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    Day 2 Outlook >
Dec 5, 2016 1300 UTC Day 1 Convective Outlook
Updated: Mon Dec 5 12:52:09 UTC 2016 (Print Version | 20161205 1300Z Day 1 shapefile | 20161205 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 051252

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0652 AM CST MON DEC 05 2016

   VALID 051300Z - 061200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM SOUTHEASTERN LOUISIANA TO
   SOUTHWESTERN GEORGIA AND THE CENTRAL FLORIDA PANHANDLE...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
   FROM SOUTHERN LOUISIANA TO NORTH-CENTRAL ALABAMA AND THE
   JACKSONVILLE...FL AREA...

   ...SUMMARY...
   A FEW STRONG TO SEVERE STORMS WITH POTENTIAL FOR DAMAGING WINDS AND
   A COUPLE TORNADOES ARE POSSIBLE THIS AFTERNOON INTO TONIGHT OVER
   PARTS OF THE SOUTHEAST.

   ...SYNOPSIS...
   IN MID/UPPER LEVELS...A LONGWAVE TROUGH OVER WESTERN TO CENTRAL NORTH
   AMERICA WILL SUPPORT BROADLY CYCLONIC FLOW FROM THE PACIFIC COAST TO
   THE APPALACHIANS BY THE END OF THE PERIOD.  AS THAT TROUGH DEEPENS...
   A SOUTHERN-STREAM 500-MB LOW -- NOW APPARENT IN MOISTURE-CHANNEL
   IMAGERY OVER MEXICO SOUTH OF THE TEXAS BIG BEND -- WILL EJECT
   NORTHEASTWARD.  THE ASSOCIATED PERTURBATION...EVEN WITH SOME EXPECTED
   DEAMPLIFICATION...WILL REMAIN STRONG AS IT REACHES THE SABINE RIVER
   AREA BY 00Z...THEN THE APPALACHIANS OF EASTERN TENNESSEE AND NORTHERN
   GEORGIA BY 12Z.  

   THE ASSOCIATED SURFACE LOW WAS ANALYZED AT 11Z OVER THE NORTHWESTERN
   GULF...OFFSHORE FROM THE MIDDLE TEXAS COAST.  THIS LOW SHOULD MIGRATE
   TO SOUTHWESTERN LOUISIANA BY 00Z AND MIDDLE TENNESSEE NEAR 12Z.  AN
   ACCOMPANYING COLD FRONT WILL PROGRESS EASTWARD TO SOUTHEASTWARD
   ACROSS THE NORTHWESTERN GULF AND LOWER DELTA REGION...REACHING
   ALABAMA AND PERHAPS THE WESTERNMOST FLORIDA PANHANDLE BY 12Z.  A
   CONVECTIVELY REINFORCED WARM-FRONTAL ZONE WAS DRAWN AT 11Z FROM THE
   LOW EAST-NORTHEASTWARD OVER THE MISSISSIPPI RIVER MOUTH...OFFSHORE
   MISSISSIPPI AND ALABAMA TO THE WESTERN FLORIDA PANHANDLE AND
   SOUTHERN GEORGIA.  THIS BOUNDARY SHOULD MOVE IRREGULARLY
   NORTHEASTWARD AT LEAST TO SOUTH-CENTRAL ALABAMA AND SOUTHERN/CENTRAL
   GEORGIA OVERNIGHT...AHEAD OF THE COLD FRONT. 

