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 281618
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1118 AM CDT SUN AUG 28 2011
   
   VALID 281630Z - 291200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF NEB AND IA
   INTO NRN KS AND NWRN MO...
   
   ...MID MO VALLEY INTO CNTRL PLAINS...
   
   SHORT-WAVE TROUGH AND ASSOCIATED 50-60 KT MIDLEVEL JET STREAK OVER
   THE NRN PLAINS WILL GLANCE THE REGION TODAY AS IT TRANSLATES
   SEWD...REACHING THE MID MS AND LOWER OH VALLEYS LATE TONIGHT INTO
   MON MORNING.  IN THE LOW LEVELS...SEVERAL AREAS OF LOW PRESSURE
   ANALYZED FROM CNTRL SD THROUGH WRN PARTS OF NEB/KS WILL CONSOLIDATE
   AS A THERMAL LOW OVER SWRN/S-CNTRL KS INTO NWRN OK BY
   AFTERNOON...WHILE A WEAK COLD FRONT PROGRESSES SWD THROUGH THE
   DAKOTAS AND NEB.
   
   ELEVATED TSTMS WHICH EARLIER PRODUCED DAMAGING WINDS AND HAIL ACROSS
   PARTS OF SERN SD HAVE SINCE WEAKENED WITH VISIBLE SATELLITE SHOWING
   WIDESPREAD HIGH CLOUDS SPREADING DOWNSHEAR ACROSS CNTRL/ERN NEB AND
   IA.  AS SUCH...IT APPEARS THAT THE STRONGEST AIR MASS
   DESTABILIZATION /I.E. MLCAPE VALUES APPROACHING 1500-3000 J PER KG/
   WILL OCCUR OVER WRN NEB INTO NRN KS...WHERE THE MORE INTENSE
   DIABATIC HEATING WILL ALIGN WITH A MOIST BOUNDARY LAYER AND STEEP
   MIDLEVEL LAPSE RATES.
   
   ONGOING STORMS OVER CNTRL NEB MAY INTENSIFY THIS AFTERNOON AS THEY
   MOVE/DEVELOP SEWD/SWD AND ENCOUNTER THE STRONGER INSTABILITY.  GIVEN
   THE VERTICALLY VEERING WIND PROFILES AND 35-45 KT OF DEEP NWLY SHEAR
   PER AREA PROFILER/VAD OBSERVATIONS...SETUP WILL FAVOR ORGANIZED
   STORM MODES INCLUDING SUPERCELLS AND BOWING STRUCTURES WITH A RISK
   FOR DAMAGING WINDS AND HAIL.  FARTHER E ACROSS ERN NEB...IA AND NWRN
   MO...ISOLATED OCCURRENCES OF DAMAGING WINDS AND HAIL WILL REMAIN
   POSSIBLE.  BUT...THE INCREASING CLOUDS AND DRIER BOUNDARY LAYER CAST
   GREATER UNCERTAINTY ON SEVERE STORM POTENTIAL.
   
   FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 2076.
   
   ...NEW ENGLAND...
   
   PER LATEST NHC GUIDANCE...T.S. IRENE WILL BEGIN TO ACCELERATE NNEWD
   ACROSS THE REGION IN RESPONSE TO AMPLIFICATION OF UPSTREAM
   SHORT-WAVE TROUGH OVER THE MID MS VALLEY/LOWER OH VALLEYS.  THOUGH A
   BRIEF TORNADO REMAINS POSSIBLE GIVEN THE STRONG LOW-LEVEL
   SHEAR...THE WIDESPREAD CLOUDS AND DISPLACEMENT OF INSTABILITY AXIS
   OFFSHORE PRECLUDE A MORE ROBUST THREAT.
   
   ...PACIFIC NW...
   
   MIDLEVEL VORTICITY MAXIMUM ALONG THE ORE COAST WILL PROGRESS EWD
   TOWARD THE ID BORDER DURING THE D1 PERIOD.  ABUNDANT SUNSHINE
   COUPLED WITH STEEP MIDLEVEL LAPSE RATES OBSERVED BY THE 12Z SLE
   SOUNDING  WILL CONTRIBUTE TO AFTERNOON MLCAPE VALUES APPROACHING
   500-1000 J/KG.  OROGRAPHIC INFLUENCES AND FORCING FOR ASCENT
   ATTENDANT TO MIDLEVEL SYSTEM ARE EXPECTED TO FOSTER SCATTERED TSTMS
   THIS AFTERNOON AND EVENING ALONG AND E OF THE CASCADES.  FORECAST
   SOUNDINGS INDICATE THE DEVELOPMENT OF A DEEPLY MIXED SUB-CLOUD LAYER
   WHICH WILL PROMOTE STRONG DOWNDRAFTS AND THE POTENTIAL FOR DAMAGING
   WINDS WITH THESE STORMS.
   
   ..MEAD/GRAMS.. 08/28/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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