Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 020014 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
515 PM PDT TUE SEP 1 2015

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...SCATTERED HIGH CLOUDS ARE EXPECTED SOUTH OF POINT
CONCEPTION THROUGH WEDNESDAY. ONSHORE FLOW WILL SUPPORT MORNING
CLOUDS WITH PATCHY FOG IN SOME AREAS TO THE WEST OF THE MOUNTAINS
THROUGH THE WEEKEND. PATCHY DRIZZLE IS ALSO POSSIBLE TO THE NORTH OF
POINT CONCEPTION WEDNESDAY MORNING. BELOW NORMAL TEMPERATURES THIS
WEEK ARE EXPECTED TO REBOUND TO NEAR NORMAL BY EARLY NEXT WEEK.

&&

.SHORT TERM (TODAY-FRI)... A DEEP MARINE LAYER COMBINED WITH A WEAK
UPPER LEVEL LOW OFF THE COAST BROUGHT A HEALTHY DOSE OF COOLING TO
THE REGION TODAY. TEMPERATURES ARE CURRENTLY RUNNING 5-10 DEGREES
COOLER THAN THIS TIME YESTERDAY AND ABOUT 5 DEGREE BELOW
NORMAL...EXCEPT FOR THE COASTAL AREAS WHICH ARE SEEING LITTLE
CHANGE.

THE TROUGH WILL MOVE INTO CENTRAL CALIFORNIA ON THURSDAY...WHICH
SHOULD DEEPEN THE MARINE LAYER FURTHER AND BRING ADDITIONAL COOLING
TO THE AREA. THE DEEPENING WILL BE MOST PRONOUNCED ON THE CENTRAL
COAST DUE TO THEIR PROXIMITY TO THE UPPER LEVEL LOW`S
CIRCULATION...WHICH ALSO COULD RESULT IN A FEW SPITS OF DRIZZLE.

ONCE THE LOW PASSES THROUGH...A STRONG LOW PRESSURE SYSTEM WILL DROP
INTO WASHINGTON ON THURSDAY...WITH A LARGE TROUGH ENVELOPING THE
WEST COAST. THIS WILL BRING STEADY BUT MOSTLY UNNOTICEABLE COOLING
ON THURSDAY AND FRIDAY. MODERATELY STRONG SOUTHWESTERLY FLOW ALOFT
WILL BRING GUSTY WINDS TO THE MOUNTAINS AND INTERIOR VALLEYS...AND
SHOULD KEEP THE MARINE LAYER DEEP WITH DIFFICULT TO CALL AFTERNOON
BEHAVIOR. THE NAM COMPUTER MODEL IS SHOWING SO MUCH DEEPENING ON THE
CENTRAL COAST...THAT A CLEARING TREND COULD DEVELOP ON THURSDAY AND
FRIDAY WHICH WOULD BRING A TOUCH OF WARMING UP THERE.

.LONG TERM (SAT-TUE)... THE LARGE TROUGH PREVIOUSLY MENTIONED WILL
SWING INTO WYOMING SATURDAY AND SUNDAY. THIS SHIFT...ALONG WITH
QUICKLY WEAKENING ONSHORE FLOW...WILL ALLOW A LARGE RIDGE OF HIGH
PRESSURE CURRENTLY OVER TEXAS TO NOSE INTO CALIFORNIA AND BRING SOME
WARMING. TEMPERATURES BY SUNDAY SHOULD BE BACK TO NORMAL FOR THIS
TIME OF THE YEAR. THERE IS A POSSIBILITY OF SOME LIGHT OFFSHORE FLOW
THAT COULD ENHANCE THE WARMING OVER THE COASTAL AND VALLEY AREAS.

