Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 271247
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
345 AM PST FRI FEB 27 2015

UPDATED AVIATION SECTION

.SYNOPSIS...

A WEATHER PATTERN CHANGE WILL BEGIN TONIGHT AS THERE WILL BE PERIODS
OF RAIN THROUGH EARLY NEXT WEEK WITH LOWER SNOW LEVELS EXPECTED
ACROSS MOUNTAIN LOCATIONS...POSSIBLY AFFECTING THE INTERSTATE 5
CORRIDOR SATURDAY THROUGH MONDAY. TEMPERATURES WILL BE BELOW NORMAL
AS WELL THROUGH EARLY NEXT WEEK.

&&

.SHORT TERM (TODAY-SUN)...LATEST FOG PRODUCT IMAGERY INDICATED LOW
CLOUDS ACROSS THE CENTRAL COAST AND DEVELOPING ACROSS THE L.A.
COUNTY BASIN AND INTO THE SAN GABRIEL VALLEY AND ADJACENT COASTAL
SLOPES. LOW CLOUDS SHOULD SPREAD INTO THE SAN FERNANDO VALLEY BY
DAWN AND PORTIONS OF THE VENTURA COUNTY COAST AND VALLEYS...BUT
MIGHT HAVE A TOUGH TIME MAKING IT INTO THE SANTA CLARITA VALLEY AS
NORTHERLY WINDS HAVE PERSISTED ACROSS THE I-5 CORRIDOR THIS MORNING.
LATEST ACARS SOUNDING NEAR LAX INDICATED A WEAK INVERSION FROM 1300
FT UP TO 2500 FT. WITH THE INVERSION BEING SO WEAK AND INCREASING
ONSHORE FLOW TODAY...EXPECT LOW CLOUDS TO CONTINUE TO INCREASE
ACROSS MUCH OF LA/VTU COUNTIES LATER THIS MORNING WITH SKIES
BECOMING PARTLY TO MOSTLY CLOUDY TODAY.

A WIND ADVISORY HAS BEEN ISSUED FOR THE SANTA BARBARA COUNTY
MOUNTAINS AND ADJACENT WIND PRONE AREAS ACROSS THE SOUTH COAST OF
SANTA BARBARA FOR GUSTY NW WINDS LATE THIS AFTERNOON THROUGH THIS
EVENING. STRONGEST WIND GUSTS WILL BE BETWEEN 35 AND 45 MPH. THERE
WILL BE GUSTY SW TO W WINDS ACROSS THE ANTELOPE VALLEY AS WELL THIS
AFTERNOON...BUT SHOULD REMAIN JUST BELOW WIND ADVISORY THRESHOLDS.
EXPECT LOCAL GUSTS TO 45 MPH IN SOME LOCATIONS.

SYNOPTICALLY...AN UPPER LEVEL LOW THAT WAS OVER WASHINGTON STATE
THIS MORNING WILL CONTINUE TO TREK SOUTH TOWARDS NORTHERN CALIFORNIA
THIS AFTERNOON. THIS UPPER LEVEL FEATURE WILL THEN MOVE SLOWLY TO
THE SOUTH AND BECOME CUTOFF LATE SATURDAY INTO SUNDAY OVER SOUTHERN
CALIFORNIA...THEN PUSH OUT OF THE AREA BY MONDAY MORNING...AS
ANOTHER UPPER LEVEL DISTURBANCE QUICKLY MOVES IN BEHIND THE EXITING
LOW. THIS WEATHER PATTERN WILL BRING AN EXTENDED PERIOD OF SHOWERS
ACROSS MUCH OF SOUTHWESTERN CALIFORNIA...WITH SNOW SHOWERS IN THE
MOUNTAINS. AS HAS BEEN THE CASE OVER THE PAST SEVERAL STORM
EVENTS...THE UPPER LOWS HAVE BEEN MAINLY OVER LAND AS THEY
RETROGRADED TOWARDS SOUTHERN CALIFORNIA. MOST OF THE SYSTEMS HAVE
HAD A TOUGH TIME TAPPING INTO SOME MOISTURE DUE TO THEIR TRAJECTORY.
HOWEVER...MOST MODELS ARE NOW BRINGING THIS UPPER LOW A TAD FARTHER
WEST OVER THE COASTAL WATERS AS IT REACHES SOUTHERN CALIFORNIA WHICH
SHOULD HELP TO TAP INTO SOME ADDITIONAL MOISTURE. OVERALL...AREAS TO
OUR SOUTH WILL LIKELY SEE THE BETTER PRECIP AMOUNTS DUE TO BEST
CYCLONIC FLOW AROUND THE LOW. THAT BEING SAID...MODELS ARE IN PRETTY
GOOD AGREEMENT WITH THE STORM TRACK...BUT ARE STILL QUITE VARIED
WITH PRECIP AMOUNTS.

