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    Day 2 Outlook >
Aug 21, 2014 0600 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Thu Aug 21 05:33:29 UTC 2014 (Print Version | 20140821 1200Z Day 1 shapefile | 20140821 1200Z Day 1 KML)
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 Forecast Discussion
   SPC AC 210533

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1233 AM CDT THU AUG 21 2014

   VALID 211200Z - 221200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY TO THE
   OH VALLEY...

   ...SUMMARY...
   SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP FROM PORTIONS
   OF THE UPPER MISSISSIPPI VALLEY INTO THE OHIO VALLEY.  DAMAGING
   WINDS AND LARGE HAIL ARE THE PRIMARY THREATS WITH THIS ACTIVITY.

   ...UPPER MS VALLEY/OH VALLEY...

   EARLY MORNING WV IMAGERY DEPICTS A TRANSITORY SHORT-WAVE TROUGH
   EJECTING EWD ACROSS THE CNTRL DAKOTAS.  THIS FEATURE IS EXPECTED TO
   TOP THE RIDGE OVER THE UPPER MS VALLEY EARLY IN THE PERIOD BEFORE
   TURNING SEWD INTO THE UPPER GREAT LAKES REGION.  CONSIDERABLE AMOUNT
   OF CONVECTION IS NOTED AHEAD OF THIS FEATURE AT MIDNIGHT FROM SERN
   ND INTO NCNTRL SD.  THIS ACTIVITY SHOULD PROGRESS INTO SRN MN BY
   12Z.

   LATEST MODEL GUIDANCE SUPPORTS THE PROGRESSION OF SHORT WAVE INTO MN
   BY DAYBREAK AND SFC WARM FRONT DRAPED ACROSS MN/SRN WI IS EXPECTED
   TO MOVE LITTLE THROUGH THE PERIOD.  FOR THIS REASON EARLY MORNING
   THUNDERSTORMS WILL LIKELY NOT DISSIPATE PRIOR TO DIURNALLY-ENHANCED
   DESTABILIZATION.  MODEST NWLY FLOW...ON THE ORDER OF 30KT AT
   500MB...APPEARS ADEQUATE FOR UPWARD GROWTH OF TSTMS AS THEY TRACK
   ESEWD ALONG WARM FRONT.  FORECAST SOUNDINGS SUGGEST MODERATE
   BUOYANCY WILL DEVELOP ACROSS MUCH OF THE WARM SECTOR FROM SERN SD
   INTO THE OH VALLEY WHERE SBCAPE SHOULD EASILY EXCEED 3000 J/KG. 
   THERE IS SOME CONCERN THAT WARM FRONTAL CONVECTION COULD ORGANIZE
   INTO MORE EXPANSIVE THUNDERSTORM CLUSTERS THAT COULD SURGE SEWD INTO
   THE OH VALLEY DUE TO CONTRIBUTIONS OF FORWARD PROPAGATION.  AT THIS
   TIME WILL ONLY INTRODUCE 15 PERCENT SEVERE PROBS FOR WIND AND HAIL
   AS IT/S NOT REAL CLEAR HOW THIS CONVECTION WILL ULTIMATELY EVOLVE.

   FARTHER WEST ACROSS THE CNTRL PLAINS...POST SHORT WAVE AIRMASS IS
   FORECAST TO DESTABILIZE SIGNIFICANTLY FROM SERN SD INTO ERN NEB
   WHERE SBCAPE COULD APPROACH 4000 J/KG.  WV IMAGERY AND MODEL
   GUIDANCE DO NOT SUGGEST ANY MEANINGFUL DISTURBANCE INTO THIS REGION
   DURING THE AFTERNOON/EVENING HOURS.  FOR THIS REASON IT APPEARS WEAK
   LOW LEVEL CONVERGENCE AND DIURNAL HEATING WILL BE THE PRIMARY
   MECHANISMS FOR POTENTIAL ISOLATED THUNDERSTORM DEVELOPMENT.  WEAK
   WARM ADVECTION ATOP THE BOUNDARY LAYER MAY ALSO CONTRIBUTE TO
   ELEVATED CONVECTION AFTER DARK...MAINLY ACROSS IA.  LARGE HAIL/GUSTY
   WINDS ARE THE MAIN THREATS WITH THIS ACTIVITY.

   ...LOWER CO RIVER VALLEY...

   00Z NAM GUIDANCE SUGGESTS WEAK UPPER LOW OVER SRN CA WILL DRIFT EAST
   TOWARD THE LOWER CO RIVER VALLEY.  A BELT OF MODEST SWLY FLOW AT
   500MB IS FORECAST ACROSS NWRN MEXICO INTO EXTREME SRN AZ.  WHILE
   THERMODYNAMIC PROFILES ARE NOT PARTICULARLY UNSTABLE OVER THE HIGHER
   TERRAIN OF AZ A SMALL POCKET OF BUOYANCY MAY EVOLVE BENEATH THE
   UPPER LOW.  IF SUFFICIENT INSTABILITY DEVELOPS NEAR THE MEXICAN
   BORDER THEN A FEW STRONG THUNDERSTORMS MAY ULTIMATELY EVOLVE DURING
   THE LATE AFTERNOON/EARLY EVENING HOURS.

   ..DARROW/MOSIER.. 08/21/2014

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z

        
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Page last modified: August 21, 2014
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