FAVORABLE FOR TORNADOES NEAR THE WARM FRONT INTO
   IL/INDIANA BY LATE AFTERNOON/EVENING...THOUGH SUFFICIENT LOW-LEVEL
   SHEAR /0-1 KM SRH OF 150-200 M2 PER S2/ IS STILL EXPECTED AHEAD OF
   THE COLD FRONT IN THE ZONE OF STRONGEST INSTABILITY INTO ERN OK. 
   LATER INTO THE EVENING...CONVECTION SHOULD TEND TO GROW UPSCALE INTO
   LINE SEGMENTS WITH AN ACCOMPANYING RISK FOR DAMAGING WINDS AS THE
   SYNOPTIC SYSTEM PROGRESSES EWD.  FARTHER W...CONVECTION COULD
   PERSIST WELL INTO THE OVERNIGHT HOURS ACROSS ERN OK AS THE SURFACE
   FRONT STALLS AND A LOW-LEVEL WAA REGIME DEVELOPS ALONG/N OF THE
   BOUNDARY.
   
   ...N CENTRAL AND CENTRAL TX LATE THIS AFTERNOON/EVENING...
   THE MORE WIDESPREAD CONVECTION IS EXPECTED TO REMAIN NE OF THE
   DRYLINE/COLD FRONT INTERSECTION ACROSS S CENTRAL OK. 
   HOWEVER...STRONG SURFACE HEATING ALONG THE DRYLINE COULD RESULT IN
   SUFFICIENT WEAKENING OF THE CAP TO ALLOW ISOLATED THUNDERSTORM
   DEVELOPMENT LATE THIS AFTERNOON/EVENING ACROSS CENTRAL/N CENTRAL TX.
   MLCAPE AOA 2000 J/KG AND 0-6 KM BULK SHEAR AOA 30 KT WILL BE AT
   LEAST MARGINALLY FAVORABLE FOR SUPERCELLS.  ISOLATED LARGE HAIL
   AND/OR DAMAGING GUSTS SHOULD BE THE PRIMARY SEVERE STORM THREATS
   GIVEN RELATIVELY WEAK LOW-LEVEL SHEAR AND A DEEP MIXED BOUNDARY
   LAYER.
   
   ..THOMPSON/COHEN.. 04/22/2011
   
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