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[Printable]
537
FXUS66 KLOX 230329
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
825 PM PDT MON SEP 22 2014

.SYNOPSIS...
BUILDING HIGH PRESSURE WILL BRING A WARMING TREND AND A DECREASE IN
NIGHT THROUGH MORNING MARINE LAYER CLOUD COVERAGE THROUGH MID WEEK.
A TROUGH OF LOW PRESSURE WILL THEN BRING COOLER WEATHER AND AN
INCREASE IN NIGHT THROUGH MORNING LOW CLOUDS AND FOG FOR LATE IN THE
WEEK. OFFSHORE FLOW AND A WARMING TREND ARE POSSIBLE BY NEXT SUNDAY.

&&

.SHORT TERM (TUE-THU)...THE MARINE INVERSION WAS NEAR 900 FT DEEP AT
LAX EARLY THIS EVENING. PATCHY LOW CLOUDS WERE NOTED ALONG THE SBA
COUNTY CENTRAL COAST...AND OVER PORTIONS OF THE SOCAL BIGHT TO
AROUND PALOS VERDES. THE LOW CLOUDS ARE EXPECTED TO EXPAND OVERNIGHT
AND SPREAD ALONG THE CENTRAL COAST AND THE L.A./VTU COUNTY COAST.
LOW CLOUDS SHOULD ALSO MOVE INTO THE SANTA YNEZ VLY AND SALINAS VLY
BY LATE TONIGHT. OTHERWISE...MOSTLY CLEAR SKIES CAN BE EXPECTED
ACROSS THE REGION THRU THE NIGHT.

AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL PERSIST OVER SOCAL THRU
TUE. THE UPPER RIDGE WILL GRADUALLY MOVE E WED AND THU AS A LARGE
UPPER LEVEL TROF OVER THE E PAC APPROACHES THE REGION. VARYING
AMOUNTS OF NIGHT AND MORNING LOW CLOUDS AND FOG WILL CONTINUE TO
AFFECT THE COASTAL PLAIN AND SOME OF THE ADJACENT VLYS INCLUDING THE
SALINAS VLY THRU THU. OTHERWISE...MOSTLY CLEAR SKIES WILL CONTINUE
ALTHO A FEW MID LEVEL CLOUDS MAY MOVE INTO THE REGION WED NIGHT INTO
THU. THERE SHOULD ALSO BE SOME GUSTY S TO SW WINDS IN THE L.A./VTU
MTNS AND ANTELOPE VLY EACH AFTERNOON AND EARLY EVENING...ALTHO AN
INCREASE IN ONSHORE FLOW SHOULD BEING GUSTY NW WINDS TO THE CENTRAL
COAST FOR THU AFTERNOON AS WELL. TEMPS ACROSS THE REGION ARE
EXPECTED TO BE SEVERAL DEGREES ABOVE NORMAL FOR MANY AREAS TUE AND
WED...THEN COOL BACK TO NEAR NORMAL TO SLIGHTLY ABOVE NORMAL FOR THU.

