Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 170315
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
815 PM PDT WED APR 16 2014

.SYNOPSIS...
ONSHORE FLOW WILL CONTINUE TO BRING COOL TEMPERATURES TO THE AREA
THROUGH SATURDAY WITH RETURNING NIGHT THROUGH MORNING LOW CLOUDS AND
FOG. MORNING DRIZZLE IS POSSIBLE AT COASTS AND VALLEYS FRIDAY
MORNING. EXPECT WARMER WEATHER LATE IN THE WEEKEND BEFORE A TROUGH
APPROACHES ON TUESDAY BRINGING CLOUDS AND A COOLING TREND.

&&

.SHORT TERM (TONIGHT-SAT)...WEAK UPPER LEVEL TROUGH OF LOW PRESSURE
IS EXPECTED TO DEVELOP OFF THE COAST OF SOUTHERN CALIFORNIA
OVERNIGHT. THIS FEATURE COMBINED WITH STRENGTHENING ONSHORE FLOW
(LAX-DAGGETT GRADIENT CURRENTLY AT +5.7 MB) WILL LIKELY DEEPEN
THE MARINE LAYER TO AROUND 2000 FEET OR GREATER BY EARLY THURSDAY
MORNING. SATELLITE IMAGERY SHOWING LOW CLOUDS FORMING OFF THE COAST
OF LOS ANGELES COUNTY...WHICH IS EXPECTED TO EXPAND INTO MOST OF THE
COASTAL/VALLEY AREAS SOUTH OF POINT CONCEPTION OVERNIGHT INTO
THURSDAY MORNING. BY THURSDAY NIGHT...A MORE PRONOUNCED UPPER LEVEL
TROUGH DEVELOPS OFF THE CALIFORNIA COAST...WHICH WILL LIKELY
BRING AN EVEN DEEPER MARINE LAYER TO THE REGION. IN FACT...A MARINE
LAYER DEPTH OF 2500 FEET OR GREATER COULD BRING LOW CLOUDS AND FOG
ALL THE WAY INTO THE SANTA CLARITA VALLEY AND LOWER COASTAL SLOPES
BY FRIDAY MORNING. THIS ADDITIONAL DEEPENING OF THE MARINE LAYER
MAY ALSO BRING SOME PATCHY DRIZZLE TO THE REGION ON FRIDAY MORNING.
FORECASTED COOLING TREND THROUGH FRIDAY LOOKS ON TRACK DUE TO THE
DEEPENING MARINE LAYER AND STRONGER ONSHORE FLOW. THE UPPER TROUGH
WILL PASS EAST OF THE AREA SATURDAY BRINGING THE START OF A BRIEF
WARMING TREND.

*** FROM PREVIOUS DISCUSSION ***

.LONG TERM (SUN-WED)...RIDGING WILL PEAK EITHER SUNDAY OR MONDAY
WITH HIGHS WARMING UP INTO THE LOW TO MID 80S FOR THE WARMER VALLEY
AREAS. LOW CLOUDS WILL CONTINUE ALONG THE COAST DURING THE NIGHT AND
MORNING HOURS WITH COOLER TEMPS THERE. MODELS AGREE NOW THAT SOME
FORM OF TROFFING WILL DEVELOP TUE/WED. THE GFS CONTINUES TO BE THE
STRONGEST SOLUTION, THOUGH BOTH THE GFS AND ECMWF HAVE SOFTENED FROM
THEIR EARLIER EXTREMES AND NEITHER HAVE ANY MEASURABLE PRECIP FOR
OUR AREA. THE MAIN IMPACTS LIKELY WILL BE MUCH COOLER TEMPS AND AN
INCREASE IN WEST TO NORTHWEST WINDS.

&&

.AVIATION...17/0000Z.
SATELLITE IMAGERY SHOWING SOME LOW CLOUDS LINGERING OFF THE COAST
OF LA/VTU COUNTIES LATE THIS AFTERNOON. CURRENT ACARS DATA SHOWING
MARINE LAYER DEPTH AROUND 1500 FEET...BUT IS EXPECTED TO DEEPEN
TO AROUND 2000 FEET LATER TONIGHT. AS A RESULT...IFR/MVFR CIGS
EXPECTED TO RETURN TO MOST COASTAL/VALLEY TAF SITES TONIGHT...WITH
MODERATE CONFIDENCE IN ARRIVAL TIMES OF CEILINGS. THERE IS A 30 PERCENT
CHANCE OF MVFR CIGS LINGERING AT KLAX...KOXR...AND KSBA THROUGH THE
AFTERNOON HOURS ON THURSDAY.


KLAX...GOOD CONFIDENCE IN THE 00Z TAF. THERE IS GOOD CONFIDENCE
THAT BRIEF IFR CIGS COULD IMPACT KLAX THIS EVENING. AS THE MARINE
LAYER LIFTS...CIGS SHOULD GENERALLY REMAIN IN MVFR CATEGORY
LATER TONIGHT INTO THURSDAY MORNING. A 30 PERCENT CHANCE OF MVFR
CIGS LINGERING INTO THE AFTERNOON HOURS.

KBUR...GOOD CONFIDENCE IN THE 00Z TAF. IFR CONDITIONS MOVING IN
AFTER MIDNIGHT AND BECOMING MVFR AFTER SUNRISE WITH CEILINGS BURNING
OFF BY LATE MORNING.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

$$

PUBLIC...GOMBERG/MW
AVIATION...GOMBERG
SYNOPSIS...JLD

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