DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 121729
SWODY2
SPC AC 121727

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1227 PM CDT THU MAR 12 2009

VALID 131200Z - 141200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MODELS REMAIN CONSISTENT WITH LARGE SCALE SPLIT FLOW PREVAILING INTO
FRIDAY ACROSS THE CONUS. A BROAD SRN STREAM UPPER TROUGH WILL
MIGRATE EWD OVER THE SRN ROCKIES/FAR NRN MEXICO...WITH THE LEAD
PORTION OF THIS TROUGH TO OVERSPREAD THE SRN PLAINS ON FRIDAY.
DAY 2 WILL BE SIMILAR TO DAY 1 WITH A TSTM POTENTIAL ACROSS
CENTRAL/ERN TX INTO LOWER MS VALLEY...AND FROM PARTS OF CENTRAL/ERN
AZ INTO WRN NM/SW CO. IN THE LOW LEVELS...A SURFACE BOUNDARY IS
EXPECTED TO EXTEND FROM SRN GA WSWWD TO OFF THE CENTRAL AND WRN GULF
COAST.

...TX/LOWER MS VALLEY...
ALTHOUGH STRONGER UPPER FORCING IS EXPECTED TO REMAIN N OF THIS
REGION...WEAK SRN STREAM IMPULSES WILL CONTINUE TO TRAVERSE ENEWD
FROM NRN MEXICO ACROSS TX AND THE LOWER MS VALLEY. A SURFACE WAVE
IS EXPECTED TO DEVELOP ALONG THE WRN EXTENT OF THE SURFACE BOUNDARY
OVER THE NWRN GULF AND TRACK TOWARD LA. MODEL UNCERTAINTY EXISTS
WITH THE POTENTIAL FOR THIS LOW TO MOVE INLAND INTO LA/MS LATE IN
THE PERIOD. 12Z GFS/00Z ECMWF INDICATE THE LOW MOVING INTO SRN MS
BY 12Z SATURDAY.

SOME ASCENT WITH THE SRN STREAM SYSTEMS COMBINED WITH WEAK WARM
ADVECTION/ISENTROPIC LIFT WILL SUPPORT ELEVATED TSTMS ATOP A
COOL/STABLE BOUNDARY LAYER ACROSS TX INTO LOWER MS VALLEY. MODELS
SUGGEST A PORTION OF THE OFFSHORE MARINE FRONT COULD MOVE INLAND
ACROSS SERN LA/FAR SRN MS FRIDAY AFTERNOON...WITH AN INFLUX OF
MARINE BOUNDARY LAYER AIRMASS PERSISTING FRIDAY NIGHT IN RESPONSE TO
SOME INCREASE IN LOWER TROPOSPHERIC WINDS WITH DEVELOPMENT OF
SURFACE LOW. A FEW SURFACE BASED TSTMS WILL BE POSSIBLE ACROSS SRN
LA/FAR SRN MS FRIDAY AFTERNOON/NIGHT. MODEST LOW LEVEL WIND
FIELDS/POOR LAPSE RATES SHOULD PRECLUDE A SEVERE THREAT THROUGH THE
AFTERNOON. HOWEVER...MODEL SOUNDINGS SUGGEST SOME INCREASE IN
HODOGRAPH CURVATURE LATE IN THE PERIOD FOR A FEW STORMS TO BE
CAPABLE OF PRODUCING AN ISOLATED TORNADO...DESPITE THE WEAK
INSTABILITY.

FARTHER W...WEAK ELEVATED CAPE ACROSS TX MAY SUPPORT SOME HAIL
DURING THE AFTERNOON...BUT OVERALL THREAT IS EXPECTED TO REMAIN TOO
LIMITED TO SUPPORT A SEVERE THREAT WNWWD INTO TX.

..PETERS.. 03/12/2009

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