SWODY3
SPC AC 250729
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT FRI SEP 25 2009
VALID 271200Z - 281200Z
...SYNOPSIS...
MODELS INDICATE THAT AN UPPER IMPULSE AND ASSOCIATED LOW/MID-LEVEL
CYCLONE...NEAR THE CENTRAL CANADIAN/U.S. BORDER AREA BY 12Z SUNDAY
...WILL UNDERGO FURTHER INTENSIFICATION WHILE DEVELOPING
SOUTHEASTWARD ACROSS THE UPPER MISSISSIPPI VALLEY/GREAT LAKES REGION
AND OHIO VALLEY BY 12Z SUNDAY. AS THIS OCCURS...ANOTHER VIGOROUS
UPSTREAM TROUGH IS PROGGED TO DIG TOWARD THE PACIFIC NORTHWEST
COAST...WHILE THE REMNANTS OF THE CLOSED LOW NOW OVER THE PLAINS
RAPIDLY LIFT ACROSS AND EAST OF MIDDLE AND NORTHERN ATLANTIC COASTAL
AREAS.
IN THE WAKE OF THE LEAD SYSTEM...A RIBBON OF HIGH MOISTURE CONTENT
AIR WILL BE SUPPRESSED SOUTH AND EAST OF ALL BUT THE FLORIDA
PENINSULA...PERHAPS PARTS OF DEEP SOUTH TEXAS...WHERE AT LEAST
SCATTERED THUNDERSTORM ACTIVITY REMAINS PROBABLE DURING THIS
FORECAST PERIOD. THUNDERSTORM PROBABILITIES WILL REMAIN OR BECOME
INCREASINGLY NEGLIGIBLE ELSEWHERE ACROSS THE U.S...WITH THE GREAT
LAKES REGION THE PRIMARY EXCEPTION.
...GREAT LAKES STATES...
LOW-LEVEL MOISTURE IS EXPECTED TO BE MARGINAL FOR VIGOROUS
CONVECTIVE DEVELOPMENT...AND THE MID-LEVEL COLD CORE MAY LAG THE
PRE-FRONTAL ENVIRONMENT...BUT GUIDANCE INDICATES THAT SUFFICIENT
DESTABILIZATION WILL OCCUR IN THE PRESENCE OF STRONG DYNAMIC FORCING
FOR LOW-TOPPED CONVECTIVE DEVELOPMENT ALONG/AHEAD OF THE STRONG COLD
FRONT. WHILE THE CONVECTION PROBABLY WILL NOT BE PARTICULARLY
VIGOROUS...IT SHOULD BE ENOUGH TO CONTRIBUTE TO THE DOWNWARD
TRANSFER OF MOMENTUM ASSOCIATED WITH THE STRENGTHENING AMBIENT
LOW-LEVEL WIND FIELDS...ESPECIALLY AS THEY INCREASE TO AROUND 50 KTS
NEAR/BELOW 850 MB ACROSS PARTS OF WISCONSIN AND THE UPPER PENINSULA
OF MICHIGAN SUNDAY AFTERNOON. THE RISK FOR STRONG...POTENTIALLY
DAMAGING...WIND GUSTS MAY PERSIST WITH CONVECTION THROUGH THE
EVENING HOURS AS IT OVERSPREADS LOWER MICHIGAN.
..KERR.. 09/25/2009
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