SWODY1
SPC AC 240520
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1220 AM CDT FRI OCT 24 2008
VALID 241200Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
AN INITIAL IMPULSE ASSOCIATED WITH THE STRONG POLAR JET STREAK
EMANATING FROM THE PACIFIC IS ALREADY BEGINNING TO DIG TO THE LEE OF
THE CANADIAN/NORTHERN U.S. ROCKIES. AND...MODELS INDICATE THAT A
MORE SIGNIFICANT SHORT WAVE IMPULSE WILL PROGRESS ACROSS THE
CANADIAN ROCKIES INTO THE CENTRAL CANADIAN PRAIRIES LATER TODAY/
TONIGHT. THIS IS PROGGED TO CONTRIBUTE TO A MORE RAPID
NORTHEASTWARD ACCELERATION OF THE MID/UPPER CLOSED LOW WHICH IS NOW
BEGINNING TO SLOWLY TURN EASTWARD INTO THE LOWER MISSOURI VALLEY.
ONE SIGNIFICANT IMPULSE PROGRESSING AROUND THE SOUTHERN/EASTERN
PERIPHERY OF THE CIRCULATION IS PROGGED TO LIFT NORTHEAST OF THE
OZARK PLATEAU...THROUGH THE LOWER OHIO/TENNESSEE VALLEYS EARLY IN
THE PERIOD...BEFORE CONTINUING NORTHWARD THROUGH THE LOWER GREAT
LAKES REGION AHEAD OF THE CIRCULATION TONIGHT. AS THIS STRONGER
FORCING FOR UPWARD VERTICAL MOTION REMAINS WELL TO THE NORTH OF A
LOW LEVEL BAROCLINIC ZONE ACROSS THE EASTERN GULF AND SOUTH ATLANTIC
COAST STATES...WAVE DEVELOPMENT ALONG THE BOUNDARY IS EXPECTED TO
REMAIN WEAK. COUPLED WITH NEGLIGIBLE BOUNDARY LAYER DESTABILIZATION
TO THE NORTH OF THE FLORIDA PENINSULA...DUE TO THE SLOW WEAKENING
AND RETREAT OF THE LARGE SURFACE RIDGE OFF THE ATLANTIC
COAST...CONVECTIVE POTENTIAL ACROSS THE SOUTHEAST IS EXPECTED TO BE
FAIRLY LIMITED THROUGH THIS FORECAST PERIOD.
...SOUTHEAST STATES...
AN INFLUX OF HIGH MOISTURE CONTENT AIR IS UNDERWAY...ALREADY
SUPPORTING WIDESPREAD PRECIPITATION IN AN ELEVATED WARM ADVECTION
REGIME...ABOVE THE NEAR SURFACE STABLE LAYER ASSOCIATED WITH THE
RETREATING SURFACE RIDGE. THIS ACTIVITY MAY LINGER ACROSS MUCH OF
NORTHERN FLORIDA THROUGH MUCH OF THE DAY...WHICH SHOULD LIMIT
APPRECIABLE BOUNDARY LAYER DESTABILIZATION TO THE PENINSULA... WHERE
SEA BREEZES COULD PROVIDE A FOCUS FOR SCATTERED LATE MORNING AND
AFTERNOON STORMS.
EVEN WITH SURFACE DEW POINTS AROUND 70F...MODEL FORECAST SOUNDINGS
INDICATE THAT WEAK MID-LEVEL LAPSE RATES AND NEARLY SATURATED
PROFILES WILL GENERALLY ONLY SUPPORT WEAK CONDITIONAL AND CONVECTIVE
INSTABILITY. HOWEVER...BENEATH MODERATE TO STRONG MID/HIGH LEVEL
FLOW NEAR THE SUBTROPICAL JET...30-50 KT SOUTHERLY 850
FLOW...ASSOCIATED WITH THE HEIGHT GRADIENT ON THE WESTERN EDGE OF
THE ATLANTIC RIDGE...WILL CONTRIBUTE TO SIZABLE LOW-LEVEL HODOGRAPHS
AS FAR SOUTH AS THE CENTRAL PENINSULA. THIS WILL PROVIDE AT LEAST A
LOW RISK FOR A SUPERCELL OR TWO...WITH POTENTIAL FOR THE DEVELOPMENT
OF STRONG LOW-LEVEL MESOCYCLONES CAPABLE OF PRODUCING A
TORNADO/LOCALIZED DAMAGING WIND GUSTS.
LARGE SCALE FORCING BENEATH BROADLY DIFLUENT UPPER FLOW IS EXPECTED
TO BE WEAK...BUT MOST FAVORABLE ALONG THE WEST COAST SEA BREEZE
DURING THE 16-20Z TIME FRAME...PERHAPS A BIT LATER ALONG THE EAST
COAST SEA BREEZE.
...MID MISSISSIPPI VALLEY INTO THE GREAT LAKES...
DESTABILIZATION NEAR/JUST AHEAD OF THE MID-LEVEL COLD CORE OF THE
UPPER LOW MAY BECOME SUFFICIENT FOR SCATTERED WEAK LOW TOPPED
THUNDERSTORMS...MAINLY THIS AFTERNOON...ACROSS CENTRAL/NORTHERN
ILLINOIS.
..KERR/BOTHWELL.. 10/24/2008
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