THE GFS AND ECMWF SOLUTIONS DIVERGE AFTER SUNDAY. THE ECMWF SHOWS
LITTLE CHANGE ON MONDAY AND TUESDAY WHEN COMPARED TO SUNDAY. THE GFS
IS CONSISTENTLY SHOWING A WEAK UPPER LEVEL LOW JUST OFF THE SOUTHERN
CALIFORNIA COAST. MOST SIGNIFICANTLY...THIS LOW WOULD BRING
SOUTHERLY FLOW TO THE AREA...WHICH ALWAYS MEANS A WINDOW OF
OPPORTUNITY FOR CLOUDS...MOISTURE...AND THUNDERSTORMS. BEING AT THE
END OF THE FORECAST WINDOW...WILL PUNT HAVING TO CHOOSE A
SOLUTION...BUT THE GFS REMAINS THE MODEL OF CHOICE BASED ON ITS
PERFORMANCE THIS YEAR.

&&

.AVIATION...02/0010Z.

AT 2308Z...THE MARINE INVERSION AT KLAX WAS AROUND 2000 FT DEEP. THE
TOP OF THE INVERSION WAS AROUND 3500 FEET WITH A TEMPERATURE OF 22
DEGREES CELSIUS.

GENERALLY HI CONFIDENCE IN THE 00Z TAFS WITH REGARD TO LOW CLOUD AND
IFR/MVFR DEVELOPMENT TONIGHT AT ALL COASTAL AND VLY AIRFIELDS WHICH
WILL PERSIST INTO LATE WED MORNING TO EARLY WED AFTERNOON...EXCEPT
AT KOXR WHERE THERE IS A 50-60 PERCENT CHANCE OF THE LOW CLOUDS
LASTING ALL DAY. 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 KWJF AND KPMD...HI CONFIDENCE IN THE 00Z TAFS WITH VFR
CONDITIONS EXPECTED THRU WED. GUSTY W TO SW WINDS AT THESE AIRFIELDS
THIS EVENING WILL DIMINISH TONIGHT AND INCREASE AGAIN WED AFTERNOON.

KLAX...GENERALLY HI CONFIDENCE IN THE 00Z TAF. LOW CLOUDS AND MVFR
CIGS ARE FORECAST TO DEVELOP BY 08Z AND PERSIST THRU 20Z WITH VFR
CIGS THRU 03Z WED EVENING BEFORE THE CIGS LOWER AGAIN TO MVFR CAT.
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 06Z AND PERSIST THRU 17Z WITH VFR
CONDITIONS THE REST OF THE DAY. THE TIMING OF THE ONSET OF THE LOW
CLOUDS TONIGHT COULD BE OFF PLUS/MINUS AN HOUR OR TWO.

&&

.MARINE...01/200PM.

OUTER WATERS... MODERATE NORTHWEST TO NORTHERLY WINDS AND AN
INCREASED SWELL WILL KEEP A SMALL CRAFT ADVISORY IN EFFECT ACROSS
THE OUTER WATERS THROUGH AT LEAST LATE TONIGHT.  THE WINDS
DIMINISHED TO BELOW CRITERIA IN SOME LOCATIONS THIS MORNING BUT WILL
INCREASE AGAIN INTO THE EVENING HOURS... AND THE SWELLS WILL
CONTINUE TO INCREASE AS WELL.  THERE IS A POTENTIAL FOR MODERATE
WINDS ACROSS THE OUTER WATERS THROUGH SATURDAY AND MARINERS SHOULD
PLAN FOR AT LEAST LOCALLY MODERATE WINDS ACROSS WESTERN PORTIONS OF
THE ZONES.

INNER WATERS... SWELLS IN THE INNER WATERS WILL INCREASE THIS
AFTERNOON AND EVENING AND THERE IS A SMALL CHANCE THAT A SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS MAY BE NEEDED OVERNIGHT.  AT THIS TIME
CONDITIONS ARE EXPECTED TO REMAIN BELOW CRITERIA BUT MARINERS SHOULD
BE PREPARED FOR LOCALLY CHOPPY CONDITIONS.

&&

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

&&
$$

PUBLIC...RK
AVIATION...SIRARD
MARINE...KJ
SYNOPSIS...RM

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