ACUS01 KWNS 030457
SWODY1
SPC AC 030454
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1154 PM CDT THU OCT 02 2008
VALID 031200Z - 041200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
EARLY STAGES OF SIGNIFICANT UPPER AIR PATTERN EVOLUTION FCST THROUGH
PERIOD. STG SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY INVOF 45N139W -- MAY EVOLVE INTO CLOSED LOW BEFORE MOVING
INLAND BC/WA COASTS AROUND OR SHORTLY AFTER END OF PERIOD.
LONG-FETCH 110-150 KT JET...ON BACK SIDE OF ASSOCIATED NEGATIVELY
TILTED SYNOPTIC-SCALE TROUGHING...WILL BEGIN TO IMPINGE ON PACIFIC
COAST LATE IN PERIOD. AS THIS OCCURS...WIDESPREAD HEIGHT FALLS ARE
FCST ACROSS CONUS FROM ROCKIES WWD...ALONG WITH GEN COOLING ALOFT
WITH TIME. AS FLOW STRENGTHENS ACROSS ROCKIES...EXPECT MORE
VIGOROUS LEE TROUGHING AND LOW LEVEL WAA ACROSS MUCH OF PLAINS
STATES. MEANWHILE...PERSISTENT UPPER LOW PRESENTLY OVER NERN ONT
AND WRN QUE IS EXPECTED TO REDEVELOP NEWD ACROSS
LABRADOR...WEAKENING UPPER JET SOMEWHAT ACROSS GREAT LAKES REGION.
AT SFC...LEE TROUGHING IS FCST OVER HIGH PLAINS FROM MT-NM.
CORRIDOR OF WARM FRONTOGENESIS IS FCST FROM S-CENTRAL HIGH PLAINS
ESEWD ACROSS NRN TX AND SRN OK ESEWD ACROSS MS DELTA REGION.
QUASISTATIONARY/WEAK FRONTAL ZONE WILL PERSIST ACROSS CENTRAL/SRN
FL...SUPPORTING AT LEAST MRGL POTENTIAL FOR GEN THUNDER IN
COMBINATION WITH ADEQUATE LOW LEVEL MOISTURE AND MESOSCALE SEA/LAND
BREEZE BOUNDARIES.
...CENTRAL TX TO OZARKS...
THIS AREA REPRESENTS SPATIAL OVERLAP OF TWO TEMPORALLY DISTINCT
REGIMES...
1. HIGHLY CONDITIONAL/DIURNAL TSTM POTENTIAL INVOF DEVELOPING WARM
FRONTAL ZONE OVER CENTRAL/NRN TX AND PERHAPS SRN OK. OPERATIONAL
NAM -- TYPICALLY MOST AGGRESSIVE OF DETERMINISTIC MODELS WITH
EARLY-STAGE MOISTURE RETURN -- FCSTS DEVELOPMENT OF THUNDER INVOF
CENTRAL/NRN TX WARM FRONT. SO ARE A FEW SREF MEMBERS.
HOWEVER...STG ELEVATED MIXED LAYER OVERHEAD...AND ASSOCIATED
CAPPING...MAY PRECLUDE CONVECTIVE DEVELOPMENT ALTOGETHER...WHICH IS
INDICATED BY OTHER SREF MEMBERS AND OPERATIONAL SPECTRAL. MODIFIED
FCST SOUNDINGS SUGGEST VERY WEAK CINH DURING BRIEF LATE AFTERNOON
TIME WINDOW WHEN BOUNDARY LAYER IS WARMEST AND BEST MIXED.
2. NOCTURNAL/ELEVATED TSTM RISK FROM ERN OK INTO OZARKS...WHICH
APPEARS MORE CERTAIN ATTM. POTENTIAL FOR ISENTROPIC LIFT OF PARCELS
TO LFC WILL INCREASE AS ASSOCIATED TRAJECTORIES PROGRESSIVELY
MOISTEN OVERNIGHT...INVOF NOSE OF 40-50 KT LLJ. STG VEERING WITH
HEIGHT IS FCST IN WAA REGIME...BUT NOT NECESSARILY THROUGH DEPTH
COVERING EFFECTIVE INFLOW BASE THROUGH MOST OF BUOYANT
LAYER...BECAUSE OF RELATIVELY WEAK MID-UPPER LEVEL FLOW. WHILE
ISOLATED HAIL CANNOT BE RULED OUT...ELEVATED CAPE/SHEAR COMBINATION
APPEARS TOO WEAK ATTM TO DRAW SVR PROBABILITIES AOA 5-PERCENT.
...WRN CONUS...
WIDELY SCATTERED TSTMS ARE POSSIBLE ACROSS VERY BROAD SWATH OF WRN
CONUS FROM SRN ROCKIES TO NRN ROCKIES...ERN GREAT BASIN AND PACIFIC
NW. GREAT MAJORITY OF THIS CONVECTION WILL BE DIURNALLY FORCED AS
HEATING OF HIGHER TERRAIN OVERCOMES WEAK CINH...BENEATH FAVORABLY
STEEP MIDLEVEL LAPSE RATES CAUSED BY LARGE SCALE ASCENT/COOLING.
FRAGMENTED AREAS OF MLCAPES 100-400 J/KG ARE EXPECTED. STG SFC
COOLING OF HIGHER ELEVATIONS AFTER SUNSET WILL REMOVE SFC-BASED
THUNDER THREAT QUICKLY...HOWEVER POCKETS OF ENHANCED LARGE SCALE
ASCENT MAY SUPPORT ISOLATED/SPORADIC NOCTURNAL THUNDER WITH MUCAPES
AOB 100 J/KG.
..EDWARDS/HURLBUT.. 10/03/2008
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