Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 031049
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
345 AM PDT THU SEP 3 2015

UPDATED AVIATION AND MARINE SECTION

.SYNOPSIS...

A BROAD UPPER TROUGH WILL BRING COOLER CONDITIONS TO THE REGION WITH
NIGHT THROUGH MORNING LOW CLOUDS FOR COAST AND VALLEYS THROUGH LATE
THIS WEEK. THERE WILL BE A WARMING TREND EARLY NEXT WEEK AS HIGH
PRESSURE ALOFT BUILDS IN OVER THE SOUTHERN PORTION OF THE STATE
BRINGING HIGH TEMPERATURES BACK TO NORMAL FOR THIS TIME OF YEAR.

&&

.SHORT TERM (TODAY-SAT)...LATEST AMDAR SOUNDING NEAR LAX INDICATED
THE MARINE LAYER AROUND 3500 FT THIS MORNING. FOG PRODUCT IMAGERY
WAS SHOWING LOW CLOUDS FILLING IN ACROSS MOST COAST AND VALLEY
LOCATIONS.  THE WEAK UPPER LOW THAT BROUGHT THE MID LEVEL CLOUDS TO
THE REGION YESTERDAY MORNING WAS LOCATED AROUND POINT CONCEPTION
AND IS REALLY A NON FACTOR WITH OUR WEATHER MOVING AHEAD. AS FAR AS
THIS DEEP MOIST LAYER AROUND 3500 FT...EXPECTING A SIMILAR SCOUR OUT
TIME FOR CLOUDS THIS MORNING. SKIES SHOULD BE MOSTLY SUNNY BY LATE
THIS MORNING.

SYNOPTICALLY...A BROAD UPPER TROUGH OVER THE ENTIRE WEST COAST WILL
CONTINUE TO DEEPEN AS AN UPPER LOW MOVES FROM WASHINGTON STATE INTO
NRN CALIFORNIA BY FRIDAY. ONSHORE FLOW WILL INCREASE AS WELL
BRINGING GUSTY SW WINDS THROUGH THE HIGHWAY 14 CORRIDOR AND INTO
THE ANTELOPE VALLEY WITH GUSTS TO 35 MPH LIKELY EACH AFTERNOON
THROUGH FRIDAY. OVERALL...THE RESULT WILL BE COOLER CONDITIONS AS
HIGH TEMPS CONTINUE TO LOWER A FEW DEGREES EACH DAY THROUGH FRIDAY.
THE MARINE LAYER OR DEEP MOIST LAYER WILL PERSIST AS WELL THROUGH
THE NIGHT AND MORNING HOURS. EXPECT HIGH TEMPS ACROSS THE BOARD TO
REMAIN SEVERAL DEGREES BELOW NORMAL THROUGH AT LEAST FRIDAY. HIGHS
OVER THE NEXT  IN THE VALLEYS WILL BE IN THE UPPER 70S TO LOWER 80S
WHILE COASTAL AREAS WILL REMAIN IN THE UPPER 60S AND 70S. FRIDAY
WILL BE THE COOLEST DAY OVER THE NEXT SEVERAL.

BY SATURDAY...THE CUTOFF UPPER LOW BEGINS TO FILL IN AS IT SWINGS
INTO THE INTERMOUNTAIN REGION. HEIGHTS AND THICKNESS LVLS WILL BE ON
THE RISE...WITH A SLIGHT WARM UP EXPECTED FOR MOST AREAS AFTER NIGHT
THROUGH MORNING LOW CLOUDS SCOUR OUT. THERE SHOULD BE LIMITED
STRATUS OVER THE CENTRAL COAST SATURDAY MORNING AS THE TROUGH AXIS
MOVES THROUGH. BY SATURDAY NIGHT...SOME OFFSHORE WINDS WILL DEVELOP
ACROSS THE CENTRAL COAST SATURDAY EVENING...WHICH SHOULD KEEP THE
CENTRAL COAST CLEAR AND LIMIT LOW CLOUDS TO THE LA COAST AND SAN
GABRIEL VALLEY AND POSSIBLY VENTURA COUNTY COASTAL AREAS.

.LONG TERM (SUN-WED)...

