Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 080352
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
845 PM PDT TUE JUL 7 2015

.SYNOPSIS...

A TROUGH OF LOW PRESSURE APPROACHING THE AREA WILL BRING NIGHT AND
MORNING CLOUDS...FOG AND DRIZZLE AT TIMES THROUGH THURSDAY. THERE
WILL BE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS ON WEDNESDAY
AND THURSDAY FOR THE MOUNTAINS OF SANTA BARBARA...VENTURA AND LOS
ANGELES. A COOLER AIR MASS WILL BE IN PLACE THROUGH MUCH OF THE WEEK
AS A TROUGH OF LOW PRESSURE DRIFTS OVER THE REGION. A WARMUP IS
POSSIBLE FOR THE WEEKEND AS A HIGH PRESSURE SYSTEM COULD BUILD OVER
THE AREA.

&&

.UPDATE...

WATER VAPOR IMAGERY INDICATES A CUT-OFF TROUGH OF LOW PRESSURE
CENTERED NEAR 37N AND 127W...OR ABOUT 250 MILES WEST OF THE BAY
AREA. AT THE SURFACE AND AHEAD OF THE TROUGH...MODERATE TO STRONG
ONSHORE FLOW REMAINS DRAPED OVER THE AREA THIS EVENING. ONSHORE
PRESSURE GRADIENTS SHOULD ONLY INCREASE AS THE TROUGH CENTER DROPS
INTO THE REGION OVER THE COMING DAYS. KLAX AMDAR SOUNDINGS INDICATE
THE MARINE LAYER AROUND 1900 FEET AT KLAX THIS EVENING...WHICH
AGREES WELL WITH THE LATEST NAM BUFR TIME HEIGHTS SECTIONS FOR KLAX.
IF NAM BUFR TIME HEIGHT SECTIONS PLAY OUT...THE MARINE LAYER WILL
LIKELY INCREASE TO BETWEEN 3000 AND 3500 FEET AT KLAX ON WEDNESDAY.
A DEEPENING MARINE LAYER AND STRONGER ONSHORE FLOW SHOULD ALLOW FOR
A COOLING TREND TO LINGER THROUGH AT LEAST THURSDAY.

DESPITE THE LACK OF STRATUS ON THE VISIBLE AND FOG PRODUCT IMAGERY
THIS EVENING...A MORE MATURE STRATUS DECK SHOULD DEVELOP OVER THE
COMING DAYS. DRIZZLE CERTAINLY CANNOT BE RULED OUT AS A SERIES OF
IMPULSES MOVE OVER THE REGION AND COULD SQUEEZE SOME DRIZZLE OUT OF
THE MARINE LAYER STRATUS. LOCAL 2-KM WRF SOLUTIONS OFFER SOME
CONCERN IN KEEPING MUCH OF STRATUS OUT OF THE LOS ANGELES BASIN
UNTIL LATE TONIGHT OR NEAR DAYBREAK ON WEDNESDAY...WITH BETTER
COVERAGE NORTH OF POINT CONCEPTION. AN UPDATE WILL LIKELY BE ISSUED
FOR THE MARINE LAYER COVERAGE FOR TONIGHT AND WEDNESDAY MORNING.

KSBA-KSMX SURFACE PRESSURE GRADIENTS HAVE TIGHTENED TO NEAR -3.5 MB
THIS EVENING. LOCALLY GUSTY SUNDOWNER WINDS HAVE DEVELOPED THIS
EVENING. GRADIENTS WILL BE MONITORED CLOSELY THIS EVENING FOR
ADDITIONAL DEVELOPMENT.

&&

.PREV DISCUSSION...

SHORT TERM...OVER THE NEXT FEW DAYS...WILL HAVE TO KEEP AN EYE OUT
FOR POTENTIAL ISOLATED THUNDERSTORM ACTIVITY OVER THE
MOUNTAINS...ESPECIALLY THE VENTURA COUNTY MOUNTAINS. WHILE THERE IS
FAIRLY GOOD INSTABILITY/CAPE THIS AFTERNOON OVER THE VENTURA COUNTY
MOUNTAINS...MOISTURE IS LIMITED...AND THEREFORE ONLY EXPECTING SOME
CLOUD BUILDUPS. HOWEVER...ON WEDNESDAY AND THURSDAY...THERE IS A
LITTLE MORE AVAILABLE MOISTURE DUE TO THE APPROACHING LOW. IN
ADDITION...THERE WILL BE SOME LIFT ASSOCIATED WITH THE UPPER LOW ON
THURSDAY AS IT MOVES OVER LAND. THESE FACTORS COMBINED WITH MODERATE
AFTERNOON INSTABILITY/CAPE WARRANTS THE SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS ON WEDNESDAY AND THURSDAY FOR THE MOUNTAINS (WITH
VENTURA COUNTY MOUNTAINS HAVING BEST THREAT). ON FRIDAY...THE UPPER
LOW WILL SHIFT EAST OF THE AREA AND A SLIGHT WARMING TREND WILL
BEGIN.

