481
FXUS66 KLOX 211546
AFDLOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
846 AM PDT MON SEP 21 2026
SYNOPSIS
21/240 AM.
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-WED)
21/826 AM.
***UPDATE***
ELEVATED BUT SHALLOW CONVECTION WAS MORE ACTIVE THAN MODELED OVER
INTERIOR SAN LUIS OBISPO AND NORTHERN SANTA BARBARA COUNTIES EARLY
THIS MORNING. NO LIGHTNING WAS OBSERVED, AND ANY RAIN THAT MADE IT
THROUGH THE DRY LAYER BELOW THIS ACTIVITY WAS PROBABLY LIGHT. THE
ACTIVITY WAS WANING AROUND 8 AM AND ANY LINGERING ISOLATED LIGHT
SHOWERS OR DRIZZLE SHOULD END IN THOSE AREAS BY MID TO LATE
MORNING AS MID- LEVEL DRYING TRENDS TAKE HOLD IN THE WAKE OF THE
SLOW MOVING UPPER LOW. ELSEWHERE, LIGHT DRIZZLE WAS COMMON
OVERNIGHT INTO EARLY THIS MORNING AND MAY CONTINUE AT TIMES WHERE
LOW CLOUDS PERSIST.
THE POSITION OF THE LOW WILL PASS NEAR THE NORTHERN VENTURA
MOUNTAINS BY EARLY AFTERNOON AND COINCIDE WITH SOME POOLING OF LOW
LEVEL MOISTURE. THIS COMBINED WITH GOOD MID-LEVEL LAPSE RATES ON
THE ORDER OF 7+ DEG C/KM AND NEAR 500 CAPE WILL SUPPORT A SLIGHT
(5-15 PERCENT) CHANCE OF A THUNDERSTORM WITH CLOUD-TO-GROUND
LIGHTNING AND BRIEF GUSTY WINDS THE MAIN CONCERN.
***FROM PREVIOUS DISCUSSION***
A HIGH HGT (576 DAM) WILL MOVE OVER SRN CA TODAY. THE LIFT FROM
THIS LOW WILL DEEPEN THE MARINE TO ABOUT 4000 FT AND MARINE LAYER
STRATUS WILL COVER ALL OF THE CSTS AND VLYS. SOME DRIZZLE IS
POSSIBLE THIS MORNING ESP NEAR THE FOOTHILLS. LOOK FOR SLOW
CLEARING AND A GOOD CHANCE OF REVERSE CLEARING WHERE THE CSTS
CLEAR FASTER THAN THE VLYS. THE DEEP MARINE LAYER, FALLING HGTS
AND STUBBORN WIDESPREAD CLOUDS WILL BRING 4 TO 8 DEGREES OF
COOLING TO ALL AREAS. HIGHS TODAY ACROSS THE CSTS AND VLYS WILL
MOSTLY BE IN THE 70S WITH A SMATTERING OF LOWER 80S. MOST MAX
TEMPS WILL END UP AROUND 8 DEGREES UNDER NORMAL.
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.
LONG TERM (THU-SUN)
21/241 AM.
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.
AVIATION
21/0940Z.
AT 0832Z AT KLAX, THE MARINE LAYER WAS 1900 FT DEEP. THE TOP OF
THE INVERSION WAS AT 4900 FT WITH A TEMPERATURE OF 19 C.
HIGH CONFIDENCE IN VFR CONDS FOR KPMD & KWJF.
LOW TO MODERATE CONFIDENCE IN THE REMAINING SITES. THE TIMING OF
CIG AND ANY VSBY RESTRICTIONS MAY BE OFF 2 HRS AND FLIGHT MINIMUMS
BY ONE CATEGORY. CIGS MAY BOUNCE BETWEEN CATEGORIES. THERE IS A
10 PERCENT CHANCE OF -DZ THROUGH 18Z.
KLAX...MODERATE CONFIDENCE IN TAF. CIGS MAY VARY BETWEEN 015 AND
030 THROUGH 18Z. THERE IS A 30 PERCENT CHC OF NO CLEARING. ANY
EAST WIND COMPONENT IS EXPECTED REMAIN LESS THAN 6KT.
KBUR...MODERATE CONFIDENCE IN TAF. THERE IS A 30 PERCENT CHC OF
BKN015 CONDS THROUGH 14Z.
MARINE
21/845 AM.
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 THIS AFTERNOON 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, 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 FROM 3 PM THIS AFTERNOON TO 9
PM PDT THIS EVENING FOR ZONE 650. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT FROM 3 PM THIS AFTERNOON TO 5
AM PDT TUESDAY FOR ZONES 673-676. (SEE LAXMWWLOX).
PUBLIC...RM/RORKE
AVIATION...RORKE
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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