DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 170727
SWODY3
SPC AC 170726

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0226 AM CDT MON SEP 17 2012

VALID 191200Z - 201200Z

...SYNOPSIS...
IN MID-UPPER LEVELS...MEAN TROUGHING WILL REMAIN IN PLACE FROM
HUDSON BAY TO CENTRAL GULF OF MEXICO THROUGHOUT PERIOD.
HOWEVER...GEOMETRY OF HEIGHT PATTERN WILL SHIFT AS NRN-STREAM
SHORTWAVE DISCUSSED IN DAY-2 OUTLOOK DEPARTS NEWD ALONG ST. LAWRENCE
RIVER AND SERN QUE. MEANWHILE...WEAKER SHORTWAVE TROUGH WILL MOVE
SEWD FROM NRN PLAINS TO MS/AL...WHILE ANOTHER SMALL PERTURBATION
CROSSES PORTIONS NRN MN...UPPER MI AND LS. SFC COLD FRONT IS FCST
FROM MAINE TO OUTER BANKS...COASTAL GA AREA AND NERN/CENTRAL GULF.
FRONT SHOULD DECELERATE CONSIDERABLY AND WEAKEN ACROSS NRN FL
PENINSULA DURING PERIOD...WHERE WEAKENING OF CONVERGENCE AND
SHEAR...ALONG WITH SMALL LAPSE RATES ALOFT...INDICATE MINIMAL SVR
THREAT. ANOTHER SFC COLD FRONT SHOULD MOVE SEWD OUT OF DAKOTAS
EARLY IN PERIOD...REACHING WRN WI...IA...SERN NEB AND SWRN KS BY
20/00Z.

...CENTRAL/ERN MAINE...EARLY PERIOD...
NARROW BAND OF NEAR-FRONTAL CONVECTION MAY SWEEP EWD ACROSS THIS
AREA DURING MORNING...AS EXTENSION OF DAY-1 REGIME...AND STG GUSTS
CANNOT BE RULED OUT. ATTM...LACK OF INSTABILITY AND SOME
UNCERTAINTIES ON FRONTAL TIMING PRECLUDE UNCONDITIONAL SVR
PROBABILITIES. FCST SOUNDINGS SUGGEST LIFTED PARCELS WILL ORIGINATE
ABOVE SLIGHTLY ELEVATED STABLE LAYER FOR ALL BUT SLOWEST FROPA
SCENARIOS. GIVEN STRENGTH OF PREFRONTAL WIND FIELDS...HOWEVER...AT
LEAST MRGL SVR PROBABILITIES MAY BE INTRODUCED IN FUTURE
OUTLOOKS...GIVEN MORE CONFIDENCE THAT NEUTRALLY TO WEAKLY UNSTABLE
THERMODYNAMIC PROFILES WILL SUPPORT DAMAGING-WIND THREAT IN FIRST
FEW HOURS OF PERIOD.

...TX PANHANDLE...WRN OK...
NARROW PLUME OF MRGL MOISTURE -- WITH SFC DEW POINTS GENERALLY 50S F
-- SHOULD ADVECT NEWD FROM SW TX ACROSS THIS REGION DURING
AFTERNOON/EVENING. THIS MAY SUPPORT ISOLATED TO WIDELY SCATTERED
TSTM DEVELOPMENT ALONG PREFRONTAL CONFLUENCE LINE...IN ENVIRONMENT
CHARACTERIZED BY STG DEEP-LAYER DIRECTIONAL SHEAR AND WELL-MIXED
SUBCLOUD LAYER. LACK OF RICHER MOISTURE WILL LIMIT
BUOYANCY...HOWEVER...WITH MODIFIED SOUNDINGS SHOWING LESS THAN 750
J/KG MLCAPE MOST AREAS. SVR WIND/HAIL RISK...IF ANY...WOULD BE
SHORT-LIVED AND APPEARS TOO MEAGER FOR 5% UNCONDITIONAL LINE ATTM.

..EDWARDS.. 09/17/2012

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