DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 020939
SWOD48
SPC AC 020938

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0338 AM CST FRI JAN 02 2009

VALID 051200Z - 101200Z

...DISCUSSION...

LATEST MEDIUM-RANGE IS RELATIVELY CONSISTENT IN THE EVOLUTION OF THE
LARGE-SCALE PATTERN /NAMELY IN THE MID AND UPPER-TROPOSPHERE/
THROUGH THE EXTENDED PERIOD. THE PRIMARY FEATURE OF INTEREST
CONTINUES TO BE LOW-LATITUDE TROUGH WHICH WILL TRANSLATE EWD FROM
BAJA/GULF OF CA AND NWRN MEXICO AT THE BEGINNING OF D4 /MON JAN 5TH/
TO TX BY THE BEGINNING OF D5 /TUE JAN 6TH/. THIS FEATURE THEN
DE-AMPLIFIES AS IT RAPIDLY LIFTS NEWD INTO THE OH VALLEY DURING THE
DAY TUE IN RESPONSE TO THE EVOLUTION OF AN UPSTREAM...FULL-LATITUDE
TROUGH OVER THE CNTRL PART OF THE NATION. THIS TROUGH THEN
PROGRESSES EWD THROUGH THE MS VALLEY AND EVENTUALLY OFF THE E COAST
BY D8 /FRI JAN 9TH/.

AT THE SURFACE...CONSISTENT DIFFERENCES ARE MAINTAINED ON D5 AS THE
ECMWF /WHEN COMPARED TO THE GFS/ DEVELOPS A LARGER WARM SECTOR OVER
THE GULF COAST STATES INTO TN VALLEY IN ADVANCE OF THE LEAD SHORT
WAVE TROUGH. MOREOVER...THE ECMWF DEVELOPS A BETTER-DEFINED SURFACE
LOW NEWD FROM LA AT 06/12Z INTO THE UPPER OH VALLEY BY 07/00Z. THIS
MODEL HAS SHOWN MUCH MORE RUN-TO-RUN CONSISTENCY THAN THE GFS...THUS
IT/S SOLUTION WAS GENERALLY FOLLOWED. WHILE THERE IS SOME CONCERN
REGARDING THE DEGREE OF INSTABILITY WITHIN THE SYSTEM WARM
SECTOR...SURFACE DEWPOINTS AOA 60 F AND STRONG VERTICAL SHEAR WILL
BE QUITE FAVORABLE FOR AN ORGANIZED SEVERE STORM EPISODE OVER PARTS
OF THE LOWER MS AND TN VALLEYS INTO THE CNTRL GULF STATES TUE INTO
TUE NIGHT.

SOME SEVERE WEATHER MAY CONTINUE INTO D6 /WED JAN 7TH/ OVER THE SERN
STATES IN ADVANCE OF LARGE-SCALE TROUGH. HOWEVER...GIVEN
UNCERTAINTIES IN CONVECTIVE EVOLUTION ON D5...NO ADDITIONAL AREAS
WILL BE DELINEATED ATTM.

..MEAD.. 01/02/2009

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