Monday, February 11, 2008

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 110819
SWODY3
SPC AC 110817

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0217 AM CST MON FEB 11 2008

VALID 131200Z - 141200Z

..THERE IS A SLGT RISK OF SVR TSTMS WED ACROSS THE CNTRL/SRN
FLORIDA PENINSULA....

..SYNOPSIS...
THE SPREAD AMONG MODELS CONCERNING UPPER FLOW DEVELOPMENTS DURING
THIS FORECAST PERIOD REMAINS SIZABLE. HOWEVER...GUIDANCE GENERALLY
INDICATES THE PRESENCE OF AN AMPLIFIED UPPER TROUGH OVER THE UPPER
GREAT LAKES REGION AND MID/LOWER MISSISSIPPI VALLEY AT 12Z
WEDNESDAY. THEREAFTER...A SHORT WAVE IMPULSE...PIVOTING AROUND THE
EASTERN PERIPHERY OF AN ELONGATED COLD VORTEX TO THE SOUTH OF HUDSON
BAY...IS PROGGED TO CONTRIBUTE TO A RAPID NORTHEASTWARD ACCELERATION
OF THE NORTHERN PORTION OF THIS UPPER TROUGH DURING THE DAY
WEDNESDAY. BUT...THE MODELS DO SUGGEST THAT THE MAIN IMPULSE
COMPRISING MUCH OF THE SOUTHERN PORTION OF THE BROADER SCALE TROUGH
WILL REMAIN PROGRESSIVE...AS ANOTHER STRONG SHORT WAVE TROUGH
CONTINUES TO DIG INLAND OF PACIFIC NORTHWEST COASTAL AREAS. A
SIGNIFICANT PORTION OF THE LATTER FEATURE IS FORECAST TO SPLIT OFF
THE MAIN BELT OF POLAR WESTERLIES...GRADUALLY EVOLVING INTO A CLOSED
LOW AS IT PROGRESSES INTO THE FOUR CORNERS STATES TOWARD THE OF THE
PERIOD.

..MID/SOUTHERN ATLANTIC SEABOARD...
IT APPEARS PROBABLE THAT THE UPPER PATTERN WILL SUPPORT AT LEAST A
COUPLE OF SIGNIFICANT SURFACE WAVES ALONG A FRONTAL ZONE THAT WILL
BE QUICKER TO ADVANCE EAST OF NORTHERN/MID ATLANTIC COASTAL AREAS
THAN THE SOUTHERN. DRYING ASSOCIATED WITH A PRE-FRONTAL WIND SHIFT
COULD END CONVECTIVE POTENTIAL SHORTLY AFTER 12Z WEDNESDAY ACROSS
MUCH OF THE SOUTHEAST. BUT...UNTIL THE SURFACE FRONT OVERTAKES THIS
BOUNDARY LATER IN THE DAY...A WEAK TO MODERATELY UNSTABLE AND
STRONGLY SHEARED ENVIRONMENT WILL MAINTAIN POTENTIAL FOR SEVERE
STORMS ACROSS THE CENTRAL/SOUTHERN FLORIDA PENINSULA...PERHAPS
EXTREME EASTERN NORTH CAROLINA.

HIGHEST PROBABILITIES FOR SEVERE STORMS APPEAR TO EXIST ACROSS THE
SOUTHEASTERN PORTION OF THE PENINSULA...WHERE THE FRONTAL PASSAGE
WILL BE LATEST...POSSIBLY ALLOWING FOR A PRE-FRONTAL SQUALL LINE
DURING THE PEAK AFTERNOON HEATING. WITH THE SURFACE FLOW PROGGED TO
VEER TO SOUTH SOUTHWESTERLY AHEAD OF THE FRONT EARLY IN THE
PERIOD...THE RISK FOR DAMAGING WINDS AND HAIL SEEM TO BE THE PRIMARY
SEVERE THREATS IN A MORE UNIDIRECTIONAL SHEAR REGIME. BUT...MORE
DISCRETE STORMS...INCLUDING ISOLATED SUPERCELLS COULD FORM ALONG THE
SOUTHEAST COASTAL SEA BREEZE...MAINLY SOUTH OF PALM BEACH.

..REMAINDER OF THE U.S...
WITH THE UPPER PATTERN SUPPORTING A WEAK COLD INTRUSION INTO THE
WESTERN/CENTRAL GULF OF MEXICO...AND MUCH STRONGER COLD INTRUSIONS
INTO THE NORTHEAST...THE NORTH CENTRAL STATES...AND THE
INTERMOUNTAIN WEST...CONVECTIVE POTENTIAL APPEARS LOW WEDNESDAY/
WEDNESDAY NIGHT.

.KERR.. 02/11/2008

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