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 151953
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0253 PM CDT MON AUG 15 2011
   
   VALID 152000Z - 161200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FOR LATE THIS AFTERNOON INTO
   TONIGHT FOR ERN MT AND ND...
   
   ...MT/ND...
   LATEST VISIBLE SATELLITE SHOWS AN OUTFLOW BOUNDARY...FROM ELEVATED
   CONVECTION IN ERN MT...HAS MOVED INTO WRN ND. AS THE BOUNDARY MOVES
   EWD THIS AFTERNOON...DESPITE LIMITED FORCING...LOW LEVEL CONVERGENCE
   AND WEAKENING CAPPING INVERSION MAY RESULT IN ISOLATED STORMS TO
   DEVELOP ALONG BOUNDARY. AIR MASS IS ALREADY UNSTABLE ...MLCAPES
   AROUND 3000 J/KG...AND 30-40 KT SHEAR WOULD BE FAVORABLE FOR ANY
   STORMS THAT DEVELOP TO BECOME SEVERE. HOWEVER...IT STILL APPEARS THE
   GREATER POTENTIAL FOR SEVERE STORMS WILL BE TONIGHT WHEN STRONGER
   FORCING...ASSOCIATED WITH UPPER WAVE MOVING INTO THE NRN
   ROCKIES...AND COLD FRONT MOVE EWD THROUGH THE REGION.
   
   ...SRN PLAINS...
   STRONG HEATING...SURFACE TEMPERATURES AROUND 100F...COMBINED WITH A
   RELATIVELY MOIST LAYER BETWEEN 850-700 MB HAS RESULTED IN A DENSE
   AREA OF BUILDING CU...ESPECIALLY OVER NWRN TX/SWRN OK. WITH A LITTLE
   ADDITIONAL HEATING...A FEW THUNDERSTORMS ARE EXPECTED TO DEVELOP
   FROM THESE CU OVER PORTIONS OF WRN/CENTRAL OK AND NRN TX. WLY MID
   LEVELS WINDS AROUND 15-20 KT IN THE MID LEVELS MAY RESULT IN LOOSELY
   ORGANIZED STORMS...AS THEY SHIFT EWD INTO THE EARLY EVENING HOURS.
   GIVEN THE HOT TEMPERATURES AND STEEP LOW LEVEL LAPSE RATES...
   ISOLATED STRONG TO PERHAPS SEVERE WIND GUSTS WILL BE POSSIBLE NEAR
   THE HEAVIER STORM CORES.
   
   REST OF FORECAST ON TRACK.
   
   ..IMY.. 08/15/2011
   
   .PREV DISCUSSION... /ISSUED 1121 AM CDT MON AUG 15 2011/
   
   ...SYNOPSIS...
   THE CONUS FLOW REGIME WILL BEGIN A TREND TOWARD MORE ZONAL WITH
   TIME...AS THE MIDLEVEL TROUGH OVER THE MID ATLANTIC LOSES AMPLITUDE
   AND MOVES SLOWLY NEWD...AND AN UPSTREAM TROUGH OVER THE PAC NW
   PROGRESSES EWD TO MT THIS AFTERNOON AND THE DAKOTAS OVERNIGHT.  THE
   MT/NRN PLAINS TROUGH WILL BE ACCOMPANIED BY A SURFACE COLD
   FRONT...WHILE A SURFACE CYCLONE ASSOCIATED WITH THE MID ATLANTIC
   MIDLEVEL TROUGH MOVES NEWD FROM JUST OFF THE NJ COAST TO NEAR THE SE
   NEW ENGLAND COAST THIS EVENING.  THE BAROCLINIC ZONE TRAILING FROM
   THE MID ATLANTIC CYCLONE WILL DRIFT SWD INTO THE N CENTRAL GULF OF
   MEXICO...AND THEN EXTEND NWD ACROSS THE ERN PLAINS STATES. 
   WIDESPREAD RAINFALL AND SOME EMBEDDED THUNDERSTORMS WILL CONTINUE
   ACROSS THE NRN MID ATLANTIC AND NEW ENGLAND...THOUGH WEAK
   INSTABILITY WILL LIMIT ANY SEVERE STORM THREAT.  REMNANT MCV/S AND
   OUTFLOW BOUNDARIES COULD FOCUS ADDITIONAL THUNDERSTORM DEVELOPMENT
   THIS AFTERNOON/EVENING ACROSS THE ERN PLAINS STATES.  HOWEVER...THE
   PRIMARY SEVERE STORM THREAT WILL RESIDE ACROSS THE NRN PLAINS LATER
   THIS AFTERNOON INTO TONIGHT.
   
