Monday, November 30, 2009

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 300659
SWODY2
SPC AC 300658

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CST MON NOV 30 2009

VALID 011200Z - 021200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
WHILE A STRONG NRN STREAM SHORT-WAVE TROUGH EXITS THE NORTHEAST/NEW
ENGLAND AND A SECOND DIGS SSEWD OUT OF THE CANADIAN PRAIRIE/NRN
ROCKIES INTO THE PLAINS...THE MORE SIGNIFICANT FEATURE WITH RESPECT
TO CONVECTIVE WEATHER WILL BE THE UPPER LOW MOVING ACROSS NRN MEXICO
EARLY IN THE PERIOD. THE CENTER OF THIS LOW IS EXPECTED TO CROSS
THE RIO GRANDE DURING THE DAY...AND THEN CONTINUE ACROSS CENTRAL TX
THROUGH THE END OF THE PERIOD.

AT THE SURFACE...CYCLOGENESIS IS PROGGED OVER THE WRN GULF...AS THE
UPPER LOW MOVES INTO/ACROSS TX. LATE IN THE PERIOD...THIS LOW
SHOULD APPROACH/MOVE INTO THE GULF COAST REGION -- AND WILL BE
ACCOMPANIED BY AT LEAST AN ISOLATED SEVERE THREAT. ELSEWHERE...A
COLD FRONT WILL MOVE SEWD ACROSS THE PLAINS IN CONJUNCTION WITH THE
DIGGING NRN STREAM TROUGH.

...TX EWD INTO CENTRAL GULF COAST REGION...
SHOWERS AND ISOLATED/ELEVATED THUNDERSTORMS WILL BE POSSIBLE ACROSS
PARTS OF SRN AND ERN TX THROUGH THE DAY...IN ZONE OF 850 TO 700 MB
WARM ADVECTION AHEAD OF THE APPROACHING UPPER SYSTEM. LIMITED
INSTABILITY WILL...HOWEVER...PRECLUDE APPRECIABLE SEVERE POTENTIAL.

HAVING SAID THAT...SEVERE THREAT IS PROGGED TO BEGIN INCREASING FROM
SRN LA EWD ACROSS SRN MS/SRN AL INTO THE FL PANHANDLE DURING THE
SECOND HALF OF THE PERIOD. HERE...SLY LOW-LEVEL FLOW AHEAD OF THE
DEVELOPING SURFACE LOW OVER THE WRN GULF WILL BRING MOIST LOW-LEVEL
GULF AIRMASS ONSHORE. ATTM...IT APPEARS THAT CONVECTION SHOULD
REMAIN ELEVATED MOST OF THE PERIOD...BUT AREAS INVOF THE CENTRAL
GULF COAST/LOWER MS VALLEY MAY EXPERIENCE SUFFICIENT BOUNDARY-LAYER
MOISTENING TO RESULT IN MINIMAL SURFACE-BASED INSTABILITY -- MAINLY
AFTER MIDNIGHT.

WHILE THE DEGREE OF INSTABILITY WILL REMAIN LIMITED...VERY STRONG
SHEAR PROFILES ARE ANTICIPATED ACROSS THIS REGION AHEAD OF THE
LOW...WITH SURFACE SELYS VEERING/INCREASING TO SSWLY AT 40 TO 60 KT
AT 850 MB...AND THEN TO SWLY AT 40 TO 60 KT AT H5. RESULTING SHEAR
PROFILES WILL BE QUITE SUPPORTIVE OF BOTH STORM ORGANIZATION AND
LOW-LEVEL ROTATION. THEREFORE...WILL INTRODUCE 5% SEVERE
PROBABILITY FROM SRN LA EWD INTO THE WRN FL PANHANDLE...TO ACCOUNT
FOR WHAT WILL LIKELY BE PRIMARILY AN ISOLATED TORNADO THREAT. WHILE
CONTINUING MODEL UNCERTAINTY WITH THE GULF LOW PRECLUDES A MORE
FOCUSED/POTENTIALLY SLIGHT RISK FORECAST ATTM...AREA MAY REQUIRE
SLIGHT RISK UPGRADE IN LATER FORECASTS AS THE SURFACE LOW EVOLUTION
AND ASSOCIATED IMPLICATIONS REGARDING THE BOUNDARY LAYER BECOME MORE
CLEAR.

..GOSS.. 11/30/2009

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