Sep 5, 2011 2000 UTC Day 1 Convective Outlook
Updated: Mon Sep 5 19:49:13 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the southeast us this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20110905 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110905 2000 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
20110905 2000 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
20110905 2000 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 051945
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0245 PM CDT MON SEP 05 2011
   
   VALID 052000Z - 061200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
   PARTS OF EASTERN ALABAMA THROUGH WESTERN AND NORTH CENTRAL
   GEORGIA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
   ACROSS A LARGE PORTION OF THE EASTERN GULF AND SOUTH ATLANTIC COAST
   STATES...
   
   ...20Z UPDATE...
   NO SUBSTANTIVE CHANGES HAVE BEEN MADE TO THE PRIOR OUTLOOK...EXCEPT
   TO ACCOUNT FOR THE CONTINUED PROGRESSION OF THE SURFACE LOW
   CENTER...WHICH HAS MIGRATED NORTH OF MOBILE BAY...AND APPEARS LIKELY
   TO TURN NORTH NORTHEASTWARD ACROSS EASTERN ALABAMA LATE THIS
   AFTERNOON AND EVENING.  PRESSURE FALLS CONTINUE NEAR THE LOW
   CENTER...WITH AT LEAST SOME FURTHER INCREASE IN LOW-LEVEL FLOW AND
   SHEAR TO ITS EAST POSSIBLE.  THIS PROBABLY WILL MAINTAIN THE RISK
   FOR TORNADOES INTO/THROUGH THE NIGHT ACROSS THE PIEDMONT OF
   GEORGIA...PERHAPS INTO THE CAROLINAS.
   
   WITH THE DEVELOPMENT OF A DRY SLOT...ASSOCIATED WITH MID-LEVEL
   SUBSIDENCE NOSING AROUND THE EASTERN PERIPHERY OF THE CYCLONIC
   CIRCULATION...SEVERE POTENTIAL MAY BEGIN TO DIMINISH ACROSS MUCH OF
   EASTERN ALABAMA AS EARLY AS 00-03Z...AND MUCH OF WESTERN GEORGIA BY
   06Z.
   
   ..KERR.. 09/05/2011
   
   .PREV DISCUSSION... /ISSUED 1129 AM CDT MON SEP 05 2011/
   
   ...SERN STATES...
   
   VORTICITY MAXIMUM OVER SRN MS/ERN LA WILL LIFT NEWD THROUGH AL/GA
   TODAY IN ADVANCE OF UPSTREAM IMPULSE DIGGING SEWD INTO THE LOWER MS
   VALLEY.  WHILE THE FORMER WILL WEAKEN/DE-AMPLIFY OVER THE CNTRL
   APPALACHIANS TONIGHT...DEEP ASCENT WILL BE MAINTAINED ACROSS THE
   REGION BY AGEOSTROPHIC CIRCULATION ATTENDANT TO ENTRANCE REGION OF
   UPPER-LEVEL JET LIFTING NWD FROM THE CNTRL APPALACHIANS INTO LOWER
   GREAT LAKES.  AT THE SURFACE...MID MORNING MESOANALYSIS SHOWED LOW
   PRESSURE CENTERS N OF GPT AND OVER W-CNTRL AL WITH AN INTENSIFYING
   BAROCLINIC ZONE EXTENDING NEWD ALONG THE APPALACHIANS INTO WRN VA.
   THIS BOUNDARY IS EXPECTED TO REMAIN QUASI-STATIONARY THROUGH THE D1
   PERIOD WITH THE SURFACE LOWS CONSOLIDATING AND DEVELOPING SLOWLY
   NEWD ALONG IT...REACHING NWRN GA BY 06/12Z.  MEANWHILE...TRAILING
   COLD FRONT WILL CONTINUE SEWD THROUGH THE CNTRL GULF STATES.
   
   THE COMBINATION OF WARM-CORE...HYBRID SYSTEM AND WIDESPREAD CLOUDS
   WILL TEND TO LIMIT THE DEGREE OF AIR MASS DESTABILIZATION ACROSS THE
   WARM SECTOR TODAY WITH MLCAPE VALUES GENERALLY REMAINING AOB
   1000-1500 J/KG.  BUT...GIVEN THE MOIST...UNCAPPED ENVIRONMENT AND
   BROAD ASCENT ACROSS THE WARM SECTOR...EXPECT MULTIPLE BANDS OF TSTMS
   TO SPREAD NEWD THROUGH CNTRL/ERN AL AND WRN/CNTRL GA. 
   STRENGTHENING/BROADENING 40-50+ KT SLY FLOW IN THE 850-500 MB LAYER
   WILL RESULT IN MORE THAN SUFFICIENT VERTICAL SHEAR FOR SUPERCELLS
   AND LEWP STRUCTURES CAPABLE OF TORNADOES AND DAMAGING WINDS.  THOUGH
   INSTABILITY WILL DECREASE WITH TIME TONIGHT...MODEST LARGE-SCALE
   FORCING AND STRENGTHENING VERTICAL SHEAR WILL SPREAD NEWD INTO THE
   CAROLINA PIEDMONT...SUGGESTING A CONTINUED THREAT FOR A COUPLE
   TORNADOES AND DAMAGING WIND GUSTS.
   
   ...NEW ENGLAND AND MID ATLANTIC...
   
   UPLIFT ALONG COLD FRONT MAY FOSTER WIDELY SCATTERED TSTMS THIS
   AFTERNOON WITHIN A MODESTLY SHEARED ENVIRONMENT PRESENT IN ADVANCE
   OF NRN STREAM TROUGH MOVING INTO THE LOWER GREAT LAKES.  THOUGH THE
   BOUNDARY LAYER REMAINS QUITE MOIST...WIDESPREAD CLOUDS WILL LIMIT
   AIR MASS DESTABILIZATION AND THE POTENTIAL FOR A MORE ROBUST SEVERE
   WEATHER THREAT.  NONETHELESS...ISOLATED OCCURRENCES OF DAMAGING
   WINDS AND PERHAPS A BRIEF TORNADO WILL BE POSSIBLE WITH DIURNAL TSTM
   DEVELOPMENT.
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z