Dec 22, 2011 0600 UTC Day 1 Convective Outlook
Updated: Thu Dec 22 05:59:08 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20111222 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20111222 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
20111222 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
20111222 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 220555
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1155 PM CST WED DEC 21 2011
   
   VALID 221200Z - 231200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF THE LOWER MS
   VALLEY AND DEEP SOUTH...
   
   ...SYNOPSIS...
   A SHORT WAVE TROUGH CENTERED ACROSS WRN TX INTO COAHUILA WILL TRACK
   E/NEWD ACROSS TX THIS MORNING BEFORE DAMPENING AS IT ACCELERATES
   NEWD TOWARDS THE LOWER OH VALLEY BY EARLY EVENING. AT THE
   SURFACE...A WEAK CYCLONE WILL TRACK NEWD ALONG A FRONTAL ZONE OFF
   THE TX COAST...ACROSS THE LOWER MS VALLEY INTO NRN AL...AND
   EVENTUALLY INTO THE MID-ATLANTIC THROUGH EARLY FRI. 
   
   ...LOWER MS VALLEY/DEEP SOUTH...
   A SWATH OF RAIN/EMBEDDED TSTMS WITHIN AN ENVIRONMENT OF WEAK
   ELEVATED BUOYANCY WILL BE ONGOING AT 12Z/THU ACROSS ERN TX INTO
   PARTS OF THE LOWER MS VALLEY. THIS EXPANSIVE PRECIPITATION SHIELD
   SHOULD RETARD THE NWD RETREAT OF THE FRONT...WITH THIS BOUNDARY
   EXPECTED TO BISECT LA/MS INTO NRN AL BY 18Z. STRENGTHENING LOW-LEVEL
   SWLYS COUPLED WITH STRONGLY FORCED ASCENT THROUGH MID-LEVEL
   DCVA/LOW-LEVEL WAA SHOULD PROMOTE ACTIVITY DEVELOPING E/NEWD ALONG
   THE FRONTAL ZONE. DESPITE MEAGER INSTABILITY...STRONG LOW/DEEP-LAYER
   SHEAR SHOULD RESULT IN ORGANIZED LINE SEGMENTS PROMOTING A RISK FOR
   DAMAGING WINDS AND PERHAPS A BRIEF TORNADO.
   
   FARTHER E/SE...A SEPARATE AREA OF MORE DISCRETE TSTMS SHOULD FORM
   WITHIN THE OPEN WARM SECTOR ACROSS THE CNTRL GULF COAST. THIS
   SCENARIO IS INFERRED BY OPERATIONAL GUIDANCE WITHIN AN AXIS OF
   LOW-LEVEL CONFLUENCE AND DEPICTED BY CONVECTION-ALLOWING WRF-NMM AND
   HRRR GUIDANCE. DESPITE POTENTIALLY LIMITED SURFACE HEATING...65-70 F
   SURFACE DEW POINTS SHOULD BE SUFFICIENT FOR MLCAPE TO INCREASE TO
   BETWEEN 400-800 J/KG. 0-1 KM SRH AROUND 150-250 M2/S2 WILL SUPPORT A
   FEW SUPERCELLS CAPABLE OF PRODUCING TORNADOES/DAMAGING
   WINDS...PEAKING IN THE LATE MORNING TO MID-AFTERNOON.
   
   LOW-LEVEL MOISTURE AND INSTABILITY WILL WANE WITH NEWD EXTENT
   TOWARDS THE SRN APPALACHIANS...WITH A DIMINISHING SEVERE THREAT
   EXPECTED AFTER DARK AS THE SHORT WAVE IMPULSE WEAKENS AND BECOMES
   INCREASINGLY DIVORCED FROM THE WARM SECTOR.
   
   ..GRAMS/ROGERS.. 12/22/2011
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z