175
FXUS66 KLOX 212107
AFDLOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
207 PM PDT MON SEP 21 2026
SYNOPSIS
21/204 PM.
A WEAK UPPER LEVEL TROUGH WILL MOVE OVER THE AREA TODAY, COOLING
TEMPERATURES AND INCREASING MARINE LAYER STRATUS. A WARMING TREND
WILL BEGIN TUESDAY AND PEAK ON WEDNESDAY, WITH HIGHS 5 TO 10
DEGREES ABOVE NORMAL.
SHORT TERM (TDY-THU)
21/204 PM.
THE POSITION OF A UPPER LOW WAS NEAR OVERHEAD TODAY, SUPPORTING A
DEEP MARINE LAYER WITH POCKETS OF SLOW TO BURN OFF LOW TO MID
LEVEL CLOUDS AND TEMPERATURES GENERALLY IN THE 70S. AN ISOLATED
AFTERNOON CUMULUS CLOUD HAS FORMED OVER THE VENTURA COUNTY
MOUNTAINS AND THERE IS STILL A 5-15 PERCENT CHANCE OF A SHOWER OR
THUNDERSTORM THROUGH 5 PM.
A SMALL RIDGE WILL MOVE INTO THE AREA TUESDAY AND WEDNESDAY. HGTS
WILL RISE TO ABOUT 582 DAM. MORE IMPORTANTLY THERE WILL BE GOOD
OFFSHORE TRENDS BOTH DAYS. THIS WILL LEAD TO ONLY WEAK ONSHORE
FLOW TO THE EAST AND ACTUAL OFFSHORE FLOW FROM THE NORTH IN THE
MORNINGS. LOOK FOR A REDUCTION IN THE MARINE LAYER CLOUD COVERAGE
AS WELL AS MUCH EARLIER AND COMPLETE CLEARING. MAX TEMPS WILL RISE
2 TO 4 LOCALLY 6 DEGREES ON TUESDAY. DUE THE WEAKENED ONSHORE
FLOW, WEDNESDAY WILL SEE A BIG 8 TO 12 DEGREE JUMP IN TEMPS.
WEDNESDAY'S TEMPS SHOULD MOSTLY END UP IN THE 80S ACROSS THE CSTS
AND IN THE 90S IN THE VLYS. THESE MAX TEMPS ARE 3 TO 6 DEGREES
ABOVE NORMAL EXCEPT FOR THE CENTRAL COAST WHERE THERE WILL BE
ABOUT 10 DEGREES OVER NORMAL. THERE IS A 20 TO 25 PERCENT CHC THAT
THE FORECAST IS NOT WARM ENOUGH AND MAX TEMPS WILL END UP HIGH
ENOUGH TO WARRANT SOME HEAT ADVISORIES. POCKETS OF BREEZY OFFSHORE
WINDS OF 20 TO 30 MPH ARE ANTICIPATED ACROSS INTERIOR MOUNTAINS
AND FOOTHILLS.
A REVERSAL TO ONSHORE FLOW WILL DRIVE A MODEST COOL DOWN INTO
THURSDAY, ALTHOUGH ABOVE NORMAL TEMPERATURES MAY CONTINUE FOR ONE
MORE DAY.
LONG TERM (FRI-MON)
21/203 PM.
BROAD TROFFING WILL LIKELY COVER THE STATE LATER THIS WEEK AND
INTO THE WEEKEND. THE GFS DOES FAVOR A RIDGE ON SUNDAY BUT THE EC,
THE EC-AI AND MANY ENSEMBLES SHOW THE TROF HANGING ON TO THE
COAST.
THE ONSHORE GRADIENTS WILL BE FAIRLY WEEK THROUGH THE PERIOD AND
THERE WILL BE SOME WEAK OFFSHORE FLOW FROM THE NORTH DURING THE
MORNINGS. THIS AND THE FACT THE TROFFING IS NOT VERY SHARP OR
DYNAMIC WILL LIKELY RESULT IN ONLY A PATCHY MARINE LAYER STRATUS
PATTERN.
MAX TEMPS WILL COOL A LITTLE ON MOST OF THE DAYS, BUT MOST TEMPS
WILL REMAIN A FEW DEGREES ABOVE NORMAL. BLENDED ENSEMBLE GUIDANCE
SHOWS 4 TO 8 DEGREES OF COOLING ON SUNDAY, BUT THIS MAY BE OVER
DONE GIVEN THE 586 FCST HGTS AND OFFSHORE FLOW FROM THE NORTH IN
THE MORNING.