   ...ERN MT/ND AREA LATER THIS AFTERNOON INTO TONIGHT...
   A THUNDERSTORM CLUSTER PERSISTS THIS MORNING ACROSS NE SD IN A ZONE
   OF LOW-LEVEL WAA ALONG THE SYNOPTIC WARM FRONT...AND IN ADVANCE OF A
   WEAK MIDLEVEL TROUGH CRESTING THE RIDGE.  THIS CONVECTION IS
   EXPECTED TO WEAKEN AFTER MIDDAY IN RESPONSE TO RISING HEIGHTS AND
   WARMING TEMPERATURES ALOFT.  FARTHER W...A CORRIDOR OF MID 60S
   BOUNDARY LAYER DEWPOINTS AND STEEP MIDLEVEL LAPSE RATES WILL COMBINE
   WITH DAYTIME HEATING TO SUPPORT MLCAPE VALUES NEAR 2500 J/KG ACROSS
   ND.  HOWEVER...LINGERING CONVECTIVE INHIBITION ACROSS ND...AND
   WEAKER INSTABILITY/WIDESPREAD HIGH CLOUDS OVER ERN MT SUGGEST THAT
   PHASING OF ASCENT /ALONG THE COLD FRONT AND IN ADVANCE OF A LEAD
   SHORTWAVE TROUGH NOW OVER CENTRAL MT/ WITH THE UNSTABLE WARM SECTOR
   MAY NOT OCCUR UNTIL LATER THIS EVENING NEAR THE MT/ND BORDER. 
   THUS...THE TIMING OF SEVERE STORM DEVELOPMENT COULD BE DELAYED UNTIL
   AFTER 22-23Z.
   
   STORMS THAT FORM ALONG THE COLD FRONT WILL DO SO IN AN ENVIRONMENT
   OF MODERATE INSTABILITY AND SUFFICIENT DEEP-LAYER VERTICAL SHEAR FOR
   SUPERCELLS.  ANY OF THE MORE DISCRETE SUPERCELLS COULD PRODUCE
   ISOLATED VERY LARGE HAIL GIVEN THE STEEP MIDLEVEL LAPSE RATES. 
   CONVECTIVE MODE IS SOMEWHAT UNCERTAIN...WITH DEEP-LAYER FLOW/SHEAR
   LARGELY PARALLEL TO THE COLD FRONT SUGGESTING A MIX OF CLUSTERS/LINE
   SEGMENTS AS CONVECTION EXPANDS IN COVERAGE THIS EVENING INTO EARLY
   TONIGHT.  DAMAGING WINDS AND LARGE HAIL WILL CONTINUE TO BE A RISK
   OVERNIGHT ACROSS ND IN CONJUNCTION WITH A REMAINING RESERVOIR OF
   LOW-LEVEL MOISTURE/INSTABILITY.
   
   ...CENTRAL MT TO NRN UT THIS AFTERNOON/EVENING...
   A BAND OF HIGH-BASED CONVECTION WILL BE POSSIBLE THIS
   AFTERNOON/EVENING ALONG THE COLD FRONT FROM SW INTO CENTRAL MT. 
   LIMITED LOW-LEVEL MOISTURE AND SOME DISRUPTION OF SURFACE HEATING BY
   CLOUDS WILL LIMIT INSTABILITY...BUT SUBSTANTIAL VERTICAL SHEAR AND
   SUFFICIENTLY STEEP LOW-LEVEL LAPSE RATES WILL PROMOTE SOME RISK OF
   STRONG/DAMAGING GUSTS.  A SIMILAR ENVIRONMENT WILL EXTEND SWD TO NRN
   UT...WHERE ISOLATED STRONG GUSTS WILL ALSO BE POSSIBLE.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z