Categorical Graphic
Probabilistic Tornado 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
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
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 201623
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1123 AM CDT WED APR 20 2011
   
   VALID 201630Z - 211200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF TX EWD ACROSS THE
   GULF COAST STATES...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
   NORTHEAST...
   
   ...CNTRL/ERN TX EWD TO GA...
   
   12Z REGIONAL SOUNDINGS SHOWED THAT AN EML/STEEP MIDLEVEL LAPSE RATE
   ENVIRONMENT REMAINS IN PLACE ACROSS A MOIST WARM SECTOR
   CHARACTERIZED BY BOUNDARY LAYER DEWPOINTS IN THE UPPER 60S TO LOWER
   70S.  DAYTIME HEATING ALONG THE SRN FRINGE OF CONVECTIVE DEBRIS
   ASSOCIATED WITH NOCTURNAL TSTM ACTIVITY SHOULD ALLOW TEMPERATURES TO
   WARM INTO THE 80S AND 90S.  WHEN COUPLED WITH THE HIGH MOISTURE
   CONTENT AND STEEP LAPSE RATES...AIR MASS IS EXPECTED TO BECOME
   MODERATELY TO STRONGLY UNSTABLE THIS AFTERNOON WITH MLCAPE VALUES
   INCREASING TO 2000-4000 J/KG.
   
   MIDLEVEL HEIGHTS ARE FORECAST TO REBOUND SLIGHTLY TODAY WITH THE
   PASSAGE OF UPPER TROUGH AXIS TO THE NE.  AS SUCH...TROPOSPHERIC WIND
   FIELD AND LARGE-SCALE FOR ASCENT WILL CORRESPONDINGLY DIMINISH. 
   NONETHELESS...THE PRESENCE OF THE SYNOPTIC COLD FRONT AND
   PRE-FRONTAL OUTFLOW BOUNDARIES ASSOCIATED WITH DECAYED OR ONGOING
   STORMS WILL SERVE AS THE FOCUS FOR DIURNAL TSTM DEVELOPMENT.  GIVEN
   THE DEGREE OF INSTABILITY AND AROUND 30 KT OF DEEP WLY SHEAR...SETUP
   WILL FAVOR THE DEVELOPMENT OF ORGANIZED MULTICELL CLUSTERS CAPABLE
   OF DAMAGING WINDS AND HAIL.  THIS THREAT WILL LIKELY CONTINUE
   THROUGH THE EVENING BEFORE DIMINISHING LATER TONIGHT WITH THE LOSS
   OF DAYTIME HEATING.
   
   ...NORTHEAST/MID ATLANTIC...
   
   SHORTWAVE TROUGH AND ASSOCIATED CORRIDOR OF 12-HR HEIGHT FALLS
   EXCEEDING 100-150 M AT 500 MB WILL TRANSLATE FROM THE GREAT LAKES
   AND OH VALLEY NEWD THROUGH NEW ENGLAND AND THE ST. LAWRENCE VALLEY
   TODAY.  ASSOCIATED SURFACE LOW OVER SWRN ONTARIO AS OF 16Z WILL
   CONCURRENTLY DEVELOP NEWD INTO FAR SRN QUEBEC BY 21/00Z WITH
   TRAILING COLD FRONT MOVING INTO THE HUDSON AND DE RIVER VALLEYS BY
   THIS TIME.  WARM FRONT IS EXPECTED TO LIFT NWD THROUGH AT LEAST THE
   LOWER HUDSON VALLEY BY LATE AFTERNOON/EARLY EVENING.
   
   MORNING VISIBLE SATELLITE IMAGERY INDICATES BREAKS IN THE CLOUDS
   AHEAD OF THE COLD FRONT ACROSS NY/PA WHICH SHOULD ALLOW FOR STRONGER
   DIABATIC HEATING.  WHEN COUPLED WITH BOUNDARY LAYER DEWPOINTS IN THE
   50S...EXPECT AFTERNOON MLCAPE OF 500-1000 J/KG.  LATEST MESOSCALE
   AND CONVECTION-ALLOWING MODEL GUIDANCE SUGGEST THAT WEAK CONVERGENCE
   ALONG THE COLD FRONT MAY LIMIT STORM COVERAGE THIS AFTERNOON INTO
   EVENING.  GIVEN THE STRONG WLY WIND FIELD IN PLACE...ANY STORMS THAT
   CAN DEVELOP WILL BE CAPABLE OF DAMAGING WIND GUSTS AND PERHAPS A
   BRIEF TORNADO.
   
   ...OK...
   
   THE DEVELOPMENT OF A NOCTURNAL LLJ WILL SERVE TO ENHANCE LIFT AND
   MOISTURE FLUX TO THE N OF SURFACE FRONT OVERNIGHT WITHIN A STEEP
   MIDLEVEL LAPSE RATE ENVIRONMENT...SUPPORTING MUCAPE OF 1000-1500
   J/KG.  ANY TSTMS THAT CAN DEVELOP WITHIN STRENGTHENING
   WAA/ISENTROPIC ASCENT REGIME WILL BE CAPABLE OF HAIL...SOME OF WHICH
   MAY EXCEED SEVERE CRITERIA.
   
   ..MEAD/SMITH.. 04/20/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z