Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 031631
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
930 AM PDT SUN MAY 3 2015

.SYNOPSIS...
NIGHT THROUGH MORNING LOW CLOUDS AND FOG WILL CONTINUE THROUGH
MIDWEEK WITH ONSHORE FLOW AND WEAK LOW PRESSURE. ANOTHER LOW WILL
MOVE IN THURSDAY WITH POSSIBLE RAIN SHOWERS INTO THE END OF THE
WEEK. THE TEMPERATURES SHOULD REMAIN BELOW NORMAL ALL WEEK LONG.

&&

.SHORT TERM (TODAY-WED)...
WEAK TROUGH OF LOW PRESSURE OFF THE COAST OF SOUTHERN CALIFORNIA
WILL CONTINUE TO SLOWLY TRACK EASTWARD TODAY...WITH THE LOW
BECOMING CENTERED JUST OFF OF POINT CONCEPTION BY THIS EVENING.
MEANWHILE...PRESSURE GRADIENTS ARE TRENDING ONSHORE WITH CURRENT
LAX-DAGGETT GRADIENT AT +4.2 MB. THE COMBINATION OF THE UPPER LOW
AND STRENGTHENING ONSHORE FLOW BROUGHT A DEEPENING MARINE
LAYER THIS MORNING...WITH LATEST ACARS SOUNDING SHOWING A DEPTH
AROUND 2500 FEET OVER THE LA BASIN. AS A RESULT...LOW CLOUDS
SPREAD WELL INLAND INTO MOST VALLEY AREAS THIS MORNING. WHILE MOST
OF THE LOW CLOUDS ARE EXPECTED TO BURN OFF THIS AFTERNOON...THERE
WILL LIKELY BE SOME LOW CLOUDS LINGERING NEAR SOME IMMEDIATE COASTAL
AREAS. THE INCREASING ONSHORE FLOW AND MARINE LAYER INFLUENCE WILL
BRING SIGNIFICANT COOLING TO THE REGION TODAY...WITH VALLEY AREAS
GENERALLY REMAINING IN THE 70S. ONSHORE FLOW WILL CONTINUE TO
INCREASE THIS AFTERNOON...WITH A PROJECTED LAX-DAGGETT GRADIENT OF
AROUND +8 MB...RESULTING IN GUSTY ONSHORE WINDS ACROSS THE MOUNTAINS
AND ANTELOPE VALLEY...WHERE GUSTS BETWEEN 30 AND 40 MPH CAN
GENERALLY BE EXPECTED. ISOLATED WIND GUSTS AS HIGH AS 50 MPH CAN BE
EXPECTED NEAR LAKE PALMDALE. WITH SOME INCREASING
INSTABILITY...SHOULD SEE SOME CUMULUS BUILDUPS OVER THE LOCAL
MOUNTAINS THIS AFTERNOON AND AGAIN MONDAY AFTERNOON. HOWEVER
NO SHOWERS OR THUNDERSTORMS ARE EXPECTED DUE TO THE VERY LIMITED
AVAILABLE MOISTURE.

AS THE WEAK UPPER LEVEL LOW PRESSURE SYSTEM MOVES OVER SOUTHERN
CALIFORNIA OVERNIGHT...THERE WILL LIKELY BE ADDITIONAL DEEPENING
OF THE MARINE LAYER TO AROUND 3000 FEET...WITH LITTLE CHANGE INTO
TUESDAY. AS A RESULT...COULD SEE SOME LOW CLOUDS AND FOG REACHING
INTO THE LOWER COASTAL SLOPES ALONG WITH SOME PATCHY DRIZZLE THE
NEXT COUPLE OF DAYS. THE COOLING TREND WILL CONTINUE...ALONG WITH
THE GUSTY ONSHORE WINDS IN THE MOUNTAINS AND ANTELOPE VALLEY.

*** FROM PREVIOUS DISCUSSION ***

BROAD TROFING AND PERSISTENT ONSHORE FLOW WILL CONTINUE THROUGH
WEDNESDAY. THE WEATHER WILL BE ON THE DULL SIDE WITH NIGHT THROUGH
MORNING LOW CLOUDS AND FOG. SLOWER THAN NORMAL CLEARING LEADING TO
SUNNY AFTERNOON.

MAX TEMPS DROPPED 3 TO 6 DEGREES ON SATURDAY AND THE DEEPER MARINE
LAYER AND FALLING HGTS WILL ALLOW FOR ANOTHER 3 TO 6 DEGREE DROP
TODAY. MAX TEMPS WILL THEN BE FAIRLY STEADY AND 4 TO 6 DEGREES BLO
NORMAL.

