SWODY2
SPC AC 311727
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1227 PM CDT MON MAY 31 2010
VALID 011200Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS TUE/TUE NIGHT ACROSS PARTS OF
THE UPR MS AND MID MO VALLEYS INTO THE N CNTRL PLAINS...
...SYNOPSIS...
SOUTH OF A HIGHER LATITUDE LARGE-SCALE BLOCKING PATTERN...MODELS
INDICATE THAT A MODESTLY STRONG LOW AMPLITUDE WESTERLY FLOW WILL
PERSIST ACROSS THE NORTHERN AND CENTRAL TIER OF THE U.S. THROUGH
THIS FORECAST PERIOD. A SERIES OF PROGRESSIVE WEAK SHORT WAVE
IMPULSES EMBEDDED WITHIN THIS REGIME ARE EXPECTED TO CONTRIBUTE TO
CONVECTIVE POTENTIAL...AS THEY MIGRATE EAST OF THE ROCKIES THROUGH
THE UPPER MIDWEST AND NORTHEAST. ONE OF THESE FEATURES NOW APPEARS
TO BE IN THE PROCESS OF ADVANCING THROUGH THE NORTHERN GREAT
BASIN...WHILE ANOTHER CURRENTLY APPROACHES THE CENTRAL PACIFIC
COAST.
...MID MO/UPR MS VALLEYS INTO NORTH CENTRAL HIGH PLAINS...
FORCING ASSOCIATED WITH THE LEAD IMPULSE...COUPLED WITH ANOTHER
SIGNIFICANT IMPULSE PROGRESSING THROUGH THE SOUTHERN PERIPHERY OF A
BROADER SCALE EASTERN CANADIAN CYCLONIC CIRCULATION...MAY SUPPORT
STRENGTHENING UPWARD VERTICAL MOTION ACROSS CENTRAL/ EASTERN SOUTH
DAKOTA INTO SOUTHERN MINNESOTA AS EARLY AS TUESDAY MORNING. AS
LOW-LEVEL MOISTURE RETURN OCCURS TO THIS REGION...ON THE
NORTHEASTERN FRINGE OF WARMER...AND MORE STRONGLY CAPPING...
ELEVATED MIXED LAYER AIR...DESTABILIZATION SHOULD BECOME SUFFICIENT
FOR INCREASING CONVECTIVE DEVELOPMENT.
ACTIVITY IS EXPECTED TO CONSOLIDATE DURING THE DAY WITHIN A
LOWER/MID TROPOSPHERIC WARM ADVECTION REGIME NEAR/EAST OF THE MID
MISSOURI VALLEY...BEFORE EVENTUALLY INTENSIFYING AND BECOMING ROOTED
IN A SEASONABLY MOIST AND DESTABILIZING BOUNDARY LAYER ACROSS PARTS
OF SOUTHERN MINNESOTA AND IOWA...SOUTHWESTWARD INTO NEBRASKA. THIS
IS WHERE...WITH INSOLATION...IT APPEARS PROBABLE THAT MIXED LAYER
CAPE WILL REACH 1500-3000+ J/KG. BENEATH 30-50 KT WESTERLY 500 MB
FLOW...VERTICAL SHEAR WILL BE MODERATELY STRONG AND SUPPORTIVE OF
ONE OR MORE ORGANIZED STORM CLUSTERS CAPABLE OF PRODUCING STRONG
DAMAGING WINDS AND LARGE HAIL.
INITIAL STORM ACTIVITY ACROSS MINNESOTA/IOWA LIKELY WILL SPREAD WITH
DEEP LAYER MEAN WESTERLY FLOW ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY LATE TUESDAY AFTERNOON AND EVENING. AS THIS
OCCURS...STRONGEST NEW STORM DEVELOPMENT IS EXPECTED TO TREND
SOUTHWESTWARD TOWARD THE NOSE OF A 30-50 KT SOUTHERLY 850 MB JET
FORMING OVER THE CENTRAL PLAINS BY EARLY EVENING. THIS ACTIVITY MAY
REMAIN STRONG/SEVERE THROUGH MUCH OF THE NIGHT...WITH THE POTENTIAL
FOR DAMAGING WINDS AND VERY LARGE HAIL...AS IT SPREADS FROM THE
SOUTHERN/EASTERN NEBRASKA AND SOUTHWESTERN IOWA VICINITY TOWARD
NORTHERN ILLINOIS.
...NRN MID ATLANTIC STATES/LWR HUDSON VLY INTO SRN NEW ENGLAND...
DESTABILIZATION IS THE PRIMARY CONCERN WITH REGARD TO SEVERE STORM
POTENTIAL ALONG AND AHEAD OF A SOUTHEASTWARD ADVANCING COLD FRONT
TUESDAY. A MODESTLY SHEARED...30-40 KT+ WESTERLY DEEP LAYER MEAN
FLOW WILL PROVIDE POTENTIAL FOR ORGANIZED STORM DEVELOPMENT CAPABLE
OF PRODUCING POTENTIALLY DAMAGING WIND GUSTS. IF IT BECOMES MORE
CERTAIN THAT SURFACE HEATING WILL YIELD STEEP LOW-LEVEL LAPSE
RATES...SEVERE PROBABILITIES COULD BE INCREASED ENOUGH FOR A
CATEGORICAL SLIGHT RISK IN LATER OUTLOOKS FOR THIS TIME PERIOD.
..KERR.. 05/31/2010
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