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    Day 2 Outlook >
Dec 2, 2016 1300 UTC Day 1 Convective Outlook
Updated: Fri Dec 2 12:52:55 UTC 2016 (Print Version | 20161202 1300Z Day 1 shapefile | 20161202 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 021252

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0652 AM CST FRI DEC 02 2016

   VALID 021300Z - 031200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER PARTS OF SOUTH TEXAS...

   ...SUMMARY...
   ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS PORTIONS OF SOUTH
   TEXAS THIS AFTERNOON INTO TONIGHT.

   ...SYNOPSIS...
   AN UPPER-AIR PATTERN TRANSITION IS UNDERWAY OVER THE CONTIGUOUS U.S.
   AS THE BIG CYCLONE OVER QUEBEC DEPARTS...AND A SYNOPTIC-SCALE TROUGH
   BECOMES EVEN BETTER-ESTABLISHED OVER THE WEST AND NORTHERN MEXICO. 
   THE MAJOR PLAYER IN THAT PROCESS IS A STRONG...BASAL SHORTWAVE
   PERTURBATION...NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY EXTENDING FROM
   A LOW OVER INLAND SOUTHERN CALIFORNIA SOUTH-SOUTHEASTWARD OVER BAJA
   AND THE GULF OF CALIFORNIA.  THAT LOW WILL DIG SOUTHEASTWARD ACROSS
   COASTAL SONORA THROUGH THE PERIOD...WITH HEIGHT FALLS REACHING
   SOUTHWEST TEXAS LATE TONIGHT.

   THE 11Z SURFACE ANALYSIS SHOWED A COLD FRONT FROM THE ATLANTIC...
   NORTHEAST OF THE BAHAMAS...WEST-SOUTHWESTWARD ACROSS SOUTH FLORIDA...
   BECOMING QUASISTATIONARY OVER THE GULF WESTWARD TO PADRE ISLAND AND
   THE LOWEST PART OF THE RIO GRANDE VALLEY.  THIS FRONT SHOULD DRIFT
   NORTHWARD ACROSS SOUTH TEXAS AND NORTHEASTERN MEXICO THROUGH THE
   PERIOD.  AS THE UPPER CYCLONE INFLUENCE ON LOW-LEVEL MASS FIELDS
   STRENGTHENS OVERNIGHT...A WEAK LEE-SIDE LOW SHOULD DEVELOP OVER
   NORTHEASTERN MEXICO...BETWEEN MONTERREY AND THE RIO GRANDE.

   ...SOUTH TEXAS...
   ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGH THIS AFTERNOON ON EITHER
   SIDE OF BOTH THE FRONT AND THE RIO GRANDE.  COVERAGE WILL BE LIMITED
   DIURNALLY BY WEAKNESS OF LIFT...AND BY A MODEST INVERSION APPARENT IN
   12Z CRP/BRO RAOBS.  CONVECTION SHOULD INCREASE THIS AFTERNOON AND
   ESPECIALLY INTO EVENING FROM A COMBINATION OF FRONTAL LIFT...WARM
   ADVECTION...AND IN MEXICO...UPSLOPE EFFECTS FROM THE EASTERLY
   BOUNDARY-LAYER FLOW COMPONENT NORTH OF THE FRONT.  MEXICAN
   CONVECTION MAY MOVE NORTHEASTWARD OVER SOUTH TEXAS.

   OVERNIGHT...AS THE NORTHWESTERN MEXICAN LOW STARTS TO CURVE CLOSER...
   AND THE INLAND BOUNDARY LAYER DECOUPLES...THE SOUTHERLY LLJ WILL
   INCREASE IN MAGNITUDE (TO 40-45 KT) AND BREADTH (WEST-CENTRAL TEXAS
   TO SOUTHWESTERN LOUISIANA).  ASSOCIATED LOW-LEVEL WARM ADVECTION AND
   MOISTURE TRANSPORT WILL INCREASE BOTH LOW-LEVEL THETA-E ABOVE THE
   FRONTAL SLOPE AND DEEP-LAYER LAPSE RATES...IN TURN STRENGTHENING
   BUOYANCY FOR PARCELS ISENTROPICALLY LIFTED TO THEIR LFC.  ELEVATED
   MUCAPE NEAR 500 J/KG SHOULD DEVELOP IMMEDIATELY POLEWARD OF THE
   FRONT...DECREASING TO AROUND 100 J/KG NEAR THE NORTH EDGE OF THE
   THUNDER OUTLOOK.  THIS SHOULD YIELD A NET EXPANSION OF OVERALL
   CONVECTIVE POTENTIAL -- AGAIN MOSTLY ELEVATED IN CHARACTER...WITH A
   CONDITIONAL EXCEPTION FOR A FEW SURFACE-BASED STORMS ALONG THE FRONT
   OR IN THE PROXIMAL WARM SECTOR.

   ANY SURFACE-BASED/WARM-SECTOR CONVECTION WOULD POSE A MARGINAL RISK
   FOR ALL SEVERE HAZARDS...GIVEN THE POTENTIAL FOR SUPERCELLULAR
   CHARACTER AMIDST ROUGHLY 1000 J/KG MLCAPE...50 KT EFFECTIVE-SHEAR
   MAGNITUDE...AND AROUND 150 J/KG EFFECTIVE SRH.  LACK OF MORE
   SUBSTANTIAL MID/UPPER-LEVEL FORCING AND WARM-SECTOR LOW-LEVEL LIFT
   EACH PRECLUDE GREATER SEVERE PROBABILITIES AT THIS TIME.

   ..EDWARDS/LEITMAN.. 12/02/2016

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z

        
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