Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 050020
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
520 PM PDT FRI SEP 4 2015

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...

MODERATE ONSHORE FLOW WILL WEAKEN OVER THE LABOR DAY
WEEKEND...LEADING TO THE RETREAT OF MORNING CLOUDS TO SOME COASTAL
LOCATIONS SUNDAY THROUGH NEXT FRIDAY. AN UPPER LEVEL HIGH BUILDING
INTO THE REGION NEXT WEEK WILL BE RESPONSIBLE FOR A GRADUAL WARMING
TREND WITH ABOVE NORMAL TEMPERATURES AWAY FROM THE COAST BY THURSDAY.

&&

.SHORT TERM (TONIGHT-MON)...OVERALL...12Z MODELS IN GOOD SYNOPTIC
AGREEMENT THROUGH THE PERIOD. AT UPPER LEVELS...LOW WILL DROP INTO
OREGON TONIGHT...THEN MOVE EAST ON SATURDAY AS WEAK TROUGHING
REMAINS OVER CALIFORNIA. NEAR THE SURFACE...MODERATE ONSHORE FLOW
WILL GRADUALLY WEAKEN THROUGH SATURDAY...TURNING WEAKLY OFFSHORE ON
SUNDAY...THEN BACK WEAKLY ONSHORE ON MONDAY.

FORECAST-WISE...NO DRAMATIC CHANGES TO PREVIOUS FORECAST THINKING.
STILL NO SIGNIFICANT MID-LEVEL MOISTURE INDICATED BY THE MODELS...SO
SKIES INLAND SHOULD REMAIN MOSTLY CLEAR THROUGH MONDAY. HOWEVER
ACROSS THE COASTAL PLAIN/VALLEYS...THE MARINE LAYER WILL CONTINUE TO
BE THE MAIN CHALLENGE. WITH SLIGHT H5 HEIGHT RISES TONIGHT...THE
MARINE INVERSION SHOULD BECOME A BIT MORE SHALLOW...BUT STILL PLENTY
DEEP ENOUGH TO PUSH WELL INLAND TONIGHT/SATURDAY MORNING...BEFORE
DISSIPATING SATURDAY AFTERNOON. FOR SATURDAY NIGHT/SUNDAY...THE WEAK
OFFSHORE FLOW AND FURTHER H5 HEIGHTS RISES IS EXPECTED TO LIMIT
STRATUS TO SOUTHERLY LOS ANGELES COUNTY. BY SUNDAY NIGHT AND
MONDAY...THE STRATUS SHOULD BE A BIT MORE WIDESPREAD REACHING UP TO
THE VENTURA COUNTY COAST...AND DEVELOPING OVER THE CENTRAL COAST.

AS FOR WINDS...MODERATE ONSHORE WINDS WILL CONTINUE ACROSS THE AREA
THROUGH SATURDAY WITH THE USUAL GUSTY AFTERNOON/EVENING WINDS ACROSS
THE MOUNTAINS AND DESERTS. ON SUNDAY...THE UPPER SUPPORT FOR
OFFSHORE WINDS IS NEGLIGIBLE...SO WILL ONLY ANTICIPATE LOCALIZED
NORTHEAST WINDS SUNDAY MORNING THAT WILL BE WELL BELOW ADVISORY
LEVELS. ON MONDAY...THE ONSHORE WINDS WILL REESTABLISH THEMSELVES
BUT REMAIN ON THE WEAK SIDE.

AS FOR TEMPERATURES...SATURDAY SHOULD GENERALLY BE 3-6 DEGREES
WARMER THAN TODAY. ON SUNDAY...THE WEAK OFFSHORE FLOW WILL REALLY
HELP BOOST TEMPERATURES...WITH AREAS AWAY FROM THE COAST IN THE MID
80S TO MID 90S. ON MONDAY...ONLY MINOR FLUCTUATIONS ANTICIPATED

THE ECMWF DOES HINT AT SOME MID-LEVEL MOISTURE MOVING INTO FAR
SOUTHERN CALIFORNIA ...A
BIT WARMER INLAND AND A BIT COOLER NEAR THE COAST.

.LONG TERM (TUE-FRI)...OVERALL...12Z MODELS CONTINUE TO EXHIBIT GOOD
SYNOPTIC AGREEMENT. AT UPPER LEVELS...TROUGH WILL REMAIN OVER THE
AREA ON TUESDAY...THEN A RIDGE WILL BUILD OVER THE AREA WEDNESDAY
THROUGH FRIDAY. NEAR THE SURFACE...WEAK DIURNAL FLOW LOOKS TO
PREVAIL WITH WEAK OFFSHORE AT NIGHT AND WEAK ONSHORE DURING THE DAY.