ALTHOUGH THE TROUGH AXIS WILL MOVE WELL EAST...THERE WILL CONTINUE
TO BE A WEAK TROUGH LINGERING OVER MUCH OF CALIFORNIA THROUGH
MONDAY. EXCEPT THERE WILL BE A WEAK RIDGE BUILDING IN FROM THE
SOUTHEAST AS IT EXPANDS WEST OVER THE SOUTHERN MOST PORTION OF
CALIFORNIA. THE GFS CONTINUES TO SHOW WEAK OFFSHORE FLOW DEVELOP
OVER LA/VTU COUNTIES AS WELL AS SLO COUNTY. ALTHOUGH WE ARE NOT
EXPECTING A SANTA ANA WIND EVENT...THERE WILL BE ENOUGH WEAK
OFFSHORE FLOW TO HELP WARM UP THE VALLEYS AS WELL AS THE CENTRAL
COAST WHERE NE TO E WINDS STICK AROUND INTO THE LATE MORNING HOURS.
HIGHS COULD REACH IN THE MID 80S FOR THE CENTRAL COAST SUNDAY...WITH
DECENT WARMING FOR THE LA/VTU COUNTY VALLEYS AND SOME WARMING FOR A
FEW COASTAL AREAS AS WELL. LOW CLOUDS SHOULD BE LIMITED TO THE
IMMEDIATE COAST SUNDAY MORNING BEFORE SCOURING OUT.

MON-WED THE SURFACE GRADIENTS SWITCH BACK TO WEAK-MODERATE ONSHORE
FLOW. HIGH TEMPS WILL BE A TAD COOLER OVER THE VALLEYS AND CENTRAL
COAST EARLY NEXT WEEK WHERE THE OFFSHORE FLOW HELPED WARM THESE
LOCATIONS. OTHERWISE...EXPECT A GRADUAL WARMING TREND IN MOST AREAS
EARLY NEXT WEEK...WITH HIGH TEMPS MORE AROUND NORMAL OR SLIGHTLY
HIGHER FOR THIS TIME OF YEAR.


&&

.AVIATION...AT 0815Z...THEN MARINE LAYER AT KLAX WAS ABOUT 3500 FT
DEEP. THE TOP OF THE INVERSION WAS AROUND 4500 FEET WITH A
TEMPERATURE OF 19C.

WIDESPREAD MVFR TO VFR CIGS IN ALL COASTAL AND VALLEY AREAS S OF PT
CONCEPTION...WITH CLOUDS TO THE COASTAL SLOPES. IFR CONDS WERE
OCCURRING IN THE FOOTHILLS AND ON COASTAL SLOPES. ON THE CENTRAL
COAST AND IN THE SANTA YNEZ VALLEY...CONDS WERE MOSTLY LOW MVFR.
EXPECT SKIES TO CLEAR IN MOST AREAS BY LATE MORNING. EXPECT SIMILAR
CONDS TONIGHT/FRI MORNING.

&&

.MARINE...03/300 PM. GOOD CONFIDENCE IN SCA CONDS THIS AFTERNOON
THROUGH LATE TONIGHT ACROSS THE NORTHERN TWO THIRDS OF THE
OUTER WATERS. THERE IS A 20 TO 30 PERCENT CHANCE THAT A SMALL
CRAFT ADVISORY WILL BE NEEDED FOR THE SOUTHERNMOST INNER
WATERS AND FOR THE NORTHERN INNER WATERS FOR THE SAME
TIME PERIOD.

SCA CONDS ARE EXPECTED ACROSS THE ENTIRE OUTER WATERS FRI AFTERNOON
THROUGH SAT NIGHT. THERE IS A 30 TO 40 PERCENT CHANCE THAT A SCA
WILL BE NEEDED FOR THE NORTHERN INNER WATERS DURING THE AFTERNOON
AND EVENING HOURS FRI AND SAT.

MEANWHILE...STORM FORCE WINDS IN THE SOUTH PACIFIC GENERATED A SWELL
THAT WILL AFFECT THE COASTAL WATERS OF SOUTHWEST CALIFORNIA OVER THE
WEEKEND. SWELL HEIGHTS WILL BE 2 TO 4 FEET WITH INTERVALS NEAR 20
SECONDS. MARINERS SHOULD BE PREPARED FOR LONG PERIOD SWELLS THAT
WILL LIKELY HAVE EXTRA SURGING AND CURRENTS. SHOALING IS LIKELY IN
SHALLOWER WATER AND IN SOME HARBOR ENTRANCES.

.BEACHES...LONG PERIOD SOUTH SWELL WILL LIKELY BRING ELEVATED SURF
TO SOUTH AND SOUTHWEST FACING BEACHES OVER THE HOLIDAY WEEKEND...
WITH A RATHER HIGH RISK OF DANGEROUS RIP CURRENTS EXPECTED.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
BEACH HAZARD STATEMENT (SEE LAXCFWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

$$

PUBLIC...KAPLAN
AVIATION/MARINE...DB

WWW.WEATHER.GOV/LOSANGELES



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