SWOD48
SPC AC 051000
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CST THU MAR 05 2009
VALID 081200Z - 131200Z
THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH A
PROGRESSIVE UPPER-LEVEL TROUGH OVER THE GREAT PLAINS. THIS FEATURE
MOVES EWD INTO THE GREAT LAKES REGION AS ANOTHER UPPER-LEVEL TROUGH
DEVELOPS IN THE WRN STATES SUNDAY. ON SUNDAY/DAY 4...THE MODELS
FORECAST A LARGE AREA OF CONVECTION FROM THE UPPER-LEVEL TROUGH IN
THE MID TO UPPER MS VALLEY SSWWD INTO THE SRN PLAINS AND OZARKS. TWO
AREAS LOOK TO HAVE POTENTIAL FOR SEVERE THUNDERSTORMS. THE FIRST
EXISTS NEAR THE UPPER-LEVEL TROUGH OVER THE LOWER OH VALLEY EARLY IN
THE DAY. IN SPITE OF STRONG VERTICAL SHEAR AND STRONG LARGE-SCALE
ASCENT...INSTABILITY IN THIS AREA SHOULD BE QUITE WEAK. THE SECOND
AREA OVER THE SRN PLAINS AND OZARKS WILL BE IN AN AREA OF WEAKENING
LOW-LEVEL FLOW. HOWEVER...FORECAST SOUNDINGS SHOW ENOUGH INSTABILITY
WITH MODERATE VERTICAL SHEAR AND 60+ SFC DEWPOINTS. THIS SHOULD BE
SUFFICIENT FOR A SEVERE THREAT ALONG THE FRONT FROM ERN TX NEWD INTO
CNTRL AR ON SUNDAY AFTERNOON.
BEYOND SUNDAY/DAY 4...THE MEDIUM RANGE MODELS ARE IN GENERAL
AGREEMENT...BRINGING AN UPPER-LEVEL TROUGH INTO THE INTERMOUNTAIN
WEST AND FOUR CORNERS REGION. SOUTHWEST FLOW IN PLACE ACROSS THE SRN
PLAINS SHOULD ENCOURAGE MOISTURE RETURN AND AN AXIS OF INSTABILITY
SHOULD BE IN PLACE BY MONDAY AFTERNOON/DAY 5 FROM CNTRL TX INTO OK
AND AR. THE GFS AND ECMWF ARE ALSO IN AGREEMENT DEVELOPING
THUNDERSTORMS ALONG THE WRN EDGE OF THE INSTABILITY AXIS MONDAY
AFTERNOON. THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH STRONG
VERTICAL SHEAR AND A WELL-FOCUSED LOW-LEVEL JET SUGGESTING A
SUBSTANTIAL SEVERE THREAT COULD EXIST OVER MUCH OF THE SRN PLAINS
MONDAY AND MONDAY NIGHT.
INSTABILITY SHOULD CONTINUE TO BE IN PLACE ACROSS A RELATIVELY LARGE
WARM SECTOR TUESDAY/DAY 5 AND WEDNESDAY/DAY 6. IN ADDITION...THE
MODELS DEVELOP A LARGE AREA OF CONVECTION TUESDAY NIGHT ALONG A COLD
FRONT. HOWEVER...THE TIMING AND LOCATION FROM THE GFS AND ECMWF ARE
OUT OF PHASE WITH THE GFS MUCH FURTHER EAST. FOR THIS REASON WILL
NOT OUTLOOK A SEVERE THREAT AREA BEYOND DAY 5.
..BROYLES.. 03/05/2009
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