Categorical Graphic
Probabilistic Tornado Graphic
Probabilistic Damaging Wind Graphic
Probabilistic Large Hail Graphic

   SPC AC 262000
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0300 PM CDT SAT JUN 26 2010
   
   VALID 262000Z - 271200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS SERN SD...FAR NERN
   NEB...SWRN MN AND NWRN IA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN/CENTRAL PLAINS
   TO UPPER MS VALLEY...
   
   ...NERN NEB...
   OBJECTIVE ANALYSES INDICATED THE AIR MASS ALONG THE MID MO VALLEY
   HAS BECOME VERY UNSTABLE...THUS FAR THIS AFTERNOON...WITH MLCAPE
   VALUES EXCEEDING 4000 J/KG.  GIVEN THAT STRONGER INSTABILITY EXTENDS
   SWD INTO NEB AND EFFECTIVE BULK SHEAR WILL INCREASE SWD ACROSS PARTS
   OF NERN NEB/NWRN IA INTO THE EVENING WITH APPROACH OF UPSTREAM
   TROUGH...MODERATE RISK/SEVERE PROBABILITIES HAVE BEEN EXPANDED SWD. 
   VERY LARGE HAIL AND EVENTUAL TORNADO DEVELOPMENT... SOME STRONG TO
   SIGNIFICANT...REMAIN LIKELY ACROSS THE MODERATE RISK AREA INTO THE
   EVENING.
   
   ...NRN HIGH PLAINS...
   AIR MASS OVER SERN MT/NERN WY HAS BECOME MODERATELY UNSTABLE IN
   ADVANCE OF A SHORTWAVE TROUGH...CURRENTLY EXTENDING FROM ALBERTA/
   WRN SASKATCHEWAN TO WRN WY PER WATER VAPOR IMAGERY.  FORCING FOR
   ASCENT ATTENDANT TO THIS TROUGH WILL SPREAD EWD AND SUPPORT
   ADDITIONAL TSTMS ACROSS ERN MT/NERN WY THIS AFTERNOON WITH ACTIVITY
   SHIFTING EWD INTO THE DAKOTAS.  GIVEN STRONG EFFECTIVE BULK SHEAR
   /40-50 KT/ AND MODERATE-STRONG INSTABILITY SUPERCELLS AND LINE
   SEGMENTS WILL BE POSSIBLE WITH THREATS FOR PRIMARILY HAIL AND STRONG
   WIND GUSTS.
   
   ...CENTRAL/ERN ND...
   TSTMS WILL CONTINUE TO DEVELOP AND SPREAD EWD ACROSS CENTRAL/ERN
   ND...POSING A SEVERE WEATHER THREAT GIVEN A MODERATELY UNSTABLE AIR
   MASS IN THIS REGION OF THE NRN PLAINS.  THIS INSTABILITY COMBINED
   WITH STRONG DEEP LAYER SHEAR /AROUND 50 KT/ SUGGESTS SUPERCELLS ARE
   POSSIBLE WITH FORECAST SOUNDINGS INDICATING HAIL... SOME VERY
   LARGE...MAY OCCUR ACROSS CENTRAL/ERN ND.  THUS... SIGNIFICANT HAIL
   PROBABILITIES HAVE BEEN EXTENDED NWD TO ACCOUNT FOR THIS THREAT. 
   SPC MESOSCALE DISCUSSION 1134 PROVIDES ADDITIONAL MESOSCALE DETAILS.
   
   ...CENTRAL/SRN MO...
   GIVEN REGIONAL RADAR TRENDS...LOW SEVERE WIND PROBABILITIES HAVE
   BEEN ADDED TO CENTRAL MO.
   
   ...SRN DELMARVA/ERN VA/ERN NC...
   MINOR ADJUSTMENTS TO THE LOW SEVERE WIND PROBABILITY AND GENERAL
   TSTM LINE WERE MADE ACROSS THIS AREA PER TRENDS IN REGIONAL RADAR
   IMAGERY.
   
   ..PETERS.. 06/26/2010
   
   .PREV DISCUSSION... /ISSUED 1130 AM CDT SAT JUN 26 2010/
   
   ...CENTRAL/NRN PLAINS...
   WV IMAGERY AND MORNING ANALYSIS SHOW BROAD UPPER TROUGH SHIFTING EWD
   FROM CENTRAL MT SWD INTO NRN UT...WHICH WAS ALSO AIDING IN THE
   EJECTION OF ANOTHER IMPULSE NEWD THROUGH NERN CO. THESE TWO SYSTEMS
   SHOULD BE PRIMARY CONTRIBUTORS FOR SEVERE THREAT THIS PERIOD. AT THE
   SURFACE...A BROAD AREA OF SURFACE LOW PRESSURE WAS SITUATED OVER WRN
   NEB/SD WITH A SURFACE TROUGH/FRONT EXTENDING SWD INTO WRN KS. AS
   UPPER TROUGH APPROACHES FROM THE WEST... SURFACE LOW SHOULD
   CONSOLIDATE AND DEEPEN SLIGHTLY AS IT SHIFTS EWD INTO SRN MN THIS
   EVE AND WI OVERNIGHT. SUBTLE WARM FRONT/OUTFLOW BOUNDARIES...WITH
   ONE EXTENDING FROM CENTRAL SD SEWD ALONG THE IA/NEB AND ANOTHER IN
   FAR SRN MN...ARE EXPECTED TO CONSOLIDATE AND SHARPEN BY LATE
   AFTERNOON IN SERN SD/SRN MN AS THE LOW MOVES EWD.
   
