Feb 21, 2013 0600 UTC Day 1 Convective Outlook
Updated: Thu Feb 21 05:55:30 UTC 2013
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20130221 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20130221 1200 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
20130221 1200 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
20130221 1200 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 210552
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1152 PM CST WED FEB 20 2013
   
   VALID 211200Z - 221200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM E-CNTRL TX EWD TO PARTS OF
   THE LOWER MS RIVER VALLEY...
   
   ...SYNOPSIS...
   A POTENT UPPER LOW WILL MOVE FROM THE SRN HIGH PLAINS TO IA DURING
   THE PERIOD AS THE PRIMARY UPPER FORCING FOR ASCENT MOVES FROM THE
   SRN PLAINS TO THE MIDWEST.  IN THE LOWER LEVELS...A WARM FRONTAL
   ZONE OVER CNTRL TX EWD INVOF THE UPPER TX AND LA COAST WILL MOVE NWD
   AHEAD OF WEAK SURFACE LOW FORECAST TO DEVELOP EWD FROM CNTRL TX TO
   THE LOWER MS RIVER VALLEY.  ASIDE FROM EARLY DAY ELEVATED
   THUNDERSTORMS POSING A LARGE HAIL RISK...THE PRIMARY SEVERE
   THUNDERSTORM RISK AREA WILL BE CONFINED TO THE WARM SECTOR NEAR AND
   S OF THE EWD MIGRATING LOW ACROSS THE LOWER MS RIVER VALLEY.
   
   ...E-CNTRL TX EWD TO THE LOWER MS RIVER VALLEY...
   SCTD ELEVATED STORMS OVER TX WILL PROBABLY BE ONGOING DURING THE
   MORNING HOURS OWING TO STRONG ISENTROPIC ASCENT.  THIS WILL OCCUR AS
   A MODIFIED MARITIME AIRMASS ADVANCES NWD UNDERNEATH THE NRN FRINGE
   OF A MEXICAN PLATEAU EMANATING EML.  THE MORE ROBUST UPDRAFTS WITH
   THIS ACTIVITY OVER TX WILL PROBABLY POSE AT LEAST SOME LARGE HAIL
   THREAT AS STRONG EFFECTIVE SHEAR COINCIDES WITH A STEEP LAPSE RATE
   PROFILE.  THE MORNING TSTM ACTIVITY MAY CONTINUE AS IT MOVES EWD
   INTO THE ARKLATEX AS THIS REGION IS INCREASINGLY INFLUENCED BY THE
   SRN EXTENT OF APPRECIABLE MID LEVEL HEIGHT FALLS.  
   
   MORE UNCERTAIN IS THE EVENTUAL EVOLUTION OF DIURNALLY ENHANCED
   ACTIVITY THAT ENCOUNTERS A SLOW-TO-DEPART SERN U.S. RIDGE OVER THE
   NRN GULF COAST STATES.  MODELS DIFFER REGARDING WHETHER AN ORGANIZED
   LINEAR BAND OF STORMS CAN BE SUSTAINED ACROSS THE ARKLATEX INTO THE
   LOWER MS VALLEY AS INSTABILITY BECOMES MORE LIMITED WITH EWD EXTENT
   OVER THE LOWER MS VALLEY.  ADDITIONALLY...IT REMAINS UNCLEAR ON THE
   COVERAGE OF PREFRONTAL STORMS THAT MAY DEVELOP ACROSS THE WARM
   SECTOR.  DESPITE THESE PREDICTABILITY CONCERNS...THE NWD ADVANCE OF
   A WARM FRONT THROUGH MUCH OF ERN TX...LA...AND SRN PORTIONS OF MS
   WILL FEATURE DEWPOINTS RISING INTO THE LOW-MID 60S AND SBCAPE
   INCREASING TO 250-750 J/KG ACCORDING TO MODEL SOUNDINGS.  STRONG
   DEEP SHEAR WILL SUPPORT ORGANIZED STORMS --INCLUDING
   SUPERCELLS--...AND A BELT OF 50+ KT H85 FLOW WILL LIKELY RESULT IN
   LARGE LOOPING HODOGRAPHS...WITH AN ATTENDANT CONDITIONAL TORNADO
   RISK.  BY THE LATE AFTERNOON-EVENING HOURS...MODELS SHOW A GRADUAL
   VEERING IN LOW LEVEL FLOW COINCIDENT WITH THE COLD FRONT BECOMING
   INCREASINGLY ORIENTED SW-NE AS THE MAIN BODY OF UPPER FORCING
   LARGELY DEPARTS THE REGION.  AS SUCH...THE ZONE OF THE STRONGEST
   STORMS AND REMAINING ISOLD SEVERE RISK WILL FOCUS OVER THE LOWER MS
   VALLEY DURING THE LATTER HALF OF THE PERIOD.
   
   ..SMITH/ROGERS.. 02/21/2013
   
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