408
FXUS66 KLOX 201624
AFDLOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
824 AM PST SAT DEC 20 2025
SYNOPSIS
19/452 PM.
MOSTLY CLEAR SKIES ARE EXPECTED THROUGH SATURDAY EXCEPT FOR
OVERNIGHT TO MORNING LOW CLOUDS AND FOG NEAR THE COAST. IT WILL
BE COOLER EACH DAY, BUT HIGH TEMPERATURES WILL REMAIN ABOVE
NORMAL. THERE WILL BE INCREASING CLOUDS, COOLER TEMPERATURES AND
A SLIGHT CHANCE OF RAIN OVER SAN LUIS OBISPO COUNTY SUNDAY AND
MONDAY. A STRONG STORM WILL BRING MANY INCHES OF RAIN TO THE
ENTIRE AREA TUESDAY THROUGH WEDNESDAY.
SHORT TERM (TDY-MON)
20/823 AM.
***UPDATE***
LATEST SATELLITE AND SURFACE OBSERVATIONS INDICATE SOME STRATUS
AND FOG ACROSS THE COASTS AND VALLEYS WITH SOME HIGH CLOUDS
DRIFTING OVERHEAD. CURRENT SOUNDING DATA INDICATES MARINE
INVERSION IN THE 1000-1500 FOOT RANGE.
FORECAST-WISE FOR THE IMMEDIATE SHORT TERM, NO SIGNIFICANT ISSUES
ARE EXPECTED. CURRENT STRATUS AND PATCHY DENSE FOG WILL DISSIPATE
BY LATE THIS MORNING WITH HIGH CLOUDS PROVIDING A PARTLY CLOUDY TO
MOSTLY SUNNY AFTERNOON (WITH THE CLOUDIEST CONDITIONS ACROSS SAN
LUIS OBISPO COUNTY). BY LATE THIS AFTERNOON AND EVENING, THERE IS
A SLIGHT CHANCE OF SOME RAIN DEVELOPING ACROSS NORTHWEST SAN LUIS
OBISPO COUNTY, BUT NOTHING THAT WILL BE PROBLEMATIC. AS FOR
TEMPERATURES, WILL EXPECT SOME COOLING TODAY ACROSS VENTURA AND LA
COUNTIES WITH RETURN OF ONSHORE GRADIENTS. HOWEVER ACROSS SAN
LUIS OBISPO AND SANTA BARBARA COUNTIES, THERE MAY BE SOME SLIGHT
WARMING TODAY IN MOST AREAS.
OVERALL, CURRENT FORECAST HAS GOOD HANDLE ON THE IMMEDIATE SHORT
TERM. SO, NO SIGNIFICANT UPDATES ARE EXPECTED. FOR THE AFTERNOON
FORECAST SUITE, ATTENTION WILL BE RIVETED UPON CHRISTMAS EVE AND
CHRISTMAS DAY STORM. QUICK LOOK AT SOME PRELIMINARY 12Z DATA DOES
NOT INDICATE ANY SIGNIFICANT CHANGES FROM PREVIOUS THINKING, BUT
TIME WILL TELL.
***FROM PREVIOUS DISCUSSION***
IT'S STILL VERY MUCH THE CALM BEFORE THE STORM ACROSS SOUTHERN
CALIFORNIA AS MANY AREAS YESTERDAY ENJOYED TEMPERATURES WELL INTO
THE 70S AND EVEN A SPRINKLING OF 80S, ESPECIALLY SOUTH OF PT
CONCEPTION. IT WASN'T QUITE AS WARM ALONG THE CENTRAL COAST BUT
STILL AT LEAST A FEW DEGREES ABOVE NORMAL.
IT WON'T BE QUITE AS WARM TODAY ACROSS COAST AND VALLEYS OF
LA/VENTURA COUNTIES AS LIGHT OFFSHORE FLOW HAS TURNED STRONGLY
ONSHORE THIS MORNING AND A DEEPENING MARINE LAYER HAS RAPIDLY
PUSHED INLAND INTO THE LOWER VALLEYS. WHILE MOST OF THAT WILL
CLEAR BY AFTERNOON, TEMPERATURES WILL TAKE A HIT BY AT LEAST A FEW
DEGREES, ESPECIALLY IN THE VALLEYS. THIS MINOR COOLING TREND WILL
CONTINUE INTO SUNDAY AS WELL BUT EVEN WITH THAT HIGHS WILL STILL
BE ABOUT 5-10 DEGREES ABOVE NORMAL.
MEANWHILE, ACROSS THE ANTELOPE VALLEY TEMPERATURES WILL FEEL
DOWNRIGHT BALMY THIS WEEKEND WITH HIGHS IN THE MID TO UPPER 70S
BOTH DAYS AND AGAIN A STRONG CHANCE OF BREAKING DAILY TEMPERATURE
RECORDS.
ALONG THE CENTRAL COAST TEMPERATURES WILL ALSO REMAIN ROUGHLY 5
DEGREES ABOVE NORMAL TODAY BUT THERE WILL BE SOME INCREASING HIGH
CLOUDS AND COOLER TEMPERATURES THIS WEEKEND, ESPECIALLY BY
SUNDAY, AS THE ATMOSPHERIC RIVER OVER NORTHERN CALIFORNIA STARTS
TO SAG SOUTH. THE WESTERN PORTION OF SLO COUNTY COULD EVEN SEE
SOME LIGHT SHOWERS DEVELOPING AS EARLY AS SUNDAY OR MONDAY WITH
MAYBE A SPRINKLE AS FAR SOUTH AS SANTA MARIA.