AT THIS POINT...WILL STAY WITH WINTER STORM WATCH HOPING THAT NEXT
SET OF MODELS WILL BE A BIT CLEARER AND THE DAY SHIFT CAN MAKE A
BETTER EDUCATED DECISION TO EITHER UPGRADE THE WATCH TO A WINTER
STORM WARNING OR WINTER WEATHER ADVISORY. THE FACT THAT THERE IS NOT
AN ORGANIZED COLD FRONT BRINGING A STEADY PERIOD OF RAIN OVER THE
REGION MAKES THE FORECAST A BIT DIFFICULT. RAINFALL TOTALS WILL VARY
WITH THIS NEXT SYSTEM. THERE WILL BE PLENTY OF COLD AIR ASSOCIATED
WITH THE UPPER LOW TO HELP CAUSE THE ATMOSPHERE TO BECOME UNSTABLE
ON SATURDAY AND BRING A SLIGHT CHANCE OF THUNDERSTORMS TO AREAS N OF
VENTURA COUNTY. AS THE UPPER LOW MOVES FARTHER SOUTH...THE ENTIRE
FORECAST AREA FROM SLO TO LA COUNTIES WILL HAVE A SLIGHT CHANCE OF
THUNDERSTORMS INCLUDING THE ADJACENT COASTAL WATERS. EXPECT MOSTLY
SHOWERY CONDITIONS FROM LATE TONIGHT THROUGH SUNDAY. PRELIMINARY
RAINFALL TOTALS CURRENTLY ARE FORECAST BETWEEN 0.10 AND 0.50
INCHES...WITH UP TO 1.25 INCH IN THE SAN GABRIEL MOUNTAINS. THERE
COULD BE HIGHER AMOUNTS NEAR THUNDERSTORMS.

ONE OF THE MAIN IMPACTS WITH THIS NEXT SYSTEM WILL BE THE LOWER SNOW
LEVELS POSSIBLY AFFECTING THE I-5 CORRIDOR AND HIGHWAY 14.SNOW
LEVELS WITH THIS SYSTEM WILL BE MUCH LOWER THAN THE LAST.
INITIALLY...SNOW LEVELS WILL BE AROUND 6500 FT TONIGHT...THEN LOWER
TO BETWEEN 4500 AND 5000 FEET BY SATURDAY AFTERNOON. SNOW LEVELS
WILL DROP FURTHER BY SATURDAY NIGHT INTO SUNDAY DOWN TO BETWEEN 3500
AND 4000 FT. AT THIS TIME IT LOOKS LIKE SNOW AMOUNTS WILL BE BETWEEN
6 AND 12 INCHES FOR THE LA/VTU/SBA MOUNTAINS ABOVE 5500 FT...WITH
LESSER AMOUNTS BELOW. THE I-5 CORRIDOR COULD BE AFFECTED WITH SNOW
AND ICY CONDS BY LATE SATURDAY AFTERNOON THROUGH MONDAY.

AS FAR AS TEMPS GO OVER THE NEXT FEW DAYS...IT WILL BE MUCH COOLER
WITH MOST AREAS WEST OF THE MOUNTAINS IN THE UPPER 50S TO MID 60S.
OF COURSE IT WILL BE MUCH COLDER ACROSS THE MOUNTAINS AND INTERIOR
LOCATIONS. THE COLDEST DAY LOOKS TO BE SUNDAY.

