Apr 28, 2011 0100 UTC Day 1 Convective Outlook
Updated: Thu Apr 28 00:54:06 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the gulf states northward through the ohio valley and eastward into the appalachians through late evening....   Please read the latest public statement about this event.

Categorical Graphic
20110428 0100 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110428 0100 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
20110428 0100 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
20110428 0100 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 280050
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0750 PM CDT WED APR 27 2011
   
   VALID 280100Z - 281200Z
   
   ...THERE IS A HIGH RISK OF SVR TSTMS OVER ECNTRL/NERN AL...SERN TN
   AND NWRN GA...
   
   ...THERE IS A MDT RISK OF SVR TSTMS FROM ERN KY SWD INTO CNTRL AL...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE ERN U.S. ASIDE
   FROM NEW ENGLAND AND PENINSULAR FL...
   
   ...A HISTORICAL AND DANGEROUS OUTBREAK OF SEVERE THUNDERSTORM AND
   TORNADOES CONTINUES ACROSS PARTS OF THE TN VALLEY AND SRN STATES...
   
   CHANGES TO PREVIOUS OUTLOOK INCLUDE:
   
   1/ EXTEND HIGH RISK TO INCLUDE MORE OF NWRN GA
   2/ ADD HIGHER TORNADO PROBABILITIES IN MID-ATLANTIC
   3/ REDUCE MDT RISK SWD FROM THE OH VLY
   4/ TRIM WRN EDGE OF SVR RISKS IN TANDEM WITH FROPA
   
   1. SVRL TORNADIC SUPERCELLS CONTINUE ENE FROM ECNTRL MS AND CNTRL AL
   INTO ERN TN AT MID-EVENING.  FAVORED ZONE OF ADDITIONAL SUPERCELL
   DEVELOPMENT MAY OCCUR ALONG LOW-LEVEL CONFLUENCE ACROSS SWRN-CNTRL
   AL THROUGH LATE EVENING. THIS WILL BE AMID THE MOST VOLATILE
   COMBINATION OF EFFECTIVE SRH AND INSTABILITY AND THERE WILL BE A
   DANGEROUS STRONG-VIOLENT TORNADO RISK SPREADING ENE THROUGH
   CNTRL/NERN AL INTO NWRN AL AND SERN TN THROUGH THE EVENING HOURS. 
   AS A RESULT...THE HIGH RISK HAS BEEN EXPANDED EWD TO INCLUDE METRO
   ATLANTA. PLEASE REFER TO LATEST MESOSCALE DISCUSSIONS /SWOMCD/ AND
   WATCHES FOR UP-TO-THE-MINUTE METEOROLOGICAL DETAILS.
   
   2.  A LEAD MID-LEVEL WAVE CONTINUES TO MOVE NEWD INTO THE
   MID-ATLANTIC REGION.  INCREASING ASCENT...LOW-LEVEL CONFLUENCE ALONG
   THE FOOTHILLS...MLCAPE TO 1500 J PER KG AND 300+ 0-1KM SRH GAVE RISE
   TO SUPERCELLS WITH ISOLD TORNADOES EARLY THIS EVENING.  THERE WILL
   BE A RISK OF BRIEF TORNADOES THROUGH MID-EVENING...ESPECIALLY FROM
   CNTRL/NRN VA THROUGH DISTRICT OF COLUMBIA INTO CNTRL MD. 
   OTHERWISE...DMGG WIND GUSTS AND LARGE HAIL WILL BE LIKELY...BEFORE
   STORMS WEAKEN WITH LOSS OF INSOLATION.
   
   3.  ALTHOUGH THERE WILL STILL BE A THREAT FOR ISOLD TORNADOES...DMGG
   WINDS AND HAIL FROM THE OH RVR NWD TOWARD THE LOWER GREAT LAKES INTO
   LATE EVENING...HIGHEST PROBABILITIES OF SUSTAINED SVR WEATHER WILL
   REMAIN FROM KY COALFIELDS SWD.  CONSIDERABLE CLOUDS AND RAIN HAVE
   MITIGATED STRONG DESTABILIZATION TODAY PER 00Z ILN SOUNDING. 
   THEREFORE...MDT RISK/PROBABILITIES HAVE BEEN SHIFTED SWD.
   
   ..RACY.. 04/28/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z