Apr 11, 2011 1630 UTC Day 1 Convective Outlook
Updated: Mon Apr 11 16:30:43 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...numerous severe thunderstorms expected over parts of the tn valley and mid south this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20110411 1630 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110411 1630 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20110411 1630 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20110411 1630 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 111609
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1109 AM CDT MON APR 11 2011
   
   VALID 111630Z - 121200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS TODAY INTO TONIGHT OVER S-CNTRL
   KY...MIDDLE TN INTO NRN PARTS OF MS/AL...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER GREAT LAKES AND
   WESTERN NEW ENGLAND INTO THE LOWER MS VALLEY AND CNTRL/ERN GULF
   COAST STATES...
   
   ...WIDESPREAD DAMAGING WIND EVENT POSSIBLE TODAY INTO TONIGHT...
   
   ...KY/TN INTO LOWER MS VALLEY AND CNTRL GULF COAST STATES...
   
   A FOCUSED CORRIDOR OF DCVA ASSOCIATED WITH VIGOROUS VORTICITY
   MAXIMUM OVER THE SRN PLAINS COMBINED WITH A COUPLED UPPER-LEVEL JET
   STRUCTURE WILL ENHANCE DEEP ASCENT ACROSS THE REGION TODAY. 
   DEEPENING SURFACE LOW ATTENDANT TO THE SRN PLAINS VORTICITY MAXIMUM
   /ANALYZED OVER CNTRL AR AS OF 15Z/ WILL DEVELOP NEWD TO VICINITY OF
   S-CNTRL KY OR NRN-MIDDLE TN BY LATE AFTERNOON...REACHING THE VA
   PIEDMONT BY 12/12Z.  TRAILING COLD FRONT WILL ADVANCE EWD/SEWD
   THROUGH THE LOWER MS VALLEY AND CNTRL GULF COAST STATES.
   
   12Z REGIONAL SOUNDINGS ACROSS WARM SECTOR SHOWED THE PRESENCE OF
   RATHER WARM MIDLEVEL TEMPERATURES ALONG ANTICYCLONIC SIDE OF
   MIDLEVEL JET CORE WHICH WERE RESULTING IN POOR LAPSE RATES. 
   HOWEVER...VISIBLE SATELLITE IMAGERY DOES SUGGEST THAT RELATIVELY
   STRONG DIABATIC HEATING WILL OCCUR TODAY ACROSS THE WARM SECTOR. 
   WHEN COUPLED WITH COOLING MIDLEVEL TEMPERATURES /IN ASSOCIATION WITH
   12-HR HEIGHT FALLS OF 100-150 M AT 500 MB/...AIR MASS IS EXPECTED TO
   BECOME WEAKLY TO MODERATELY UNSTABLE WITH MLCAPE VALUES RANGING FROM
   500-1000 J/KG OVER THE TN VALLEY TO 1000-1500 J/KG ALONG THE GULF
   COAST.
   
   LATEST CONVECTION-ALLOWING MODEL GUIDANCE IS IN RATHER GOOD
   AGREEMENT IN SUGGESTING THAT PRE-FRONTAL BAND OF TSTMS FROM S-CNTRL
   KY INTO THE ARKLAMISS WILL ORGANIZE THIS AFTERNOON AS THE INCREASING
   LARGE-SCALE FORCING FOR ASCENT BEGINS TO INTERACT WITH THE
   DESTABILIZING AIR MASS.  GIVEN THE STRENGTHENING DEEP-LAYER WIND
   FIELD AND TENDENCY FOR DEEPER BOUNDARY-LAYER MIXING WITHIN THE WARM
   SECTOR...SETUP APPEARS FAVORABLE FOR A POTENTIALLY WIDESPREAD
   DAMAGING WIND EVENT ACROSS PORTIONS OF THE TN AND LOWER MS VALLEYS
   INTO CNTRL GULF COAST STATES TODAY INTO TONIGHT.
   
   A FEW TORNADOES WILL BE POSSIBLE ALONG AND SE OF MIGRATORY SURFACE
   LOW TRACK WHERE AN ISALLOBARICALLY BACKED WIND FIELD WILL ENHANCE
   LOW-LEVEL SHEAR.  A MORE SUBSTANTIAL TORNADO THREAT APPEARS TO BE
   LIMITED BY THE ANTICIPATED LINEAR CONVECTIVE MODE AND THE
   ABOVE-MENTIONED TENDENCY FOR DEEPER BOUNDARY LAYER MIXING WHICH WILL
   INCREASE T-TD SPREADS.
   
   ...LOWER GREAT LAKES INTO MID ATLANTIC STATES AND PORTIONS OF NEW
   ENGLAND...
   
   HIGHER-LATITUDE VORTICITY MAXIMUM OVER SWRN ONTARIO WILL TRANSLATE
   ENEWD THROUGH CNTRL/SRN QUEBEC THIS PERIOD WITH REGION BEING GLANCED
   BY MORE SUBSTANTIAL HEIGHT FALLS THROUGH THE PEAK OF THE DIURNAL
   HEATING CYCLE.  LATE MORNING SURFACE OBSERVATIONS INDICATE THAT
   BREAKS IN THE CLOUDS HAVE SUPPORTED SURFACE TEMPERATURES WARMING
   THROUGH THE 70S AS FAR N AS THE LEE OF LAKES ERIE AND ONTARIO.  THIS
   DIABATIC HEATING COUPLED WITH SOME BOUNDARY LAYER MOISTENING WILL
   YIELD AFTERNOON MLCAPE VALUES INCREASING TO 500-1500 J/KG.
   
   LOW-LEVEL ASCENT ALONG SYNOPTIC COLD FRONT AND PRE-FRONTAL OUTFLOW
   BOUNDARIES IN CONJUNCTION WITH GLANCING INFLUENCE WITH
   ABOVE-MENTIONED MIDLEVEL IMPULSE ARE EXPECTED TO FOSTER AN INCREASE
   IN STORMS THIS AFTERNOON WITH UPSCALE GROWTH INTO MULTIPLE LINE
   SEGMENTS LIKELY.  GIVEN THE RELATIVELY STRONG WSWLY WIND FIELD
   ALREADY IN PLACE AND THE DEVELOPMENT OF A WELL-MIXED BOUNDARY
   LAYER...THE POTENTIAL FOR CORRIDORS OF WIND DAMAGE WILL EXIST INTO
   TONIGHT ALONG WITH A RISK FOR A FEW TORNADOES.
   
   ..MEAD/STOPPKOTTE.. 04/11/2011
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z