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 031611
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1111 AM CDT TUE MAY 03 2011
   
   VALID 031630Z - 041200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN PA SWD TO NRN VA AND
   ERN WV...
   
   PREVIOUS OUTLOOK STILL APPEARS ON TRACK FOR A SEVERE THUNDERSTORM
   THREAT THIS AFTERNOON AND EVENING AHEAD OF THE COLD FRONT AND
   ASSOCIATED SURFACE WAVE MOVING NEWD FROM WV INTO ERN PA.
   
   THERE IS A QUESTION AS TO WHETHER THE MODELS ARE OVERDOING THE LOW
   LEVEL MOISTURE FLUX AND RESULTANT INSTABILITY FOR THIS AFTERNOON. 
   HOWEVER DEWPOINTS ARE RISING QUICKLY ACROSS VA INTO MD AT
   16Z...LEADING TO SUFFICIENT CONFIDENCE TO MAINTAIN THE 13Z OUTLOOK
   SCENARIO. THE 18Z SPECIAL SOUNDING FROM IAD SHOULD AID IN EVALUATING
   THE AIR MASS DESTABILIZATION.
   
   ONLY CHANGES WERE TO REDUCE THE RISK FROM SRN VA INTO NC WHERE
   INSTABILITY AND SHEAR WILL BE MORE LIMITED.
   
   ...SYNOPSIS...
   OZARKS SHORTWAVE IMPULSE EXPECTED TO CONTINUE ENE INTO THE OH AND TN
   VLYS TODAY...PHASING WITH NRN STREAM DISTURBANCE NOW OVER WI.  THE
   RESULTING LARGER SCALE TROUGH SHOULD ASSUME A NEARLY NEUTRAL TILT BY
   THE END OF THE PERIOD...AND EXTEND FROM LK HURON TO THE SRN
   APPALACHIANS.
   
   AT LWR LVLS...SFC WAVE NOW OVER WV SHOULD REMAIN ELONGATED BUT
   SOMEWHAT DEEPEN AS IT MOVES NEWD.  THE MAIN CENTER SHOULD REACH ERN
   PA BY EVE...WHILE TRAILING COLD FRONT CONTINUES E TO THE ERN SLOPES
   OF THE CNTRL/SRN APPALACHIANS.  THE LOW SHOULD CONTINUE NE INTO
   CNTRL/NRN NEW ENGLAND TONIGHT/EARLY WED AS COLD FRONT MOVES OFF THE
   MID ATLANTIC CST.  DIFFUSE WARM FRONT NOW OVER NRN MD AND PA SHOULD
   REFORM NWD INTO ERN NY/CNTRL NEW ENG LATER TODAY...ALLOWING A NARROW
   CORRIDOR OF MODIFIED GULF AIR TO SPREAD NNE ACROSS THE SUSQUEHANNA
   AND DELAWARE RVR VLYS.
   
   ...CNTRL APPALACHIANS AND ADJACENT PIEDMONT...
   BROAD BAND OF POST-COLD FRONTAL SHOWERS/EMBEDDED TSTMS NOW EXTENDING
   FROM PARTS OF THE LWR MS AND TN VLYS NNE INTO OH LIKELY WILL PERSIST
   AND SHIFT EWD WITH THE FRONT THROUGH THE PERIOD.  WHILE AMPLE
   UNIDIRECTIONAL CLOUD LAYER FLOW WILL BE PRESENT FOR
   ORGANIZED/SUSTAINED STORMS...WEAK ELEVATED INSTABILITY SHOULD KEEP
   ACTIVITY FROM POSING A SVR WEATHER THREAT.
   
   MEANWHILE...CONTINUED EWD MOTION OF OZARKS UPR IMPULSE SHOULD FOSTER
   GRADUAL STRENGTHENING OF WV/PA SFC WAVE AND ASSOCIATED SSWLY LLJ
   ALONG THE ERN SLOPES OF THE APPALACHIANS.  WHILE SATELLITE AND SFC
   OBS SHOW A RELATIVELY DRY POCKET OF AIR CONTINUING TO RESIDE OVER
   ERN NC AND ADJACENT REGIONS...THE LLJ SHOULD ALLOW MORE SUBSTANTIAL
   MOISTURE /PW AOA 1.25 INCHES/ TO CONTINUE SPREADING NNE AHEAD OF SFC
   WAVE.  COUPLED WITH SFC HEATING...THIS SHOULD YIELD POCKETS OF
   MODERATE INSTABILITY WITH SBCAPE OF 1500 TO PERHAPS 2000 J/KG OVER
   PARTS OF VA...ERN WV...MD AND SRN/ERN PA.  RELATIVELY WEAK MID LVL
   LAPSE RATES SHOULD...HOWEVER...LIMIT OVERALL DEGREE OF INSTABILITY.
   
   CONVERGENCE INVOF THE SFC LOW SHOULD FOSTER TSTM DEVELOPMENT BY
   EARLY-MID AFTN OVER PARTS OF PA/MD AND VA/WV.  DEVELOPMENT MAY OCCUR
   A BIT LATER SWD ALONG COLD FRONT INTO THE WRN CAROLINAS AND GA.
   GRADUAL STRENGTHENING OF SWLY MID/UPR LVL FLOW WITH APPROACH OF UPR
   TROUGH EXPECTED TO SHOULD ENABLE A FEW SUSTAINED
   STORMS...SUPERCELLS...AND BROKEN LINE SEGMENTS. THESE MAY CONTAIN
   LOCALLY DMGG WINDS AND...ESPECIALLY ALONG/AHEAD OF SFC LOW TRACK IN
   ERN WV/CNTRL MD AND PA...POSSIBLE TORNADOES.
   
   DESPITE CONTINUED INCREASE IN MID/UPR LVL FLOW...THE OVERALL SVR
   WEATHER THREAT SHOULD DIMINISH BY LATE EVE AS LOW LVL INSTABILITY
   WANES.
   
   ...ERN AL INTO GA/WRN SC...
   MODERATE INSTABILITY WILL DEVELOP AHEAD OF COLD FRONT CROSSING THE
   SRN APPALACHIAN REGION THIS AFTN.  BUT RELATIVELY WEAK MID LVL LAPSE
   RATES AND MORE MODEST WIND FIELD COMPARED TO POINTS FARTHER N
   SUGGEST THAT MULTICELLS WILL BE THE PRIMARY STORM MODE.  WHILE
   STRONG WIND GUSTS AND MARGINALLY SVR HAIL MAY OCCUR...ANY SVR THREAT
   SHOULD REMAIN ISOLD AND/OR OF LIMITED DURATION.
   
   ..HALES/CORFIDI/GUYER.. 05/03/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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