SWODY2
SPC AC 011724
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1224 PM CDT MON SEP 01 2008
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS TUE/TUE NIGHT ACROSS PARTS OF
THE LWR MISSISSIPPI VALLEY....
...SYNOPSIS...
A SIGNIFICANT UPPER TROUGH WITHIN THE MAIN BELT OF POLAR WESTERLIES
IS ALREADY IN THE PROCESS OF LIFTING OUT OF THE GREAT BASIN...AS THE
NEXT SHORT WAVE APPROACHES THE PACIFIC NORTHEAST COAST. MODELS
INDICATE THAT THE LEAD IMPULSE WILL CONTINUE NORTHEASTWARD THROUGH
WESTERN ONTARIO BY LATE TUESDAY NIGHT EARLY WEDNESDAY...AS THE
UPSTREAM SYSTEM PROGRESSES INLAND ACROSS THE NORTHERN INTERMOUNTAIN
REGION/ROCKIES. AS SHORT WAVE RIDGING BUILDS DOWNSTREAM...ACROSS
QUEBEC...A CUT-OFF LOW IS EXPECTED TO LINGER OFF THE NORTH ATLANTIC
COAST. HOWEVER...THE MID-LEVEL CIRCULATION CENTER MAY SHIFT
WESTWARD A BIT...AS AN EMBEDDED IMPULSE ROTATES AROUND ITS WESTERN
PERIPHERY.
IN RESPONSE TO THESE DEVELOPMENTS...THE MID/UPPER OHIO VALLEY HIGH
CENTER...WITHIN A RIDGE ENCOMPASSING MUCH OF THE EASTERN U.S...IS
PROGGED TO WEAKEN. AND...MUCH OF THE MODEL GUIDANCE INDICATES THAT
THE WEST NORTHWESTWARD ACCELERATION OF THE REMNANTS OF GUSTAV WILL
SLOW CONSIDERABLY OVER PARTS OF EAST/NORTHEAST TEXAS.
...SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY/CENTRAL GULF COAST...
WHILE THE SLOWING MOTION OF GUSTAV MAY ENHANCE HEAVY RAINFALL
POTENTIAL TUESDAY...THIS COULD BECOME A LIMITING FACTOR TO
CONTINUING SEVERE POTENTIAL. HOWEVER...DESPITE THE ANTICIPATED
WEAKENING FROM TROPICAL STORM TO DEPRESSION DURING THIS PERIOD...
LOW-LEVEL SHEAR WILL REMAIN SUFFICIENT TO SUPPORT THE CONTINUING
RISK FOR ISOLATED GENERALLY BRIEF TORNADOES. HIGHEST PROBABILITY
FOR THIS SHOULD BE IN THE EASTERN SEMI CIRCLE OF THE REMNANT
CIRCULATION...ACROSS PARTS OF NORTHEAST TEXAS/SOUTHERN ARKANSAS/
LOUISIANA AND WESTERN MISSISSIPPI...WHERE THE LOW-LEVEL SHEAR IS
PROGGED TO REMAIN MAXIMIZED...AND WHERE BOUNDARY LAYER
MOISTURE/INSTABILITY WILL BE GREATEST...PARTICULARLY DURING THE
DAYTIME HOURS.
...CENTRAL PLAINS INTO THE UPPER MISSISSIPPI VALLEY...
STRONGEST MID/UPPER FORCING FOR UPWARD VERTICAL MOTION IS PROGGED TO
LIFT NORTH OF THE INTERNATIONAL BORDER BY EARLY TUESDAY. AS THIS
OCCURS...MODELS INDICATE THAT SOUTHERLY LOW-LEVEL FLOW FIELDS WILL
WEAKEN AHEAD OF A COLD FRONT ACCOMPANYING THE UPPER TROUGH. COUPLED
WITH ONLY MODEST DESTABILIZATION...PRIMARILY DUE TO GENERALLY WEAK
MID-LEVEL LAPSE RATES ALONG AND AHEAD OF THE FRONT...THE SEVERE RISK
WITH ANY ASSOCIATED THUNDERSTORM DEVELOPMENT APPEARS LIMITED.
...SOUTHERN PLATEAU/ROCKIES...
DESPITE A STRENGTHENING/DRYING WESTERLY MID/UPPER FLOW ACROSS THE
REGION...TO THE SOUTH OF THE POLAR TROUGH...LINGERING LOWER/MID
TROPOSPHERIC MOISTURE IS EXPECTED TO BE SUFFICIENT FOR SCATTERED
TERRAIN AIDED AFTERNOON/EVENING THUNDERSTORM ACTIVITY.
...NORTHEAST STATES...
LARGE-SCALE FORCING/DESTABILIZATION ASSOCIATED WITH THE IMPULSE
ROTATING AROUND THE PERIPHERY OF OFFSHORE CLOSED LOW MAY BE
SUFFICIENT FOR SCATTERED THUNDERSTORM ACTIVITY. THE BEST CHANCE FOR
THIS APPEARS TO BE ACROSS THE MOUNTAINS OF NORTHERN/WESTERN NEW
ENGLAND...WITH A TENDENCY TO DEVELOP SOUTHWARD OFF THE HIGHER
TERRAIN DURING THE AFTERNOON HOURS.
..KERR.. 09/01/2008
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