Apr 13, 2007 1300 UTC Day 1 Convective Outlook
Updated: Fri Apr 13 12:38:10 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the southern plains later today and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20070413 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20070413 1300 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20070413 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20070413 1300 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 131233
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0733 AM CDT FRI APR 13 2007
   
   VALID 131300Z - 141200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
   TONIGHT FROM CENTRAL/NE TX INTO NW LA AND EXTREME SW AR...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK...FROM
   CENTRAL TX AND SRN OK EWD TO THE LOWER MS VALLEY...
   
   ...SYNOPSIS...
   A STRONG MID LEVEL TROUGH OVER SE AZ HAS NOW TURNED TO THE E AND
   WILL CONTINUE EWD OVER SRN NM THE FIRST PART OF THE DAY...AND THEN
   NEWD OVER NW TX AND OK BY TONIGHT.  AN ASSOCIATED SURFACE LOW INVOF
   THE TX/NM BORDER WILL DEVELOP EWD ACROSS NW INTO N CENTRAL TX BY
   THIS EVENING...AND THEN CONTINUE TO THE ENE OVER SRN AR TONIGHT.  A
   MOIST WARM SECTOR /BOUNDARY LAYER DEWPOINTS OF 65-70 F/ NOW ACROSS S
   TX WILL SPREAD NWD INTO N CENTRAL AND NE TX BY MID-LATE AFTERNOON AS
   A RESULT OF ADVECTION ON A 40 KT SLY LLJ IN ADVANCE OF THE SURFACE
   LOW AND MID LEVEL WAVE...AND VERTICAL MIXING WITH DAYTIME HEATING. 
   THE INCREASING LOW-LEVEL MOISTURE WILL CONTRIBUTE TO SUBSTANTIAL
   DESTABILIZATION ACROSS CENTRAL AND E TX...WHILE VERTICAL SHEAR WILL
   BECOME QUITE FAVORABLE FOR SUPERCELLS IN THE WARM SECTOR.
   
   ...CENTRAL/NE TX TODAY EWD ACROSS SRN AR AND NRN LA TONIGHT...
   ONE CONCERN TODAY WILL BE THE EXTENT OF ELEVATED CONVECTION ACROSS
   N/NE TX...WHERE RAINFALL AND EVAPORATIVE COOLING WITHIN THE
   INITIALLY DRIER BOUNDARY LAYER COULD TEND TO LIMIT THE NWD EXTENT OF
   THE UNSTABLE WARM SECTOR.  HOWEVER...CONSENSUS OF SHORT RANGE MODELS
   SUGGESTS THAT THE MAJORITY OF CONVECTION FROM THIS MORNING INTO MID
   AFTERNOON SHOULD BE NEAR AND N OF THE RED RIVER WHERE ASCENT WILL BE
   FOCUSED N OF THE DEEP BAROCLINIC ZONE.  THEREFORE...MODERATE
   INSTABILITY WILL LIKELY DEVELOP IN THE WARM SECTOR ROUGHLY ALONG AND
   S OF A LINE FROM THE DFW METROPLEX TO THE TXK-SHV AREA BY THIS
   EVENING.
   
   VERTICAL SHEAR PROFILES ARE FORECAST TO BECOME QUITE FAVORABLE FOR
   TORNADIC SUPERCELLS IN ADVANCE OF THE SURFACE LOW AND EWD ALONG AND
   EVEN S OF THE WARM FRONT INTO E/NE TX.  A FEW DISCRETE SUPERCELLS
   WILL LIKELY DEVELOP ALONG THE DRYLINE AND PERHAPS IN THE OPEN WARM
   SECTOR BY MID AFTERNOON AND MOVE ENEWD INTO THE REGION OF STRONGER
   LOW-LEVEL SHEAR.  BOUNDARY LAYER DEWPOINTS IN THE MID-UPPER 60S AND
   LARGE HODOGRAPHS WITH EFFECTIVE SRH OF 400-500 M2/S2 APPEAR
   SUPPORTIVE OF SUPERCELLS WITH STRONG TORNADOES LATE THIS AFTERNOON
   INTO THIS EVENING ACROSS NE TX.  
   
   BY TONIGHT...CONVECTION SHOULD TEND TOWARD A MORE LINEAR STRUCTURE
   AS THE DEEP LAYER SHEAR AND BOUNDARY ORIENTATIONS BECOME MORE
   PARALLEL /SW TO NE/.  THE NET RESULT WILL BE A TRANSITION TO MORE OF
   A DAMAGING WIND THREAT ACROSS LA...THOUGH VERTICAL SHEAR WILL STILL
   FAVOR A FEW EMBEDDED MESOCYCLONES/LEWPS WITHIN THE BAND OF
   STORMS...AND AN ASSOCIATED THREAT FOR A FEW TORNADOES OVERNIGHT.
   
   ...NW TX AND SRN OK TODAY...
   A LARGE CLUSTER OF ELEVATED THUNDERSTORMS IS DEVELOPING FROM NW TX
   INTO CENTRAL OK IN ASSOCIATION WITH INCREASINGLY MOIST WAA AND A
   LEAD SHORTWAVE TROUGH EJECTING NEWD IN ADVANCE OF THE MAIN WAVE OVER
   AZ/NM.  MUCAPE OF 750-1250 J/KG BASED IN THE 800-700 MB LAYER AND
   STEEP MID LEVEL LAPSE RATES WILL SUPPORT A FEW STORMS WITH LARGE
   HAIL THROUGH THE DAY SPREADING EWD OVER SRN OK AND ADJACENT RED
   RIVER COUNTIES IN N TX.
   
   ..THOMPSON/CROSBIE.. 04/13/2007
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z