.LONG TERM (MON-THU)...THE UPPER TROUGH AXIS WILL BE JUST SOUTH OF
THE AREA MONDAY...BUT THERE WILL BE LINGERING SHOWERS ACROSS THE
FORECAST AREA...ESPECIALLY FOR AREAS S OF POINT CONCEPTION.
HOWEVER...ANOTHER SHORT WAVE DISTURBANCE IS POISED TO MOVE IN OVER
THE FORECAST AREA BY MONDAY NIGHT INTO TUE MORNING. THIS WILL ALLOW
FOR SOME ADDITIONAL SHOWERS TO OCCUR WITH CONTINUED COLDER THAN
NORMAL TEMPS ON TUESDAY. EXCEPT FOR A FEW LINGERING CLOUDS AROUND
THE MOUNTAINS...SKIES SHOULD BE MOSTLY CLEAR...WITH WEAK OFFSHORE
FLOW FOR INTERIOR AREAS BOTH WED/THU. WARMEST DAY WILL BE THURDAY
FOR COAST AND VALLEYS WITH HIGHS IN THE LOWER 70S.


&&

.AVIATION...27/1145Z.

AT 0910Z...THE MARINE LAYER AT KLAX WAS 1500 FEET DEEP...THE TOP
OF THE INVERSION WAS LOCATED AT 2400 FT WITH A TEMP OF 13C.

LOW CLOUDS REALLY EXPANDING IN COVERAGE ACROSS THE FCST AREA EARLY
THIS MORNING. CONDITIONS MOSTLY MVFR ACROSS COASTAL SXNS OF L.A. AND
VTU COUNTIES...HIGH IFR IN THE VLYS...AND LIFR/VLIFR ON THE CENTRAL
COAST AND IN THE SANTA YNEZ VALLEY. CIGS SHOULD CONT TO RISE...
ESPECIALLY S OF PT CONCEPTION THIS MORNING. EXPECT SLOW CLEARING
NEAR THE COAST...WITH CLOUDS POSSIBLY LINGERING INTO THE AFTERNOON.
EXPECT WIDESPREAD MVFR CIGS TO RETURN TO ALL AREAS WEST OF THE MTNS
THIS EVENING...POSSIBLY EVEN INTO THE ANTELOPE VLY. THERE IS A
CHANCE OF RAIN N OF PT CONCEPTION AFTER MIDNIGHT...WITH SOME DRIZZLE
POSSIBLE S OF PT CONCEPTION. GUSTY WINDS THRU AND BELOW PASSES AND
CANYONS OF SRN SBA COUNTY THIS EVENING WITH LLWS AND MDT UDDF.


KLAX...MODERATE CONFIDENCE IN THE 12Z TAF. THERE IS A 20 TO 30
PERCENT CHANCE THAT MVFR CIGS WILL LINGER THROUGH THE DAY.


KBUR...MODERATE CONFIDENCE IN THE 12Z TAF. THERE IS A 20 TO 30
PERCENT CHANCE THAT CIGS WILL BE IN THE IFR CATEGORY BETWEEN 12Z AND
17Z.

&&

.MARINE...27/330 AM...

FOR THE OUTER WATERS...HIGH CONFIDENCE IN THE FORCE NORTHWEST WINDS
THROUGH TONIGHT...EXCEPT DIMINISHING BELOW GALE FORCE TO SCA LEVELS
ACROSS NORTHERN SECTIONS THIS EVENING. SCA CONDS ARE EXPECTED ACROSS
THE SOUTHERN TWO OUTER WATERS ZONES SAT.

FOR THE INNER WATERS...GOOD CONFIDENCE IN SCA LEVEL WINDS ACROSS THE
NORTHERN INNER WATERS THIS AFTERNOON THROUGH THIS EVENING...AND
ACROSS THE SANTA BARBARA CHANNEL AND SOUTHERN INNER WATERS FROM LATE
THIS AFTERNOON THROUGH MID MORNING SAT. THERE IS A 20 PERCENT CHANCE
OF GALE FORCE WINDS ACROSS WESTERN PORTIONS OF THESE ZONES
TONIGHT.

SHOWERS ARE EXPECTED ACROSS THE WATERS THIS WEEKEND. FROM SATURDAY
AFTERNOON THROUGH SUNDAY EVENING...THERE IS A SLIGHT CHANCE OF
THUNDERSTORMS WHICH COULD PRODUCE GUSTY WINDS...CHOPPY SEAS...AND
POSSIBLY AN ISOLATED WATERSPOUT.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH (SEE LAXWSWLOX).
WIND ADVISORY (SEE LAXNPWLOX).
GALE WARNING (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).

&&

$$

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

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