May 1, 2007 1300 UTC Day 1 Convective Outlook
Updated: Tue May 1 12:34:08 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Categorical Graphic
20070501 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20070501 1300 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20070501 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20070501 1300 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 011229
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0729 AM CDT TUE MAY 01 2007
   
   VALID 011300Z - 021200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE SRN GREAT
   LAKES ACROSS THE UPPER OH RIVER VALLEY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF CENTRAL TX...
   
   ...SRN GREAT LAKES INTO PA...
   SURFACE LOW NEAR LSE EARLY THIS MORNING IS FORECAST TO DEVELOP EWD
   ACROSS FAR SRN MI ALONG SURFACE WARM FRONT EXPECTED TO LIFT NWD NEAR
   THE MI-IN/OH BORDER DURING THE AFTERNOON.  THIS WILL OCCUR IN
   RESPONSE TO FAST MOVING SHORTWAVE TROUGH WHICH WILL SHIFT EWD ACROSS
   THE NRN GREAT LAKES TODAY.  SRN PERIPHERY OF STRONG WNWLY FLOW ALOFT
   ACCOMPANYING THIS WAVE WILL EXTEND OVER THE WARM SECTOR FROM NERN
   IND INTO WRN PA WITH H5 WINDS FROM 40-50 KT.  THIS WILL OCCUR IN
   CONCURRENCE WITH STRENGTHENING WSWLY LLJ INTO ERN OH/WRN PA/SWRN NY
   BY LATE TODAY AS H85 WINDS INCREASE AOA 25 KT.  THUS...OVERALL SHEAR
   WILL BECOME QUITE STRONG BY THE MID TO LATE AFTERNOON.  THE STRONG
   SHEAR WILL PERSIST ACROSS MUCH OF PA AFTER DARK AS LLJ AND SURFACE
   WAVE MOVE QUICKLY ESEWD OFF THE MID ATLANTIC COAST BY THE END OF THE
   PERIOD.  PRIMARY CONCERN FOR SEVERE THUNDERSTORMS WILL THEREFORE
   CENTER AROUND QUALITY OF LOW LEVEL MOISTURE AND ITS SUBSEQUENT
   INFLUENCES ON INSTABILITY.  APPEARS 10+C H85 DEW POINTS WILL ADVECT
   STEADILY ENEWD AWAY FROM THE MID MS RIVER VALLEY AND EXTEND INTO THE
   SRN GREAT LAKES EARLY TODAY.  RESULTANT DOWNWARD MIXING WILL AID
   ENEWD ADVECTION OF SURFACE MOISTURE AND ALLOW SURFACE DEW POINTS TO
   INCREASE INTO MID/UPPER 50S BY THE EARLY AFTERNOON INTO WRN PA BY
   LATE THIS AFTERNOON.  GIVEN STEEP LAPSE RATES AND ABUNDANT SURFACE
   HEATING...MLCAPE FROM 1000-1500 J/KG SHOULD BE QUITE COMMON WITHIN
   WARM SECTOR OVER THIS AREA TODAY.
   
   DEEP ASCENT...COLOCATED WITH STRENGTHENING SURFACE CONVERGENCE...
   SHOULD SUPPORT SCATTERED TO NUMEROUS THUNDERSTORMS FROM PORTIONS OF
   CENTRAL/NRN IL ACROSS THE SRN GREAT LAKES REGION BY THE MID TO LATE
   AFTERNOON.  SHEAR WILL BE MORE THAN ADEQUATE FOR SUPERCELLS AND
   SMALL LINES/BOW ECHOES ACROSS THIS REGION.  DAMAGING WINDS AND LARGE
   HAIL SHOULD BE PRIMARY THREATS...THOUGH LOW LEVEL SHEAR WILL BE
   FAVORABLE FOR A FEW TORNADOES ESPECIALLY NEAR H85-H7 JETS INTO NERN
   OH/WRN PA.  ACTIVITY WILL LIKELY BECOME MOST CONCENTRATED NEAR THE
   LLJ AXIS INTO WRN/CENTRAL PA BY THIS EVENING...WITH STORMS BECOMING
   INCREASINGLY ELEVATED NORTH AND EAST OF WARM FRONT INTO NY AND THE
   MID ATLANTIC AFTER DARK.
   
   ...TX...
   SEVERE THUNDERSTORM THREAT WILL BE RATHER NONDESCRIPT OVER TX TODAY
   AS SLOW MOVING UPPER LOW BEGINS TO LOSE AMPLITUDE AS IT SHIFTS ENEWD
   ACROSS OK THROUGH THE PERIOD.  SURFACE FEATURES ACROSS CENTRAL TX
   HAVE BECOME MUDDLED BY SEVERAL ROUNDS OF CONVECTION OVER THE PAST
   FEW DAYS...INCLUDING ONGOING MCS EARLY THIS MORNING.  PRIMARY
   SURFACE WARM FRONT/REINFORCED OUTFLOW BOUNDARY EXTENDING ROUGHLY E-W
   ACROSS CENTRAL TX FROM NEAR UTS/CLL TO NORTH OF AUS TO BETWEEN SJT
   AND JCT MAY PERSIST FOR MUCH OF THE DAY.  THIS FEATURE WILL EXIST
   ALONG NRN EDGE OF RICH GULF MOISTURE ACROSS SOUTH TX.  THOUGH DEEP
   ASCENT WILL REMAIN MOSTLY ABSENT...CONVERGENCE AND LIKELY
   DEVELOPMENT OF MODERATE TO STRONG INSTABILITY NEAR SURFACE
   BOUNDARIES MAY SUPPORT REDEVELOPMENT OF STRONG TO SEVERE STORMS OVER
   CENTRAL TX TODAY.  WLY FLOW ALOFT WILL WEAKEN...THOUGH MID LEVEL
   WINDS SHOULD STILL REMAIN AROUND 30 KT...AND SUPPORT SUFFICIENT
   SHEAR FOR ORGANIZED LINES AND ISOLATED SUPERCELLS.
   
   ..EVANS/GRAMS.. 05/01/2007
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z