LONG TERM...ALL MDLS ARE IN AGREEMENT THAT A BROAD TROF WILL COVER
THE WEST COAST WHILE A LARGE UPPER HIGH WILL SIT OVER TEXAS AND NEW
MEXICO. THE FLOW ALOFT WILL REMAIN FROM THE SOUTHWEST OVER SOUTHWEST
CALIFORNIA KEEPING ANY MONSOONAL MOISTURE WELL TO THE EAST OF OUR
AREA. ONSHORE FLOW WILL CONTINUE THROUGH THE PERIOD AND THERE WILL
BE PERSISTENT NIGHT THROUGH MORNING LOW CLOUD AND FOG FOR THE COASTS
AND VLYS OTHERWISE SKIES WILL BE MOSTLY CLEAR. MAX TEMPS WILL SLOWLY
RISE THROUGH THE PERIOD AS HGTS REBOUND AND THE ONSHORE FLOW WEAKENS.

&&

.AVIATION...08/0000Z.

AT 00Z...THE MARINE LAYER DEPTH AT KLAX WAS AROUND 1900 FEET. THE
TOP OF THE INVERSION WAS AROUND 5000 FEET...WITH A TEMPERATURE OF
19 DEGREES CELSIUS.

IFR TO MVFR CONDITIONS WILL LIKELY SPREAD BACK IN THROUGH 13Z. THERE
IS A CHANCE THAT CONDITIONS COULD DETERIORATE ONE CATEGORY NORTH OF
POINT CONCEPTION OR IN DRIZZLE BETWEEN 09Z AND 16Z. TIMING OF
ARRIVAL COULD BE OFF BY UP TWO HOURS. CONDITIONS SHOULD IMPROVE VFR
BETWEEN 18Z AND 20Z...BUT THERE IS A CHANCE OF MVFR CONDITIONS OR
CEILINGS AT OR BELOW 5000 FEET LINGERING UNTIL 22Z.

KLAX...MVFR CONDITIONS AT KLAX SHOULD LINGER THROUGHOUT THE PERIOD.
THERE IS A 20 PERCENT OF CONDITIONS DROPPING INTO THE IFR CATEGORY
BETWEEN 11Z AND 16Z IN DRIZZLE. VFR CONDITIONS COULD REDEVELOP AS
SOON AS 17Z OR AS LATE AS 21Z.

KBUR...MVFR CONDITIONS SHOULD ARRIVE BETWEEN 05Z AND 08Z. THERE IS A
40 PERCENT OF CONDITIONS DROPPING INTO THE IFR CATEGORY BETWEEN 10Z
AND 16Z IN DRIZZLE. VFR CONDITIONS COULD REDEVELOP AS SOON AS 17Z OR
AS LATE AS 21Z. THERE IS A 30 PERCENT CHANCE OF MVFR CONDITIONS OR
CEILINGS AT OR BELOW 5000 FEET LINGERING UNTIL 22Z.

&&

.MARINE...07/900 PM.

SMALL CRAFT ADVISORY LEVEL WINDS WILL LIKELY DIMINISH OVERNIGHT
TONIGHT. THERE IS A 30 PERCENT CHANCE OF NORTHWEST GUSTS REACHING
SMALL CRAFT LEVELS FOR THE SOUTHERN OUTER WATERS AND THE SANTA
BARBARA CHANNEL ON WEDNESDAY AFTERNOON AND EVENING. OTHERWISE...A
DIMINISHING TREND IN THE WINDS WILL CONTINUE THROUGH MUCH OF THE
WEEK.

&&

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

&&

$$

PUBLIC...HALL/GOMBERG
AVIATION...HALL
MARINE...HALL
SYNOPSIS...SETO/HALL

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