.LONG TERM (THU-SAT)...
INTERESTING TIMES IN THE XTND FORECAST. BOTH THE EC AND THE GFS
DRIVE A COOL (FOR THIS TIME OF YEAR) UPPER LOW OUT OREGON AND DOWN
INTO CALIFORNIA. THE GFS BRINGS THE CENTER OF THE LOW AS FAR SOUTH
AS FRESNO WHILE THE EC BRINGS IT ALL THE WAY TO LA COUNTY. THURSDAY
WILL BE DRY BUT THERE WILL BE PLENTY OF MORNING STRATUS COVERING
EVERYTHING UP TO THE CSTL SLOPES SKIES WILL THEN TURN PARTLY CLOUDY
AS MID AND HIGH LEVEL CLOUDS ARRIVE ON THE LEADING EDGE OF THE LOW.
THE MAIN INSTABILITY AND THE LIFT OF THE UPPER LOW WILL ARRIVE ON
FRIDAY. SINCE THE LOW HAS NO OVER OCEAN TRAJECTORY IT WILL BE ON THE
DRY SIDE AND RIGHT NOW IT IS ONLY DESERVING OF ONLY A SLIGHT CHC OF
RAIN. ITS TOO EARLY TO TEASE OUT CONVECTIVE PARAMETERS BUT ITS NOT
HARD TO IMAGINE CONDITIONS CONDUCIVE TO TSTM FORMATION. THE SLGT CHC
WILL PERSIST THROUGH FRIDAY EVENING AND THEN FADE AS THE UPPER LOW
PUSHES EAST.

THE CLOUDS AND THE ABNORMALLY LOW HGTS WILL MAKE FOR A COUPLE OF
CHILLY DAYS WITH MAX TEMPS 8 TO 12 DEGREES BLO NORMAL AND MOSTLY IN
THE 60S.

RIDGING ARRIVES FOR THE WEEKEND AND THE MAX TEMPS WILL JUMP UP.
THERE WILL LIKELY NOT BE ANY MARINE LAYER CLOUDS AS THE MARINE
INVERSION WILL BE PRETTY WELL MIXED OUT AND IT WILL DAY A COUPLE OF
DAYS TO REFORM.

&&

.AVIATION...

03/1150Z

MARINE LAYER AT LAX AT 1145Z WAS 2100 FEET DEEP AND THE INVERSION
TOP WAS AT 3500 FEET WITH A TEMP OF 18 DEGREES C.

GOOD CONFIDENCE THAT LOW CLOUDS WILL COVER ALL COASTAL AND VLY TAF
SITES BY DAWN. MODERATE CONFIDENCE THAT MVFR CIGS WILL LINGER PAST
20Z ALONG THE COAST AND PAST 17Z FOR VALLEYS. SLOWER THAN NORMAL
CLEARING WITH EARLY AFTERNOON CLEARING LIKELY FOR COASTAL SITES AND
A 30 PERCENT CHC OF NO CLEARING AT ALL.

KLAX...GOOD CONFIDENCE THAT MVFR CIGS WILL LINGER THROUGH
21Z...THERE IS A 30 PERCENT CHC OF NO CLEARING AT ALL SUNDAY
AFTERNOON.

KBUR...GOOD CONFIDENCE THAT LOW MVFR CIGS WILL COVER THE TERMINAL
BUT LOWER CONFIDENCE IN EXACT TIMING STRATUS WILL SCOUR OUT. 20
PERCENT CHANCE THAT CIGS WILL LINGER PAST 19Z.

&&

.MARINE...

03/215 AM.

SMALL CRAFT ADVISORY FOR WINDS ARE NOT EXPECTED THROUGH MONDAY.
NORTHWEST WINDS ARE EXPECTED TO INCREASE TUESDAY AND THERE IS A
POTENTIAL OF SMALL CRAFT ADVISORY CONDITIONS MAINLY NORTH OF SAN
MIGUEL ISLAND TUESDAY AFTERNOON THROUGH EARLY FRIDAY. OTHERWISE A
LONG PERIOD SWELL FROM ABOUT 190 DEGREES WILL ARRIVE THIS MORNING
AND PEAK BY MONDAY. THE SWELL WILL REMAIN BELOW SMALL CRAFT ADVISORY
THRESHOLDS FOR HAZARDOUS SEAS.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY (SEE LAXCFWLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).

&&

$$

PUBLIC...GOMBERG/RORKE
AVIATION/MARINE...KAPLAN/RAT
SYNOPSIS...SWEET

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