SWODY3
SPC AC 280715
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0215 AM CDT WED MAY 28 2008
VALID 301200Z - 311200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY EWD
ACROSS THE MIDWEST/OH VALLEY...
...SYNOPSIS...
A FLAT RIDGE IS FORECAST ACROSS THE SRN THIRD OF THE CONUS THIS
PERIOD...WHILE MORE ACTIVE BELT OF WLYS PREVAILS ACROSS THE CENTRAL
AND NRN CONUS. A SERIES OF SMALL-SCALE VORTICITY MAXIMA --
COLLECTIVELY COMPRISING A SHORT-WAVE TROUGH -- ARE FORECAST TO MOVE
EWD ACROSS THE CENTRAL PLAINS AND INTO THE MIDWEST/GREAT LAKES
THROUGH THE PERIOD.
AT THE SURFACE...A RELATIVELY WEAK/NE TO SW-ORIENTED BAROCLINIC ZONE
ASSOCIATED WITH THE UPPER SHORT-WAVE TROUGH WILL ALSO MOVE EWD
ACROSS THE MIDWEST. THIS BOUNDARY SHOULD SERVE AS A FOCUS FOR STORM
DEVELOPMENT THROUGH THE PERIOD.
...MID MO VALLEY REGION EWD ACROSS THE MIDWEST/OH VALLEY...
CHALLENGING FORECAST IS APPARENT THIS PERIOD...AS COMBINATION OF
ONGOING STORMS AS THE PERIOD BEGINS AND DIFFICULTIES ASSOCIATED WITH
TIMING OF SMALL-SCALE FEATURES WITHIN BROAD ZONE OF FAST WLY FLOW
MAKE HIGHLIGHTING AREAS OF GREATEST THREAT DIFFICULT.
WIDESPREAD STORMS ARE FORECAST TO BE ONGOING AT THE START OF THE
PERIOD FROM THE MID MO VALLEY REGION ENEWD INTO THE UPPER GREAT
LAKES...IN A ZONE OF WARM ADVECTION ASSOCIATED WITH A STRONG SWLY
LOW-LEVEL JET. WITH TIME...IT APPEARS THAT A WEAK SURFACE LOW INVOF
THE MID MO VALLEY EARLY WILL SHIFT ENEWD INTO THE UPPER GREAT LAKES
REGION THROUGH THE DAY...AND THEN ON EWD INTO SRN ONTARIO/THE LOWER
GREAT LAKES THROUGH THE END OF THE PERIOD. AS THIS LOW MOVES
ENEWD...A WEAK/TRAILING COLD FRONT SHOULD SAG SEWD ACROSS THE
MIDWEST/OH VALLEY.
WITH MOIST AIRMASS SPREADING NEWD ACROSS THE MIDWEST S OF THE
FRONT...DAYTIME HEATING AWAY FROM ONGOING CLOUDS/PRECIPITATION
COMBINED WITH THE EWD ADVECTION OF STEEP LAPSE RATES ALOFT WILL
RESULT IN MODERATE DESTABILIZATION. WITH THE FRONT -- AS WELL AS
CONVECTIVE BOUNDARIES -- LIKELY ACTING AS A FOCUS...EXPECT NEW STORM
DEVELOPMENT TO OCCUR BY EARLY AFTERNOON ACROSS A BROAD REGION
EXTENDING FROM IA/MO EWD TOWARD PA.
ALONG WITH AN AIRMASS SUPPORTIVE OF VIGOROUS STORMS...ROUGHLY
UNIDIRECTIONAL WLY/WSWLY FLOW ABOVE THE BOUNDARY LAYER -- INCREASING
WITH HEIGHT TO 60-65 KT AT H5 WILL SUPPORT ORGANIZED STORMS. WHILE
SHEAR WOULD SUPPORT UPDRAFT ROTATION...ATTM IT APPEARS THAT THE MAIN
STORM MODE SHOULD EVOLVE TOWARD SMALL-SCALE LINES/BOWS.
THUS...ALONG WITH HAIL...POTENTIAL FOR A FAIRLY WIDESPREAD DAMAGING
WIND EVENT APPEARS TO BE UNFOLDING. STORMS -- AND ASSOCIATED THREAT
FOR DAMAGING WINDS -- SHOULD SPREAD EWD ACROSS THE MID AND UPPER OH
VALLEY INTO PA AND VICINITY OVERNIGHT. ATTM...WILL INTRODUCE 30%
SEVERE PROBABILITY ACROSS PORTIONS OF THE AREA...BUT PROBABILITIES
WILL REQUIRE ADJUSTMENT IN LATER FORECASTS AS DEGREE AND LOCATION OF
GREATER THREAT BECOME MORE APPARENT.
..GOSS.. 05/28/2008
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