SPC AC 121936

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0136 PM CST SAT DEC 12 2015

   VALID 122000Z - 131200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE SRN
   PLAINS...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM TX INTO ERN KS...

   ...SUMMARY...
   ISOLATED SEVERE THUNDERSTORMS ARE EXPECTED TO AFFECT PORTIONS OF THE
   CENTRAL AND SOUTHERN PLAINS LATER THIS AFTERNOON THROUGH TONIGHT. 
   WHILE DAMAGING STRAIGHT-LINE WINDS WILL BE THE PRIMARY HAZARD...A
   COUPLE TORNADOES AND MARGINALLY SEVERE HAIL ARE ALSO POSSIBLE.

   NO CHANGES WERE MADE TO THE PREVIOUS OUTLOOK. STORMS ARE STILL
   EXPECTED TO FORM LATER TODAY ACROSS E TX WITHIN A DEVELOPING MOIST
   CONFLUENCE ZONE AND AIDED BY A LEADING UPPER DISTURBANCE...AND
   ACROSS WRN TX ALONG A DEVELOPING COLD FRONT. LOCALLY DAMAGING WINDS
   AND MARGINAL HAIL WILL BE THE MAIN THREATS WITH THE WRN
   ACTIVITY...WITH PERHAPS A WEAK/BRIEF TORNADO ACROSS ERN TX.

   ..JEWELL.. 12/12/2015

   .PREV DISCUSSION... /ISSUED 1025 AM CST SAT DEC 12 2015/

   ...SRN PLAINS THIS EVENING THROUGH EARLY SUNDAY...
   A DEEP MIDLEVEL TROUGH OVER AZ THIS MORNING WILL PROGRESS EWD TO THE
   SRN HIGH PLAINS TONIGHT...AS AN ASSOCIATED SURFACE CYCLONE IN
   CENTRAL NM DEVELOPS ENEWD AND DEEPENS ALONG A PRE-EXISTING FRONT
   NEAR THE KS/OK BORDER BY 12Z SUNDAY.  AN ACCOMPANYING COLD FRONT
   WILL SURGE EWD ACROSS W TX THIS EVENING AND REACH AREAS E OF THE
   I-35 CORRIDOR IN TX/OK BY SUNDAY MORNING.  IN ADVANCE OF THE
   DEEPENING CYCLONE...LOW-LEVEL MOISTURE CONTINUES TO SPREAD NWD
   ACROSS TX/OK...WHERE BOUNDARY LAYER DEWPOINTS NOW RANGE FROM THE LOW
   60S IN OK /MEAN MIXING RATIOS NEAR 11 G PER KG/ TO THE LOW 70S IN S
   TX /MEAN MIXING RATIOS NEAR 15 G PER KG/. SURFACE HEATING WILL BE
   MUTED BY THICK CLOUD COVER OVER MOST OF THE SRN PLAINS.  MIDLEVEL
   LAPSE RATES WILL NOT BE PARTICULARLY STEEP...AND LAPSE RATES ABOVE
   THE 500 MB LEVEL WILL BE POOR WITHIN THE SUBTROPICAL CIRRUS PLUME. 
   THE NET RESULT WILL BE ONLY A MODEST DIURNAL INCREASE IN BUOYANCY
   FROM TX INTO OK.

   THERE WILL BE A COUPLE OF POSSIBILITIES FOR STORM INITIATION LATER
   THIS AFTERNOON.  ONE MAY EVOLVE WITHIN A CONFLUENCE BAND ALONG THE
   MOIST AXIS FROM THE EXTREME NW GULF INTO SE AND E TX...IN
   ASSOCIATION WITH A LEAD SHORTWAVE TROUGH.  THE INFLUENCE OF THE LEAD
   WAVE WILL ALSO EXTEND NWD INTO OK.  THE STRONGEST STORMS WITHIN THIS
   REGIME SHOULD BE IN CLOSER PROXIMITY TO THE WARMER/MOISTURE BOUNDARY
   LAYER NEAR THE MIDDLE TX COAST.  THERE WILL BE A CONDITIONAL
   SUPERCELL RISK WITH ANY SUFFICIENTLY DEEP UPDRAFTS IN THIS
   BAND...BUT DETAILS OF STORM EVOLUTION AND ANY ASSOCIATED TORNADO OR
   WIND DAMAGE RISK REMAIN UNCERTAIN.  LATER THIS EVENING...A FEW
   STORMS MAY FORM ALONG THE STALLED FRONT ACROSS W/NW OK.  A SUPERCELL
   OR TWO WILL BE POSSIBLE GIVEN MLCAPE OF 500-750 J/KG AND EFFECTIVE
   BULK SHEAR NEAR 40 KT...BUT THE OVERALL SEVERE RISK IS TEMPERED BY
   QUESTIONS ABOUT THE DEGREE OF SURFACE HEATING AND WHETHER OR NOT ANY
   STORMS WILL MOVE ALONG THE FRONT OR CROSS TOO QUICKLY INTO THE COLD
   AIR.

   THE PRIMARY RISK IS EXPECTED TO BEGIN THIS EVENING ACROSS W TX AS
   THE PAC FRONT AND BAND OF ASCENT BEGIN TO INTERACT WITH THE W EDGE
   OF THE MOIST SECTOR.  RELATIVELY QUICK SQUALL LINE FORMATION IS
   EXPECTED AND THE STORMS WILL SURGE EWD OVERNIGHT WITH THE FRONT.  A
   FEW DAMAGING WIND GUSTS WILL BE THE MAIN CONCERN OVERNIGHT.

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