Dec 25, 2012 0600 UTC Day 1 Convective Outlook
Updated: Tue Dec 25 06:04:37 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20121225 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20121225 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
20121225 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
20121225 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 250600
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1200 AM CST TUE DEC 25 2012
   
   VALID 251200Z - 261200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS SOUTHEAST TX AND PORTIONS
   OF LA/MS/AL/FL PANHANDLE...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE GULF COAST/SOUTHEAST
   STATES...
   
   ...A DANGEROUS CHRISTMAS DAY/NIGHT SEVERE WEATHER EPISODE IS LIKELY
   TO UNFOLD...INCLUDING THE POTENTIAL FOR STRONG TORNADOES AND
   WIDESPREAD DAMAGING WINDS...ACROSS PORTIONS OF THE GULF COAST REGION
   AND LOWER MS RIVER VALLEY...
   
   ...SYNOPSIS...
   A PROGRESSIVE LARGE SCALE FLOW PATTERN WILL PREVAIL OVER THE CONUS
   DURING THE PERIOD. THE PRIMARY SYSTEM OF FOCUS WITH RESPECT TO DEEP
   CONVECTION WILL BE A VIGOROUS SHORTWAVE TROUGH /AND ASSOCIATED
   STRONG UPPER JET STREAK/ AS IT SPREADS EASTWARD...AMPLIFIES...AND
   THEN BECOMES INCREASINGLY CLOSED/NEGATIVELY TILTED TONIGHT AS IT
   ADVANCES FROM THE SOUTHERN PLAINS TO THE LOWER MS VALLEY/TN VALLEY.
   
   ...GULF COAST REGION/LOWER MS VALLEY TO SOUTHEAST STATES...
   GIVEN THE LARGE SCALE SCENARIO AS PREVIOUSLY DESCRIBED...A SURFACE
   LOW IS EXPECTED TO STEADILY DEEPEN AS IT SPREADS NORTHEASTWARD FROM
   SOUTHEAST TX THIS MORNING TO THE TN VALLEY TONIGHT. AS THIS
   OCCURS...AN INCREASINGLY MOIST LOW-LEVEL AIRMASS WILL DEVELOP
   NORTHWARD IN TANDEM WITH A WEST-EAST ORIENTED WARM FRONT...WITH
   LOWER 60S DEWPOINTS /AND SOME MIDDLE 60S F NEAR THE COAST/ BECOMING
   INCREASINGLY PREVALENT WITHIN THE WARM SECTOR.
   
   INITIALLY...STRONG/POTENTIALLY SEVERE TSTMS ARE EXPECTED TO BE
   ONGOING THIS MORNING...ESPECIALLY ACROSS SOUTHEAST TX INTO LA. THIS
   INCLUDES THE POSSIBILITY OF ELEVATED SUPERCELLS NORTH OF THE WARM
   FRONT /MAINLY CAPABLE OF HAIL/...ALONG WITH AN INCREASING SURFACE
   BASED SEVERE THREAT NEAR/SOUTH OF THE WARM FRONT THIS MORNING ACROSS
   THE UPPER TX COAST/SOUTHERN LA. WITHIN AN INCREASINGLY MOIST AND
   HIGHLY SHEARED ENVIRONMENT...THIS INCLUDES THE POSSIBILITY OF AN
   EARLY DAY TORNADO/WIND DAMAGE THREAT THIS MORNING/EARLY AFTERNOON
   ACROSS SOUTHEAST TX INTO SOUTHERN LA.
   
   WITH TIME...THE AIRMASS WILL FURTHER DESTABILIZE INTO THIS AFTERNOON
   ESPECIALLY ACROSS CENTRAL/SOUTHERN LA AND SOUTHERN PORTIONS OF
   MS/AL...WITH 1000+ J/KG MLCAPE FOR AREAS WITHIN 150-200 MILES OF THE
   GULF COAST. LESSER...AND A BIT MORE UNCERTAIN...DESTABILIZATION IS
   EXPECTED CLOSER TO THE EAST-NORTHEASTWARD SURFACE LOW LATER
   TODAY/TONIGHT...LARGELY OWING TO PERSISTENT PRECIPITATION NEAR/NORTH
   OF THE WARM FRONT AND A LESSER INFLUX OF LOW-LEVEL MOISTURE.
   
   REGARDLESS...THIS DESTABILIZATION COUPLED WITH AN INCREASINGLY
   STRONG DEEP LAYER WIND FIELD...WITH 70-100 KT AT 500 MB AND
   110+ KT AT 250 MB...WILL RESULT IN DEEP LAYER SHEAR SUPPORTIVE OF
   ROTATING UPDRAFTS/SUPERCELLS. ACCENTUATED BY THE DEEPENING PHASE OF
   THE CYCLONE...EVENTUAL QLCS DEVELOPMENT SEEMS LIKELY TO OCCUR THIS
   AFTERNOON INTO TONIGHT NEAR/AHEAD OF THE EASTWARD-ADVANCING COLD
   FRONT...ALTHOUGH DISCRETE SUPERCELLS WILL REMAIN POSSIBLE WITHIN THE
   WARM SECTOR AND NEAR/IMMEDIATELY AHEAD OF THE EVOLVING QLCS...WHICH
   SEEMS LIKELY TO CROSS LA AND THE SOUTHERN HALVES OF MS/AL THROUGH
   TONIGHT. POTENTIALLY WIDESPREAD DAMAGING WINDS WILL BE POSSIBLE WITH
   SUSTAINED BOWING SEGMENTS. FURTHERMORE...A FEW STRONG/POTENTIALLY
   LONG-LIVED TORNADOES WILL ALSO BE POSSIBLE WITH DISCRETE SUPERCELLS
   AND/OR EVENTUAL EMBEDDED MESO-VORTICES LATER THIS
   AFTERNOON/TONIGHT...ESPECIALLY GIVEN 200-500 M2/S2 0-1 KM SRH
   COINCIDENT WITH A 50-70 KT LOW LEVEL JET LATE THIS
   AFTERNOON/TONIGHT.
   
   WHILE THE OVERALL SYSTEM STRENGTHENS...INSTABILITY WILL WANE LATE IN
   THE PERIOD. EVEN SO...A SEVERE THREAT MAY REACH AS FAR EAST AS PARTS
   OF AL...SOUTHEAST TN...AND WESTERN GA LATER TONIGHT...WITH SOME
   POTENTIAL FOR AREAS INCLUDING COASTAL SC BY THE EARLY MORNING HOURS
   OF WEDNESDAY.
   
   ..GUYER/SMITH.. 12/25/2012
   
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