SPC AC 301630

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1130 AM CDT FRI AUG 30 2013

   VALID 301630Z - 311200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE WRN DAKOTAS AND
   VICINITY...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN UPPER GREAT
   LAKES/UPPER MIDWEST AREA...

   ...SYNOPSIS...
   A LARGE MID- AND UPPER-LEVEL RIDGE WHICH HAS PREVAILED ACROSS A
   LARGE PORTION OF THE U.S. FOR SEVERAL DAYS WILL PERSIST...THOUGH
   SOME FLATTENING OF THE RIDGE ON ITS NRN PERIPHERY AND SOME EROSION
   ON ITS ERN FRINGE IS EXPECTED THIS PERIOD -- RESULTING IN A
   MODEST/SLOW SWWD SUPPRESSION OF THE FEATURE.  THE FLATTENING ON THE
   NRN PERIPHERY OF THE RIDGE IS OCCURRING AS A SERIES OF SHORT-WAVE
   TROUGHS EMBEDDED WITHIN AN ENHANCED BELT OF WLY FLOW PROGRESS
   REPETITIVELY EWD ACROSS THE NRN U.S. AND ADJACENT SRN CANADA. 
   MEANWHILE...AS THESE FEATURES CREST THE RIDGE AND DROP SEWD...SOME
   WWD EXPANSION OF A WEAK MEAN TROUGH OVER THE WRN ATLANTIC WILL AID
   IN THE AFOREMENTIONED EROSION ON THE ERN EDGE OF THE LARGE-SCALE
   RIDGE.  MORE IMPORTANTLY...THE REPETITIVE PASSAGE OF THESE
   SHORT-WAVE FEATURES IN AN ANTICYCLONIC ARC AROUND THE PERIPHERY OF
   THE RIDGE WILL CONTRIBUTE TO ONGOING CONVECTIVE/SEVERE POTENTIAL
   ACROSS N CENTRAL PORTIONS OF THE COUNTRY THROUGH THE PERIOD.

   ...WRN DAKOTAS VICINITY...
   A PAIR OF WEAK UPPER FEATURES CROSSING THE NRN INTERMOUNTAIN REGION
   ATTM -- THE STRONGEST OF WHICH NOW ENTERING NWRN MT -- WILL MAINTAIN
   WEAK LARGE-SCALE ASCENT ACROSS MT AND INTO THE NRN HIGH PLAINS AREA
   THIS AFTERNOON.  WHILE MODEST CAPE IS FORECAST ACROSS MT GIVEN
   LIMITED LOW-LEVEL MOISTURE...GREATER DESTABILIZATION IS PROGGED TO
   CONTINUE ACROSS THE HIGH PLAINS VICINITY AND INTO NEB...ALONG
   TRAILING PORTIONS OF A WEAK COLD FRONT WHICH HAS BACKED WWD INTO
   THIS AREA.  WITH WEAK SLY FLOW MAINTAINING LOW 60S
   DEWPOINTS...CONTINUED HEATING WILL YIELD 1000 TO 2000 J/KG
   MIXED-LAYER CAPE.  THOUGH ISOLATED STORMS ARE FORECAST TO DEVELOP
   ACROSS MT -- WHICH MAY POSE ISOLATED WIND POTENTIAL...MORE
   WIDESPREAD DEVELOPMENT IS EXPECTED WITHIN THE MORE FAVORABLE AIRMASS
   ACROSS THE HIGH PLAINS.  AS STORMS DEVELOP IN THIS AREA...35 TO 45
   KT MID-LEVEL WLYS WILL CONTRIBUTE TO SHEAR SUPPORTIVE OF ORGANIZED
   STORMS/ISOLATED SUPERCELLS.  THE STRONGEST CONVECTION WILL BE
   CAPABLE OF PRODUCING LARGE HAIL AND LOCALLY DAMAGING WINDS INTO THE
   EVENING HOURS -- SUPPORTING A CONTINUATION OF THE SLIGHT RISK
   FORECAST OVER THIS REGION.

   ...SRN UPPER GREAT LAKES/UPPER MIDWEST REGION...
   A WEAK COLD FRONT EXTENDING FROM THE UPPER GREAT LAKES REGION WSWWD
   INTO THE MID MO VALLEY WILL CONTINUE TO MOVE SLOWLY SEWD THIS
   PERIOD...AS UPPER DISTURBANCES CREST THE DOMINANT RIDGE.  WITH A
   MOIST/HEATING BOUNDARY LAYER ALONG AND AHEAD OF THE FRONT BECOMING
   INCREASINGLY FAVORABLE FOR CONVECTIVE DEVELOPMENT...EXPECT ONGOING
   STORMS ACROSS NRN LOWER MI TO INCREASE...EXPANDING SWWD ALONG THE
   FRONT ACROSS LOWER WI AND INTO IA BY AFTERNOON -- ALONG WITH AN
   ASSOCIATED INCREASE IN STORM INTENSITY WITH TIME.  

   THOUGH DEEP-LAYER FLOW WILL REMAIN SOMEWHAT MODEST -- WITH ONLY 25
   KT LOWER AND MID-TROPOSPHERIC WNWLYS ACROSS THE REGION...SHEAR WILL
   BE SUFFICIENT IN CONJUNCTION WITH ANTICIPATED MODERATE
   DESTABILIZATION TO SUPPORT SOME SEVERE RISK WITHIN STRONGER
   CELLS/CONVECTIVE CLUSTERS.  GIVEN EXPECTED DESTABILIZATION AND
   HI-RES CONVECTION-ALLOWING MODELS ALL SUPPORTING THE AFOREMENTIONED
   SCENARIO...UPGRADE TO 15% HAIL AND WIND PROBABILITY/SLIGHT RISK
   FORECAST APPEARS WARRANTED FOR THE EXPECTED AFTERNOON/EVENING
   MAXIMUM IN CONVECTIVE INTENSITY.

   ..GOSS.. 08/30/2013

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