FORECAST-WISE...TUESDAY SHOULD BE VERY SIMILAR TO MONDAY WITH REGARD
TO STRATUS COVERAGE AND TEMPERATURES. FOR WEDNESDAY THROUGH FRIDAY A
WARMING TREND WILL ENSUE AS UPPER RIDGE BUILDS OVERHEAD AND MARINE
LAYER STRATUS IS LIMITED TO THE COASTAL PLAIN. IN FACT BY THURSDAY
AND FRIDAY...MOST VALLEY AREAS WILL EXPERIENCE HIGH TEMPERATURES IN
THE 90S.

&&

.AVIATION...05/0015Z.

AT 2309Z...THE MARINE INVERSION AT KLAX WAS AROUND 2700 FT DEEP. THE
TOP OF THE INVERSION WAS AROUND 5700 FEET WITH A TEMPERATURE OF 16
DEGREES CELSIUS.

GENERALLY HI CONFIDENCE IN THE 00Z TAFS WITH REGARD TO LOW CLOUD AND
MVFR CIGS DEVELOPING TONIGHT AT ALL COASTAL AND ADJACENT VLY
AIRFIELDS. THE CLOUDS WILL IMPROVE TO VFR CIGS AT MOST AIRFIELDS
EARLY SAT MORNING THEN LINGER INTO LATE SAT MORNING TO EARLY SAT
AFTERNOON BEFORE CLEARING. THERE IS MODERATE CONFIDENCE IN THE
TIMING OF THE ONSET OF THE LOW CLOUDS WHICH COULD BE OFF PLUS/MINUS
AN HOUR OR TWO. FOR KPMD...KWJF AND KPMD...HI CONFIDENCE IN THE 00Z
TAFS WITH VFR CONDITIONS EXPECTED THRU SAT. AT KWJF AND KPMD...GUSTY
W TO SW WINDS THIS EVENING WILL DIMINISH TONIGHT AND INCREASE AGAIN
SAT AFTERNOON. GUSTY NW WINDS ARE ALSO EXPECTED AT KSBP AND KSMX
EARLY THIS EVENING.

KLAX...GENERALLY HI CONFIDENCE IN THE 00Z TAF. LOW CLOUDS AND MVFR
CIGS ARE FORECAST TO DEVELOP BY 07Z TONIGHT...IMPROVE TO VFR CIGS BY
16Z SAT THEN SCATTER OUT BY 21Z. VFR CONDITIONS WILL THEN PERSIST
THRU SAT EVENING. THE TIMING OF THE ONSET OF THE LOW CLOUDS TONIGHT
COULD BE OFF PLUS/MINUS AN HOUR OR TWO.

KBUR...GENERALLY HI CONFIDENCE IN THE 00Z TAF. LOW CLOUDS AND MVFR
CIGS ARE FORECAST TO DEVELOP BY 07Z TONIGHT...IMPROVE TO VFR CIGS BY
16Z SAT THEN CLEAR BY 20Z. VFR CONDITIONS WILL THEN PERSIST THRU SAT
AFTERNOON. THE TIMING OF THE ONSET OF THE LOW CLOUDS TONIGHT COULD
BE OFF PLUS/MINUS AN HOUR OR TWO.

&&

.MARINE...04/200 PM.

SMALL CRAFT ADVISORY CONDITIONS FOR NORTHWEST WINDS WILL VERY LIKELY
PERSIST FROM PIEDRAS BLANCAS TO SAN NICOLAS ISLAND INCLUDING THE 0-
10 NM FROM PIEDRAS TO POINT SAL THROUGH EARLY SATURDAY MORNING.
THERE IS A CHANCE THE SCA CONDITIONS WILL CONTINUE THROUGH SUNDAY
MORNING.  A 20 SECOND PERIOD OR GREATER SOUTH SWELL IS EXPECTED TO
BUILD THROUGH THE WEEKEND TO 3 TO 4 FEET AND THEN PERSIST THROUGH
EARLY NEXT WEEK. THE LONG PERIOD SWELLS WILL LIKELY GENERATE EXTRA
SURGING AND CURRENTS WHICH MAY BE HAZARDOUS TO ANCHORED BOATS.


.BEACHES...BEACHGOERS SHOULD BE AWARE OF POTENTIALLY HAZARDOUS SURF
ALONG EXPOSED SOUTH AND SOUTHWEST FACING SHORES THIS WEEKEND THROUGH
NEXT TUESDAY. AN INCREASING RISK OF RIP CURRENTS IS EXPECTED
STARTING THIS AFTERNOON AS THE LONG PERIOD SWELL BEGINS TO
ARRIVE...AND IT IS EXPECTED THAT A HIGH RIP CURRENT RISK WILL BE
ISSUED SUNDAY THROUGH TUESDAY.

&&

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

&&

$$

PUBLIC...RAT
AVIATION...SIRARD
MARINE...30
SYNOPSIS...RM

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