DISTANT TROPICAL CYCLONES MAY SEND ANOTHER ROUND OF SWELLS AND
LARGE SURF AND DANGEROUS RIP CURRENTS TO SOUTH OR SOUTHWEST
FACING COASTS BY LATE THIS WEEKEND. WE COULD SEE SOME INCREASING
MID TO HIGH CLOUDS WELL AHEAD OF THESE SYSTEMS.
AVIATION
21/1732Z.
AT 1659Z AT KLAX, THE MARINE LAYER WAS 4400 FT DEEP. THE TOP OF
THE INVERSION WAS AT 6800 FT WITH A TEMPERATURE OF 14 C.
HIGH CONFIDENCE IN VFR CONDS FOR KPMD & KWJF.
LOW TO MODERATE CONFIDENCE IN THE REMAINING SITES. THERE IS A 40%
CHANCE FOR NO CLEARING TODAY AT KSBP/KSMX, WITH A 10% CHANCE AT LA
COUNTY SITES UNTIL AFTER 00Z. ARRIVAL OF CIGS TONIGHT MAY BE OFF
BY 3 HOURS, AND CONFIDENCE IS LOW IN MIN CIG HEIGHTS, WHERE TAFS
MAY BE OFF MY ONE CATEGORY. THERE IS A CHANCE FOR NO CIGS TONIGHT
AT KOXR/KCMA (40%), KBUR/KVNY (30%), KLAX/KLGB/KSMO (20%). THERE
IS A 20% CHANCE FOR BRIEF IFR-MVFR CIGS AT KSBA AFTER 12Z.
KLAX...MODERATE CONFIDENCE IN TAF. BKN040+ CIGS MAY LINGER THROUGH
22Z, WITH A 10% CHANCE FOR NO CLEARING UNTIL AFTER 00Z. LOW
CONFIDENCE IN RETURN TIMING (+/- 3 HOURS) AND MIN CIG HEIGHT
(015-025). THERE IS A 20% CHANCE FOR NO LOW CLOUDS TONIGHT. ANY
EAST WIND COMPONENT IS EXPECTED REMAIN LESS THAN 6KT.
KBUR...MODERATE CONFIDENCE IN TAF. BKN035+ CIGS MAY LINGER
THROUGH 22Z, WITH A 10% CHANCE FOR NO CLEARING UNTIL AFTER 00Z.
LOW CONFIDENCE IN RETURN TIMING (+/- 3 HOURS) AND MIN CIG HEIGHT
(008-015). THERE IS A 30% CHANCE FOR NO LOW CLOUDS TONIGHT.
MARINE
21/207 PM.
GOOD CONFIDENCE IN SMALL CRAFT ADVISORY (SCA) WEST TO NORTHWEST
WINDS ACROSS THE OUTER WATERS SOUTH AND WEST OF POINT SAL AND
THROUGH THE SANTA BARBARA CHANNEL CONTINUING THROUGH TONIGHT. SCA
WINDS ARE EXPECTED TO BECOME MORE WIDESPREAD TOMORROW AFTERNOON
INTO EARLY WEDNESDAY, INCLUDING ACROSS THE NEARSHORE CENTRAL COAST
WATERS. WINDS ARE EXPECTED TO DECREASE SOME WEDNESDAY WITH ONLY A
30-50% CHANCE FOR SCAS (HIGHEST ACROSS THE NORTHERN-MOST OUTER
WATERS), THEN SCA NORTHWEST WINDS WILL LIKELY RETURN ACROSS THE
OUTER WATERS, NEARSHORE CENTRAL COAST WATERS, AND POTENTIALLY THE
SANTA BARBARA CHANNEL AS EARLY AS LATE THURSDAY INTO THE WEEKEND.
LOX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 9 PM PDT THIS EVENING
FOR ZONE 650. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT UNTIL 5 AM PDT TUESDAY FOR
ZONES 673-676. (SEE LAXMWWLOX).
PUBLIC...RM/RORKE
AVIATION...LEWIS
MARINE...LEWIS
SYNOPSIS...MW/SIRARD
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
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