SWOD48
SPC AC 231003
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0403 AM CST MON FEB 23 2009
VALID 261200Z - 031200Z
THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH A ZONAL
FLOW PATTERN IN PLACE. A VERY SUBTLE UPPER-LEVEL TROUGH IS FORECAST
TO MOVE EWD ACROSS THE MS VALLEY THURSDAY/DAY 4 AND ACROSS THE ERN
SEABOARD FRIDAY. IN RESPONSE TO THIS SYSTEM...A WELL-DEVELOPED
LOW-LEVEL JET IS FORECAST TO TRANSPORT MOISTURE NWD INTO THE OZARKS.
LARGE-SCALE ASCENT WITH THE UPPER-LEVEL TROUGH AND LIFT ASSOCIATED
WITH THE LOW-LEVEL JET SHOULD PROMOTE THUNDERSTORM DEVELOPMENT
ACROSS THE OZARKS AND POSSIBLY THE LOWER OH VALLEY DURING THE DAY ON
THURSDAY. THIS ACTIVITY SHOULD SHIFT EWD ACROSS THE OH VALLEY AND
MID-MS VALLEY THURSDAY NIGHT REACHING THE ERN SEABOARD AND GULF
COAST STATES ON FRIDAY. THE GREATEST POTENTIAL FOR ISOLATED SEVERE
STORMS APPEARS TO BE ON THURSDAY ACROSS THE OZARKS WHERE SFC
DEWPOINTS COULD BE IN THE 50S F. HOWEVER...DUE TO WEAK
INSTABILITY...THE THREAT DOES NOT WARRANT AN OUTLOOK AREA ATTM.
BEYOND FRIDAY/DAY 5...MODEL FORECASTS ARE IN GENERAL AGREEMENT
BRINGING AN UPPER-LEVEL TROUGH INTO THE CNTRL U.S. SATURDAY/DAY 6.
AHEAD OF THIS TROUGH...MOISTURE AND INSTABILITY SHOULD RETURN NWD
INTO THE GULF COAST STATES. THIS COMBINED WITH STRONG VERTICAL SHEAR
ASSOCIATED WITH A BROAD MID-LEVEL JET MAY PROMOTE SEVERE
THUNDERSTORM DEVELOPMENT SATURDAY AFTERNOON. HOWEVER...THE TIMING
AND AMPLITUDE OF THE UPPER-LEVEL TROUGH REMAINS HIGHLY QUESTIONABLE.
PREDICTABILITY APPEARS TO LOW FOR AN OUTLOOK AREA ATTM.
..BROYLES.. 02/23/2009
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