   AT MID MORNING...MOSTLY CLOUDY SKIES AND A FEW CLUSTERS OF ELEVATED
   STORMS WERE LOCATED ACROSS THE DAKOTAS...WITHIN WEAK WARM ADVECTION
   REGIME. ALTHOUGH MUCAPES AROUND 1500 J/KG AND CLOUD BEARING VERTICAL
   SHEAR MAY SUPPORT ISOLATED SEVERE HAIL INTO THE EARLY AFTERNOON
   HOURS...THE GREATER SEVERE THREAT LIKELY WILL WAIT UNTIL LATER TODAY
   AS STRONGER FORCING SPREADS IN FROM THE W AND SW AND GREATER
   BOUNDARY LAYER DESTABILIZATION OCCURS.
   
   THE MOST LIKELY AREA FOR INTENSE STORMS TO DEVELOP THIS AFTERNOON
   WILL BE SERN SD/NERN NEB/SWRN MN AND NWRN IA...AS UPPER WAVE
   APPROACHES FROM THE SW AND SURFACE BOUNDARY PROVIDES FOCUS FOR
   CONVECTIVE DEVELOPMENT. ALSO...THIS IS AN AREA WHERE SKIES HAVE BEEN
   SUNNY THROUGH THE MORNING AND MORE WARMING SHOULD RESULT IN EXTREME
   INSTABILITY BY MID AFTERNOON...WITH MLCAPES APPROACHING 4000 J/KG.
   ONCE SURFACE BASED STORMS DEVELOP...THE EXTREME INSTABILITY COMBINED
   WITH EFFECTIVE SHEAR NEAR 50 KT WILL BE VERY FAVORABLE FOR INTENSE
   SUPERCELLS. THOUGH THE GREATEST THREAT WILL BE VERY HAIL...BASEBALL
   SIZED AND BIGGER...STRONGLY CURVED HODOGRAPHS IN THE LOWER 1-2 KM
   INDICATES TORNADOES ARE ALSO LIKELY WITH DISCRETE
   SUPERCELLS...ESPECIALLY WITHIN MODERATE RISK AREA. OVERNIGHT...AS
   LOW LEVEL JET STRENGTHENS...CONVECTION MAY  CONSOLIDATE INTO A
   LINEAR MCS. LARGE HAIL AND WIND DAMAGE...AS WELL AS A TORNADO OR
   TWO...SHOULD PERSIST AS ACTIVITY SPREADS EWD ACROSS PORTIONS OF
   MN/WI/IA INTO EARLY SUNDAY.
   
   OTHER STORMS ARE ALSO LIKELY TO DEVELOP/SPREAD EWD ACROSS THE
   DAKOTAS SWD INTO NEB LATE TODAY AND TONIGHT...AND POSSIBLY NRN KS AS
   UPPER TROUGH APPROACHES FROM THE WEST. THOUGH THE COMBINATION OF
   CONVERGENCE/SHEAR AND INSTABILITY WILL NOT BE AS GREAT AS IN THE
   MODERATE RISK AREA...MODERATE TO STRONG INSTABILITY AND BAND OF
   40-50 KT MID LEVEL FLOW...WILL BE SUFFICIENT FOR SUPERCELLS WITH
   SEVERE HAIL AND WIND DAMAGE. GIVEN THE MORNING CLOUDS ACROSS NERN
   CO/WRN NEB AND EXPECTED SUBSIDENCE BEHIND DEPARTING UPPER
   IMPULSE...ONLY VERY ISOLATED HIGH BASED STORMS ARE EXPECTED ACROSS
   NERN CO...WRN KS AND FAR SERN WY LATE THIS AFTERNOON.
   
   ...IL/IN/OH...
   OUTFLOW FROM OVERNIGHT MCS COULD PROVIDE A FOCUS FOR STORM
   DEVELOPMENT LATER TODAY AS AIR MASS UNDERGOES DIURNAL
   DESTABILIZATION. THE MID LEVEL FLOW WILL NOT BE PARTICULARLY STRONG
   AND UPPER WAVE CURRENTLY MOVING THROUGH THE AREA MAY RESULT IN WEAK
   SUBSIDENCE FOR THE NEXT FEW HOURS. HOWEVER... CONVERGENCE MAY
   INCREASE BY EVENING AS LOW LEVEL JET SLOWLY STRENGTHENS TO 20 KT. IF
   STORMS DEVELOP...INSTABILITY WOULD BE FAVORABLE FOR ISOLATED WIND
   DAMAGE.
   
   ...SRN ATLANTIC COASTAL STATES WWD INTO OK...
   VERY MOIST...WARM AND HUMID AIR MASS SHOULD RESULT IN SCATTERED
   THUNDERSTORMS INTO THE EVENING HOURS. WHILE A FEW WET...SHORT LIVED
   MICROBURSTS APPEAR LIKELY...WEAK MID LEVEL FLOW/SHEAR AND POORLY
   DEFINED FOCUSING MECHANISMS MEANS THESE FEW EVENTS WOULD OCCUR
   WITHIN A LARGE AREA...SO ONLY LOW WIND PROBABILITIES ARE FORECAST.
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z