SPC AC 300540

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1240 AM CDT FRI AUG 30 2013

   VALID 311200Z - 011200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SYNOPSIS...
   WITHIN A BELT OF WESTERLIES NEAR THE CANADIAN/U.S. BORDER...A SERIES
   OF SHORT WAVE IMPULSES APPEAR LIKELY TO REMAIN PROGRESSIVE INTO AND
   THROUGH THIS FORECAST PERIOD.  ONE IMPULSE /NOW DIGGING ACROSS THE
   UPPER GREAT LAKES REGION/ IS FORECAST TO TURN EAST OF THE LOWER
   GREAT LAKES REGION BY 12Z SATURDAY...BEFORE CONTINUING ACROSS
   NORTHERN ATLANTIC COASTAL AREAS BY 12Z SUNDAY.  AT THE SAME TIME...A
   MORE SUBSTANTIVE UPSTREAM IMPULSE /CURRENTLY MIGRATING INLAND ACROSS
   THE CANADIAN ROCKIES AND PACIFIC NORTHWEST/ IS EXPECTED TO DIG
   THROUGH THE CENTRAL CANADIAN/U.S. BORDER AREA. 
   HOWEVER...CONSIDERABLE VARIABILITY EXISTS AMONG THE MODELS
   CONCERNING THE EVOLUTION AND STRENGTH OF THESE FEATURES...AS THE
   UPSTREAM PATTERN BEGINS TO AMPLIFY...WITH A RIDGE AXIS BUILDING
   NORTH OF A SUBTROPICAL HIGH CENTER OVER THE FOUR CORNERS
   REGION...THROUGH THE NORTHERN ROCKIES...AHEAD OF A SIGNIFICANT
   CLOSED LOW AND UPPER TROUGH OFF THE PACIFIC COAST.

   IN ASSOCIATION WITH THE EVOLVING UPPER PATTERN...ANOTHER EASTWARD
   SURGE OF VERY WARM ELEVATED MIXED LAYER AIR IS EXPECTED ACROSS MUCH
   OF THE NORTHERN AND CENTRAL PLAINS INTO THE UPPER MISSISSIPPI
   VALLEY.  THIS MAY OCCUR ABOVE AT LEAST MODEST LINGERING LOW-LEVEL
   MOISTURE AHEAD OF A COLD FRONT ADVANCING INTO THE EASTERN DAKOTAS
   AND MINNESOTA...BUT SEASONABLY HIGH MOISTURE CONTENT AIR LIKELY WILL
   BE CONFINED TO AREAS ALONG AND SOUTH OF AN INITIAL FRONT WITH THE
   LEAD IMPULSE...ACROSS PARTS OF THE MIDDLE MISSISSIPPI VALLEY AND
   SOUTHERN/LOWER GREAT LAKES REGION BY 12Z SATURDAY.  WEST OF THE
   ROCKIES...MONSOONAL MOISTURE IS EXPECTED TO CONTINUE TO STREAM INTO
   SOUTHERN PLATEAU AND GREAT BASIN.

   ...NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY...
   STRONGER MID/UPPER FORCING FOR UPWARD VERTICAL MOTION MAY REMAIN
   GENERALLY NORTH OF THE INTERNATIONAL BORDER THROUGH THE PERIOD.  AND
   WITH BOUNDARY LAYER MOISTURE/INSTABILITY LIKELY TO BE SOMEWHAT
   MODEST IN THE WAKE OF THE LEAD FRONT...SEVERE POTENTIAL FOR SATURDAY
   REMAINS UNCLEAR.  IT DOES NOT APPEAR OUT OF THE QUESTION THAT
   LOWER/MID TROPOSPHERIC WARM ADVECTION NEAR/JUST AHEAD OF THE
   SOUTHERN PERIPHERY OF THE DIGGING SHORT WAVE TROUGH COULD PROVIDE
   SUPPORT FOR ORGANIZED CONVECTIVE DEVELOPMENT ACROSS PARTS OF THE
   EASTERN DAKOTAS INTO SOUTHERN MINNESOTA LATE SATURDAY AFTERNOON AND
   EVENING.  DEEP LAYER SHEAR SHOULD BE SUFFICIENTLY STRONG...AND
   MID-LEVEL LAPSE RATES WILL BE STEEP... BUT SEVERE PROBABILITIES
   STILL APPEAR TO REMAIN BELOW THE CATEGORICAL SLIGHT RISK THRESHOLD
   AT THE PRESENT TIME.

   ...OHIO VALLEY INTO NORTHEAST...
   PRE-FRONTAL LOW-LEVEL MOISTURE MAY CONTRIBUTE TO POCKETS OF AT LEAST
   MODERATELY LARGE CAPE SUPPORTIVE OF CONSIDERABLE THUNDERSTORM
   ACTIVITY SATURDAY.  HOWEVER...GIVEN RELATIVELY WEAK MID-LEVEL LAPSE
   RATES...GENERALLY SEASONABLY MODEST BOUNDARY LAYER
   HEATING/MIXING...AND WEAK DEEP LAYER FLOW/SHEAR...THE RISK FOR
   SEVERE WIND AND HAIL STILL APPEARS LOW.

   ..KERR.. 08/30/2013

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z