SPC AC 051628

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1128 AM CDT MON AUG 05 2013

   VALID 051630Z - 061200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
   ACROSS PARTS OF THE NORTHERN AND CENTRAL PLAINS...

   ...SYNOPSIS...
   TO THE SOUTH OF A HIGHER LATITUDE BLOCKING UPPER RIDGE...MODELS
   INDICATE THAT A SIGNIFICANT CLOSED LOW WILL CONTINUE TO SHIFT SLOWLY
   WEST SOUTHWEST OF HUDSON BAY THROUGH THE REMAINDER OF THIS FORECAST
   PERIOD.  AS THIS OCCURS...A WEAK CYCLONIC CIRCULATION... NOW OVER
   SOUTHERN ALBERTA/BRITISH COLUMBIA...APPEARS LIKELY TO SLOWLY
   PROGRESS INTO THE CONFLUENT REGIME ACROSS THE NORTHERN ROCKIES INTO
   NORTHERN PLAINS...BECOMING INCREASING SHEARED/DEFORMED AS IT DOES. 
   HOWEVER...THE ONSET OF WEAK MID-LEVEL HEIGHT FALLS MAY NOT REACH
   PORTIONS OF EASTERN MONTANA UNTIL LATE AFTERNOON/EARLY EVENING...AND
   PORTIONS OF NORTHERN WYOMING AND THE DAKOTAS UNTIL LATER TONIGHT.

   OTHERWISE...LITTLE CHANGE TO UPPER HEIGHTS ARE PROGGED THROUGH THE
   PERIOD FROM THE INTERMOUNTAIN REGION THROUGH THE PLAINS AND
   MISSISSIPPI VALLEY...WHERE FLOW WILL REMAIN BROADLY ANTICYCLONIC. 
   IN THE WAKE OF SUBTLE MID-LEVEL HEIGHT FALLS  ...ASSOCIATED WITH A
   COUPLE OF WEAK IMPULSES NOW MIGRATING EAST SOUTHEASTWARD THROUGH THE
   MIDDLE MISSOURI AND UPPER MISSISSIPPI VALLEYS...MID-LEVEL HEIGHTS
   MAY REBOUND.  AND THERE MAY BE LITTLE ...IF ANY...CHANGE TO THE VERY
   WARM AND CAPPING ELEVATED MIXED LAYER NOW PRESENT ACROSS MUCH OF THE
   CENTRAL AND SOUTHERN PLAINS ...WHERE HIGHER MOISTURE CONTENT
   AIR...CHARACTERIZED BY LOWER 70S SURFACE DEW POINTS...LINGERS ALONG
   A RESIDUAL BAROCLINIC ZONE ROUGHLY ACROSS NORTHEAST COLORADO/WESTERN
   AND SOUTHERN KANSAS INTO THE OZARK PLATEAU/LOWER MISSISSIPPI VALLEY.
   BUT MID/UPPER FLOW REMAINS SEASONABLY STRONG...FROM THE WEST
   NORTHWEST...ACROSS THE NORTHERN ROCKIES AND MUCH OF THE NORTHERN
   HALF OF THE PLAINS/UPPER MISSISSIPPI VALLEY.

   ...NORTHERN AND CENTRAL PLAINS....
   UNTIL LARGE-SCALE ASCENT INCREASES ACROSS EASTERN MONTANA AND THE
   DAKOTAS THIS EVENING INTO THE OVERNIGHT HOURS...WITH THE APPROACH OF
   THE UPPER IMPULSE...FORCING FOR CONVECTIVE DEVELOPMENT REMAINS
   UNCLEAR.  HIGHEST CONFIDENCE FOR STORM DEVELOPMENT...WHICH COULD
   REMAIN FAIRLY WIDELY SCATTERED...APPEARS TO BE IN ASSOCIATION WITH
   FAVORABLE OROGRAPHIC FORCING ON THE EASTERN SLOPES OF THE NORTHERN
   ROCKIES...POSSIBLY THE BLACK HILLS...LATE THIS AFTERNOON...BEFORE
   PROPAGATING EAST SOUTHEASTWARD INTO THE PLAINS.  IF THIS
   OCCURS...THE ENVIRONMENT ACROSS THE NORTHERN HIGH PLAINS IS EXPECTED
   TO BE CONDUCIVE TO ORGANIZED STRONG/SEVERE STORM DEVELOPMENT...
   INCLUDING ISOLATED SUPERCELLS.

   IT ALSO APPEARS POSSIBLE THAT A WEAK IMPULSE EMERGING FROM THE
   CENTRAL ROCKIES...AROUND THE PERIPHERY OF THE SUBTROPICAL
   HIGH...COULD CONTRIBUTE TO STORM DEVELOPMENT IN THE PRESENCE OF
   STEEP LAPSE RATES AND LARGE CAPE ACROSS WESTERN/CENTRAL KANSAS LATE
   THIS AFTERNOON.  IF MID-LEVEL INHIBITION IS OVERCOME...THE
   ENVIRONMENT APPEARS CONDUCIVE TO THE RISK FOR SEVERE HAIL AND WIND
   GUSTS...WITH POTENTIAL FOR UPSCALE CONVECTIVE GROWTH ACROSS KANSAS
   THIS EVENING AIDED BY MODEST STRENGTHENING OF A SOUTHERLY LOW-LEVEL
   JET.

   OTHERWISE...INCREASING THUNDERSTORM ACTIVITY IS POSSIBLE LATE THIS
   EVENING ACROSS THE DAKOTAS WITH THE STRENGTHENING LARGE-SCALE
   FORCING FOR UPWARD VERTICAL MOTION.  HOWEVER...THIS MAY NOT OCCUR
   UNTIL WELL AFTER THE ONSET OF BOUNDARY LAYER STABILIZATION...AND THE
   EXTENT OF THE SEVERE POTENTIAL REMAINS UNCLEAR AT THE PRESENT TIME.

   ...MID MISSOURI INTO UPPER MISSISSIPPI VALLEYS...
   IT STILL DOES NOT APPEAR OUT OF THE QUESTION THAT DESTABILIZATION IN
   THE PRESENCE OF STRONG SHEAR COULD BECOME SUFFICIENT TO SUPPORT AT
   LEAST LOW PROBABILITIES FOR SEVERE STORMS TODAY.  HOWEVER...WHERE
   POCKETS OF GREATER DESTABILIZATION COULD OCCUR REMAIN UNCLEAR...AND
   COVERAGE OF STORM DEVELOPMENT MAY REMAIN SPARSE AS THE MOST
   SIGNIFICANT FORCING FOR UPWARD VERTICAL MOTION TENDS TO SPREAD
   EASTWARD INTO THE MORE STABLE ENVIRONMENT ACROSS THE GREAT
   LAKES/OHIO VALLEY.

   ...ARIZONA...
   DAYTIME HEATING COULD YIELD A HOT AND DEEPLY MIXED BOUNDARY LAYER
   ACROSS THE PHOENIX METRO AREA AND ADJACENT DESERTS.  AS AN UPPER
   IMPULSE...WITHIN THE MONSOONAL MOISTURE PLUME WRAPPING ACROSS THE
   SOUTHERN PLAINS SUBTROPICAL HIGH CENTER...MIGRATES NORTHWARD OUT OF
   MEXICO ACCOMPANIED BY INCREASING CONVECTIVE DEVELOPMENT THIS
   EVENING...THE LOW-LEVEL ENVIRONMENT MAY REMAIN CONDUCIVE TO
   DOWNBURSTS AND STRONG CONVECTIVE SURFACE GUSTS.

   ..KERR/BUNTING.. 08/05/2013

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