SWOD48
SPC AC 180951
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0351 AM CST FRI DEC 18 2009
VALID 211200Z - 261200Z
THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH A
PROGRESSIVE UPPER-LEVEL RIDGE IN THE CNTRL STATES AND A DEVELOPING
UPPER-LEVEL TROUGH IN THE WEST. BOTH THE GFS AND ECMWF ARE IN
AGREEMENT MOVING THE SYSTEM QUICKLY EWD INTO THE SRN PLAINS BY
TUESDAY NIGHT/DAY 5 BUT THE GFS IS THE MORE AMPLIFIED SOLUTION.
AHEAD OF THE SYSTEM...THE MODELS DEVELOP A STRONG LOW-LEVEL JET
WHICH SHOULD BRING LOW-LEVEL MOISTURE NWD INTO THE LOWER MS VALLEY
ON WEDNESDAY/DAY 6. STRONG VERTICAL SHEAR PROFILES ASSOCIATED WITH
THE LOW-LEVEL JET AND IN THE EXIT REGION OF A POWERFUL MID-LEVEL JET
CURRENTLY FORECAST BY THE MODELS WOULD BE SUFFICIENT FOR SEVERE
STORMS. THE GREATEST POTENTIAL WOULD EXIST ACROSS LA...MS AND AR
WEDNESDAY AFTERNOON AND EVENING. DUE TO THE STRENGTH OF THE SYSTEM
AND POTENTIAL FOR A MORE WIDESPREAD EVENT...WILL ADD A DAY 6 SEVERE
THREAT AREA FOR WEDNESDAY AND WEDNESDAY NIGHT IN THE LOWER MS
VALLEY. THIS AREA WILL LIKELY BE ADJUSTED AS UNCERTAINTY DECREASES
CONCERNING THE TIMING AND AMPLIFICATION OF THE UPPER-LEVEL TROUGH.
AS THE SYSTEM CONTINUES EWD ON THURSDAY/DAY 7...A POTENTIAL FOR
SEVERE THUNDERSTORMS WILL ALSO BE POSSIBLE ACROSS PARTS OF THE ERN
GULF COAST STATES AND SRN ATLANTIC BUT THE THREAT THERE IS NOT
ANTICIPATED TO BE GREAT ENOUGH FOR A THREAT AREA.
..BROYLES.. 12/18/2009
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