***FROM PREVIOUS DISCUSSION***

.LONG TERM (FRI-MON)...MODELS START TO DIVERGE SOME ON FRIDAY WITH
REGARDS TO THE APPROACHING TROUGH...AS HAS BEEN THE CASE FOR SOME
TIME NOW. THE GFS IS THE FASTEST WITH THE TROUGH...THE ECMWF SLOWER
AND DEEPER...THE CANADIAN...THE EUROPEAN ENSEMBLE AND THE GFS
ENSEMBLE MEANS FALLING IN BETWEEN THE GFS AND ECMWF DETERMINISTIC
RUNS. EVEN WITH DIFFERENCES BETWEEN THE GFS AND THE EC...THE LATEST
EC DOES QUICKLY CATCH UP TO THE GFS SOLUTION BY SUNDAY AS IT KEEPS
THE TROUGH OPEN WHILE THE GFS CLOSES IT OFF AND SLOWS IT DOWN OVER
UTAH....SO OVERALL NOT AS BIG A DIFFERENCE AT IT MIGHT APPEAR. ALL
THINGS CONSIDERED...AND WITH TROUGH PASSAGE SOMETIME SATURDAY...THAT
DAY LOOKS TO BE THE COOLEST WITH HIGHS EITHER JUST BELOW NORMAL OR
5-10 DEGREES BELOW NORMAL SOME LOCATIONS. AT THIS TIME NOT EXPECTING
ANY PRECIPITATION WITH THIS SYSTEM AS IT SWINGS THROUGH...JUST NOT
ENOUGH MOISTURE TO WORK WITH. MODELS SHOW A CLEAR
FRONTAL-PRECIPITATION SIGNATURE ON THURSDAY TO OUR NORTHWEST...BUT
IT WASHES OUT AS IT MOVES EAST FRIDAY AND SATURDAY BEFORE PRODUCING
PRECIPITATION AGAIN OVER THE INTERMOUNTAIN WEST AFTER THE TROUGH
MOVES THROUGH. OUR MARINE LAYER STRATUS WILL AT LEAST THICKEN UP
WITH THIS TROUGH AND SHOULD EXTEND INTO THE INLAND VALLEYS BOTH
FRIDAY AND SATURDAY. SUNDAY SHOULD BEGIN ANOTHER WARMUP THAT GOES
INTO THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...22/2350Z...MODERATE CONFIDENCE OVERALL IN THE 00Z TAFS
DUE TO UNCERTAINTIES WITH TIMING AND EXTENT OF LOW CLOUDS TONIGHT
INTO TUE MORNING FOR MOST COASTAL AIRFIELDS AND KPRB. HOWEVER...
THERE IS GENERALLY HI CONFIDENCE THAT LOW CLOUDS AND MOSTLY IFR
CONDITIONS WILL AFFECT THESE AIRFIELDS AT TIMES DURING THE TAF
PERIOD. THE EXPECTED ONSET OF LOW CLOUDS WILL RANGE FROM 06Z AT KSMX
TO 12Z AT KPRB. THE TIMING OF THE ONSET OF THE LOW CLOUDS MAY BE OFF
PLUS/MINUS 1-2 HOURS. THE LOW CLOUDS WILL LIKELY SCATTER OUT LATE
TUE MORNING OR EARLY TUE AFTERNOON...ALTHO THERE IS ALSO UNCERTAINTY
TO THE TIMING OF THE LOW CLOUDS SCATTERING WHICH MAY BE OFF
PLUS/MINUS AN HOUR OR SO. IN ADDITION...THERE IS A 20-30 PERCENT
CHANCE THAT THE LOW CLOUDS WITH IFR/MVFR CONDITIONS MAY AFFECT KSBA
AND KBUR LATE TONIGHT AND TUE MORNING...AND A 10-20 PERCENT CHANCE
OF THIS FOR KVNY. OTHERWISE...FOR KBUR...VNY...KWJF AND KPMD THERE
IS GENERALLY HI CONFIDENCE IN VFR CONDITIONS THRU TUE.

KLAX...MODERATE CONFIDENCE OVERALL IN THE 00Z TAF DUE TO
UNCERTAINTIES WITH TIMING OF LOW CLOUDS LATE TONIGHT AND TUE
MORNING. THE LOW CLOUDS WITH IFR CIGS SHOULD DEVELOP AROUND 09Z THEN
LINGER THRU ABOUT 19Z TUE. THE TIMING OF THE ONSET AND DISSIPATION
OF THE LOW CLOUDS MAY BE OFF PLUS/MINUS 1-2 HOURS. OTHERWISE...VFR
CONDITIONS CAN BE EXPECTED AT THE AIRFIELD THRU TUE EVENING.

KBUR...GENERALLY HI CONFIDENCE IN THE 00Z TAF. VFR CONDITIONS ARE
EXPECTED THRU TUE AFTERNOON...ALTHO THERE IS A 20-30 PERCENT CHANCE
THAT LOW CLOUDS AND IFR/MVFR CIGS MAY AFFECT THE AIRFIELD LATE
TONIGHT AND TUE MORNING.

&&

.MARINE...22/800 PM...

ACROSS THE OUTER WATERS...HIGH CONFIDENCE IN LOW-END SMALL CRAFT
ADVISORY WINDS THROUGH TONIGHT. THERE IS A 40% CHANCE THAT ADVISORY
LEVEL WINDS COULD CONTINUE THROUGH THE WEEK AROUND POINT CONCEPTION
DURING THE AFTERNOON AND EVENING HOURS.

ACROSS THE INNER WATERS...HIGH CONFIDENCE IN WINDS REMAINING BELOW
ADVISORY LEVELS THROUGH THE WEEK.

A LARGE LONG-PERIOD NORTHWEST SWELL WILL MOVE INTO THE COASTAL
WATERS WEDNESDAY NIGHT...PEAK ON THURSDAY THEN LINGER THROUGH


&&

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

&&
$$

PUBLIC...SIRARD/JACKSON
AVIATION...SIRARD
MARINE...RAT/SIRARD
SYNOPSIS...KJ

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