   ...LOWER MISSISSIPPI VALLEY...CENTRAL GULF COAST TO GEORGIA...
   AT LEAST A COUPLE OF BANDS OF SCATTERED THUNDERSTORMS SHOULD DEVELOP
   OVER THE GULF AND MOVE NORTHEASTWARD OVER THE REGION THROUGH THE
   PERIOD...OFFERING A RISK OF DAMAGING GUSTS.  A SLIGHT RISK OF
   TORNADOES ALSO EXISTS...PRIMARILY ON THE CENTRAL COASTAL PLAIN WHERE
   THE GREATEST POTENTIAL EXISTS FOR DISCRETE OR EMBEDDED SUPERCELLS
   AND QLCS MESOVORTICES TO ACCESS SURFACE PARCELS...WHILE REMAINING IN
   A VERY MOISTURE-RICH...LOW-LCL AND HIGH-HELICITY ENVIRONMENT NEAR THE
   WARM FRONT.  MLCAPE 500-800 J/KG IS EXPECTED OVER INLAND AREAS ALONG
   AND SOUTH OF THAT FRONT AND AHEAD OF THE PRE-COLD-FRONTAL CONVECTIVE
   BAND. 

   WITH THE NORTHEASTWARD EJECTION OF THE MEXICAN MIDDLE/UPPER-LEVEL
   CYCLONE...DEEP SHEAR IS EXPECTED TO STRENGTHEN THROUGH THE EVENING
   HOURS OVER THAT PORTION OF THE WARM SECTOR OCCUPYING THE NORTHERN
   GULF AND ADJACENT COAST...ALBEIT WITH A STRONG COMPONENT OF THE
   MEAN-WIND AND DEEP-SHEAR VECTORS PARALLEL TO BANDS OF LOW-LEVEL
   CONVECTIVE FORCING.  LOW-LEVEL HODOGRAPHS AND VORTICITY WILL BE
   MAXIMIZED ALONG AND NORTH OF THE WARM-FRONTAL ZONE.  THAT WILL LEAD
   TO A NARROW FRONTAL CORRIDOR OF MOST FAVORABLE SHEAR/BUOYANCY
   JUXTAPOSITION FOR MESOCYCLONE INTENSIFICATION...BUT ALIGNED
   SUBSTANTIALLY ORTHOGONAL TO THE CELL-MOTION VECTOR. 

   CONSIDERABLE UNCERTAINTY REMAINS REGARDING THE INLAND PENETRATION OF
   THAT FRONTAL ZONE...GIVEN THE POTENTIAL FOR EPISODIC AREAS OF BOTH
   CONVECTIVE AND STRATIFORM PRECIP TO DEVELOP TO ITS NORTH AND HINDER
   POLEWARD PROGRESS OF THE BOUNDARY.  THE MOST AGGRESSIVE SCENARIOS
   WITH BOTH WARM ADVECTION COMBINED WITH LEAST AGGRESSIVE ON
   COLD-SECTOR PRECIP WOULD EXTEND WEAKLY TO NEUTRALLY UNSTABLE
   NEAR-SURFACE PARCELS NORTH OF THE BOUNDARY INTO SOUTH-CENTRAL
   ALABAMA...WHILE THE BULK OF THE GUIDANCE REMAINS CLOSER TO THE COAST.
    THIS IN TURN LEADS TO UNCERTAIN INLAND EXTENT/TIMING OF
   SURFACE-BASED EFFECTIVE-INFLOW PARCELS OF AT LEAST NEUTRAL TO WEAK
   0-1-KM INSTABILITY...ACCOUNTING FOR THE BROAD-BRUSHED SHAPE AND
   NORTHWARD RAMP-DOWN OF SEVERE PROBABILITIES IN THIS OUTLOOK. 

   THUNDERSTORMS WILL BE COMMON NORTH OF THE WARM FRONT IN AN ELEVATED
   WARM-ADVECTION AND MOISTURE-TRANSPORT CONVEYOR.  HOWEVER...THE LACK
   OF MORE ROBUST LAPSE RATES AND BUOYANCY...ALONG WITH THE DENSE AND
   MESSY CONVECTIVE MODES LIKELY IN THAT REGIME...INDICATE AGAINST A
   SUBSTANTIAL HAIL THREAT.  SEVERE WIND BECOMES LESS PROBABLE INLAND
   FROM THE WARM FRONT AS WELL...AS THE BOUNDARY LAYER DEEPENS AND
   BECOMES MORE STABLE WITH NORTHWARD EXTENT.

   ..EDWARDS/LEITMAN.. 12/05/2016

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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