DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 240547
SWODY1
SPC AC 240546

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT FRI AUG 24 2012

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND EVENING
ACROSS PARTS OF CENTRAL AND EASTERN NORTH DAKOTA...

...SYNOPSIS...
WITHIN THE PRIMARY BELT OF WESTERLIES NEAR THE CANADIAN/U.S. BORDER
AREA...A VIGOROUS SHORT WAVE IMPULSE...NOW DIGGING TO THE SOUTHEAST
OF THE CANADIAN ROCKIES...IS FORECAST TO ACCELERATE EASTWARD THROUGH
THE CANADIAN PRAIRIES AND NORTHERN U.S. PLAINS BY 12Z SATURDAY...AS
ANOTHER STRONG UPSTREAM IMPULSE DIGS ACROSS THE NORTHEAST PACIFIC.
FAIRLY DEEP SURFACE CYCLOGENESIS MAY ACCOMPANY THIS
DEVELOPMENT...WITH THE PRIMARY LOW MIGRATING ACROSS SOUTHERN
SASKATCHEWAN INTO WEST CENTRAL MANITOBA. GUIDANCE IS ALSO
SUGGESTIVE THAT A SECONDARY WAVE FORMING SOUTH OF THE INTERNATIONAL
BORDER MAY MIGRATE ACROSS CENTRAL NORTH DAKOTA DURING THE LATE
AFTERNOON AND EVENING HOURS. HOWEVER...IN THE WAKE OF A WEAKER
PRECEDING SHORT WAVE IMPULSE...WHICH WILL LIKELY LIFT NORTHEAST OF
THE UPPER GREAT LAKES REGION EARLY IN THE PERIOD...MOISTURE RETURN
TO THE WARM SECTOR OF THE DEVELOPING SURFACE SYSTEM PROBABLY WILL BE
INHIBITED...AT LEAST INITIALLY.

HIGHER MOISTURE CONTENT AIR /CHARACTERIZED BY PRECIPITABLE WATER
AROUND 1.75 TO 2 INCHES/ IS GENERALLY IS EXPECTED TO REMAIN CONFINED
TO THE CENTRAL/SOUTHERN PLAINS...AS WELL AS MID/SOUTH ATLANTIC
COASTAL AREAS...BENEATH WEAK MID/HIGH LEVEL WESTERLIES EXTENDING
ACROSS MUCH OF THE CENTRAL AND SOUTHERN TIER STATES. LINGERING
TROUGHING WITHIN THIS REGIME ACROSS THE SOUTHEAST MAY BEGIN TO
SLOWLY DEVELOP NORTHEASTWARD THROUGH SOUTHERN MID ATLANTIC COASTAL
AREAS...AROUND THE WESTERN PERIPHERY OF THE ATLANTIC SUBTROPICAL
RIDGE. AT THE SAME TIME...IT APPEARS THAT A REMNANT UPSTREAM
CYCLONIC CIRCULATION WILL GRADUALLY SHIFT EAST OF THE FOUR CORNERS
REGION INTO THE SOUTH CENTRAL HIGH PLAINS.

...NORTHERN PLAINS...
IT IS POSSIBLE THAT EARLY DAY CONVECTIVE CLOUD COVER AND
PRECIPITATION ASSOCIATED WITH LOWER/MID TROPOSPHERIC WARM ADVECTION
MAY SLOW WARM SECTOR SURFACE HEATING...PARTICULARLY ACROSS NORTH
DAKOTA. COUPLED WITH SLOW BOUNDARY LAYER MOISTURE
RETURN...DESTABILIZATION WILL PROBABLY REMAIN A POINT OF UNCERTAINTY
THROUGH MUCH OF THE DAY. HOWEVER...MODELS ARE SUGGESTIVE OF AT
LEAST A WINDOW OF OPPORTUNITY FOR SUBSTANTIVE DESTABILIZATION...AS
THE SOUTHERN FRINGE OF STRONGER MID-LEVEL HEIGHT FALLS SPREADS
ACROSS NORTH DAKOTA DURING THE LATE AFTERNOON AND EVENING HOURS.
MID-LEVEL LAPSE RATES WILL BE STEEP ...AND STRONGER PRE-FRONTAL
SURFACE HEATING MAY CONTRIBUTE TO AT LEAST A NARROW CORRIDOR OF
STEEP LOW-LEVEL LAPSE RATES ACROSS WESTERN SOUTH DAKOTA INTO THE
VICINITY OF THE SECONDARY SURFACE LOW MIGRATING ACROSS CENTRAL NORTH
DAKOTA BY AROUND 00Z. COUPLED WITH STRENGTHENING VERTICAL SHEAR
SUPPORTIVE OF ORGANIZED CONVECTION...INCLUDING SUPERCELLS...A PERIOD
OF SEVERE STORM DEVELOPMENT APPEARS POSSIBLE THIS EVENING WITH THE
RISK FOR LARGE HAIL AND DAMAGING WIND GUSTS...PERHAPS AN ISOLATED
BRIEF TORNADO.

...CENTRAL/SOUTHERN HIGH PLAINS...
MID-LEVEL FLOW WILL REMAIN WEAK ACROSS THE REGION...BUT MODELS
SUGGEST THAT A CORRIDOR OF STRONGER SURFACE HEATING MAY RESULT IN A
WEAKLY TO MODERATELY UNSTABLE AND FAIRLY DEEPLY MIXED BOUNDARY LAYER
NEAR/EAST OF THE LEE SURFACE TROUGH. THIS THERMODYNAMIC
ENVIRONMENT...COINCIDING WITH A MODEST SOUTHERLY LOW-LEVEL JET /30+
KT AT 850 MB/...APPEARS SUPPORTIVE OF CONVECTIVE DEVELOPMENT WITH AT
LEAST LOW PROBABILITIES FOR SEVERE WIND GUSTS DURING THE LATE
AFTERNOON AND EARLY EVENING HOURS.

..KERR/ROGERS.. 08/24/2012

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