Sep 16, 2006 1300 UTC Day 1 Convective Outlook
Updated: Sat Sep 16 16:36:09 UTC 2006
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the northern plains this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20060916 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20060916 1300 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20060916 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20060916 1300 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 161228
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0728 AM CDT SAT SEP 16 2006
   
   VALID 161300Z - 171200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT OVER
   PORTIONS OF EASTERN SD...SOUTHWEST MN...EASTERN NEB...AND WESTERN
   IA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM NORTHERN OK NORTHWARD
   THROUGHOUT MUCH OF THE CENTRAL AND NORTHERN PLAINS...
   
   ...OUTBREAK OF SEVERE THUNDERSTORMS CAPABLE OF VERY LARGE
   HAIL...DAMAGING WINDS...AND TORNADOES IS FORECAST TODAY OVER
   PORTIONS OF THE NORTHERN PLAINS AND MIDWEST REGION...
   
   MORNING WATER VAPOR LOOP SHOWS BROAD UPPER TROUGH OVER THE WESTERN
   UNITED STATES. SEVERAL FAST-MOVING SHORTWAVE TROUGHS ARE EMBEDDED
   IN CYCLONIC FLOW PATTERN.  ONE SUCH TROUGH IS CURRENTLY OVER
   UT...AND IS FORECAST TO TRACK RAPIDLY EASTWARD INTO THE CENTRAL/
   NORTHERN PLAINS BY THIS AFTERNOON.  THE ASSOCIATED SURFACE LOW IS
   EXPECTED TO DEEPEN RAPIDLY THROUGH THE AFTERNOON/EVENING AS IT
   TRACKS FROM SD INTO NORTHWEST MN.  CURRENT INDICATIONS ARE THAT
   PRIMARY CONVECTIVE FOCUS FOR INITIATION WILL BE ALONG/AHEAD OF
   SURFACE LOW/DRYLINE FROM CENTRAL SD INTO EASTERN NEB.
   
   ...ND/SD EARLY AFTERNOON...
   INITIAL SEVERE THUNDERSTORM DEVELOPMENT IS EXPECTED BY LATE
   MORNING/EARLY AFTERNOON NEAR DEEP SURFACE LOW OVER CENTRAL SD/ND. 
   INSTABILITY WILL BE RATHER MARGINAL IN THIS REGION.  HOWEVER... VERY
   STRONG UVVS IN EXIT REGION OF APPROACHING UPPER JET MAX... COUPLED
   WITH FAVORABLE DEEP LAYER VERTICAL SHEAR PROFILES...WILL PROMOTE A
   RISK OF LARGE HAIL IN STRONGER STORMS.
   
   ...SD/MN/NEB/IA THIS AFTERNOON THROUGH TONIGHT...
   SATELLITE IMAGERY CONFIRMS THAT GENERALLY CLOUD-FREE SKIES WILL
   REMAIN IN PLACE OVER THIS AREA TODAY...LEADING TO TEMPERATURES WELL
   INTO THE 80S AND DEEP MIXING.  THIS WILL HELP TO TRANSPORT RICH LOW
   LEVEL MOISTURE NORTHWARD AND DESTABILIZE AIRMASS /MLCAPE VALUES OF
   1500-2500 J/KG/.  SUBSIDENCE BEHIND OVERNIGHT SYSTEM WILL TEND TO
   SUPPRESS DEEP CONVECTION UNTIL EARLY AFTERNOON.  THUNDERSTORMS ARE
   THEN LIKELY TO RAPIDLY DEVELOP FROM THE SURFACE LOW OVER SD INTO
   PARTS OF EASTERN NEB ALONG TRAILING DRYLINE.  FORECAST SOUNDINGS IN
   THIS REGION SHOW EXTREMELY STRONG LOW AND DEEP LAYER VERTICAL SHEAR
   PROFILES FAVORABLE FOR SUPERCELLS AND TORNADOES /6KM SHEAR OF 50-70
   KNOTS AND 3KM HELICITY OF 300-500 M2/S2/.  INITIAL STORMS WILL HAVE
   THE POTENTIAL FOR VERY LARGE HAIL AND STRONG TORNADOES.  ACTIVITY
   WILL LIKELY REMAIN SUPERCELLULAR AS IT TRACKS ACROSS WESTERN IA AND
   SOUTHWEST MN...BEFORE EVENTUALLY ORGANIZING INTO A SQUALL LINE AFTER
   DARK WITH AN ENHANCED THREAT OF DAMAGING WINDS.
   
   ...KS/MO/OK...
   TRAILING DRYLINE/PACIFIC FRONT WILL EXTEND FROM EASTERN NEB INTO
   NORTHWEST OK BY THIS AFTERNOON.  WARM TEMPERATURES ALOFT AND WEAKER
   LARGE SCALE FORCING WILL BE PRESENT IN THIS REGION...LIKELY
   RESULTING IN MORE ISOLATED CONVECTION THAN FARTHER NORTH. 
   HOWEVER...SCATTERED THUNDERSTORMS ARE LIKELY TO DEVELOP DURING THE
   EVENING AS ENTRANCE REGION OF UPPER JET BEGINS TO AFFECT REGION. 
   MULTICELL STORMS CAPABLE OF DAMAGING WINDS AND HAIL WILL BE THE MAIN
   THREATS BEFORE STORMS WEAKEN OVER MO.
   
   ..HART/TAYLOR.. 09/16/2006
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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