THAT'S ABOUT AS FAR SOUTH AS ANY RAIN WILL REACH THROUGH AT LEAST
MONDAY WITH TOTAL AMOUNTS GENERALLY LESS THAN A QUARTER INCH.
FARTHER SOUTH, CLOUDS WILL BE INCREASING SOUTH OF PT CONCEPTION
BUT TEMPERATURES WILL REMAIN 5-10 DEGREES ABOVE NORMAL MONDAY AWAY
FROM THE IMMEDIATE COAST. MUCH COOLER AT THE COAST THOUGH WITH
LINGERING MARINE LAYER STRATUS POSSIBLY WELL INTO THE AFTERNOON.
LONG TERM (TUE-FRI)
20/409 AM.
A SIGNIFICANT AR STORM IS EXPECTED TO MOVE THROUGH THE AREA NEXT
WEEK. WHILE THERE IS STILL SOME UNCERTAINTY IN THE TOTAL RAIN
AMOUNTS, CONFIDENCE IS HIGH THAT MOST LOWER ELEVATION AREAS WILL
SEE AT LEAST 3-5 INCHES OF RAIN WHILE MOUNTAINS RECEIVE AT LEAST
5-10 INCHES WITH SNOW MOSTLY ABOVE 7000 FEET. AS IT LOOKS NOW,
LIGHT RAIN WILL SPREAD SOUTH OF PT CONCEPTION TUESDAY AFTERNOON
AND EVENING THEN TURN MUCH HEAVIER LATER TUESDAY NIGHT INTO
WEDNESDAY. SPECIFIC HOURLY AMOUNTS AND TIMING WILL BECOME A LITTLE
CLEARER ONCE WE GET INTO THE WINDOW OF THE HIGHER RES MODELS
LATER SUNDAY INTO MONDAY, BUT EVEN NOW THE LOWER RES MODELS ARE
INDICATING A 60-70% CHANCE OF ONE INCH PER HOUR RAIN RATES ACROSS
THE TRANSVERSE RANGE FROM SANTA BARBARA TO VENTURA COUNTIES, WITH
ABOUT AT LEAST A 50% CHANCE OF 0.75" PER HOUR ANYWHERE SOUTH OF PT
CONCEPTION. THE TARGET TIME FOR THE HEAVIEST RAIN IS CURRENTLY
TUESDAY NIGHT INTO WEDNESDAY AFTERNOON. COULD ALSO SEE SOME
ISOLATED THUNDERSTORMS DURING THIS TIME AS WELL. FOR RESIDENTS IN
UNSTABLE AREAS AND AREAS PRONE TO FLOODING AND MUDSLIDES THIS
WOULD BE A GOOD TIME TO TAKE THE NECESSARY PRECAUTIONS.
CHRISTMAS DAY LOOKS WET AS WELL, BUT LIKELY LIGHTER OVERALL THAN
WEDNESDAY. BASED ON THE LATEST MODELS, AT LEAST 70% OF THE RAIN
FROM THIS SYSTEM SHOULD FALL BEFORE CHRISTMAS DAY.
SHOWERS ARE EXPECTED TO CONTINUE OFF AND ON THROUGH AT LEAST
FRIDAY AFTERNOON AS THE TROUGH REMAINS WEST OF PT CONCEPTION AND
A FAVORABLE SOUTH TO SOUTHWEST FLOW ALOFT WILL KEEP GENERATING
LIGHT SHOWERS ACROSS THE AREA, PARTICULARLY IN UPSLOPE AREAS.
BECAUSE THIS SOURCE REGION OF THIS STORM WAS OVER A LOWER LATITUDE
SNOW LEVELS WILL BE QUITE HIGH FOR MOST OF THE EVENT, GENERALLY
AT OR WELL ABOVE 7000 FEET.
AVIATION
20/1015Z.
AROUND 09Z, THE MARINE LAYER DEPTH WAS NEAR 1600 FEET DEEP AT KLAX.
THE TOP OF THE MARINE INVERSION WAS AROUND 2100 FEET WITH A
TEMPERATURE NEAR 16 DEGREES CELSIUS. THERE WAS ANOTHER INVERSION
ABOVE UP TO AROUND 4300 FEET.
HIGH CONFIDENCE IN THE CURRENT FORECAST FOR DESERT TERMINALS.
LOW TO MODERATE CONFIDENCE EXISTS IN THE COASTAL AND VALLEY
TERMINALS. PRIMARILY LIFR TO IFR CONDITIONS ARE EXPECTED THROUGH
16Z AT LOS ANGELES COUNTY COASTAL TERMINALS AND VLIFR TO LIFR
CONDITIONS AT ALL REMAINING COASTAL AND VALLEY TERMINALS, THEN
CONDITIONS SHOULD IMPROVE ONE CATEGORY. VFR CONDITIONS SHOULD
DEVELOP BETWEEN 16Z AND 19Z, BUT THERE IS LOW TO MODERATE CHANCE
OF MVFR CONDITIONS REMAINING IN PLACE THROUGH THE AFTERNOON.
AN EARLY RETURN OF IFR TO MVFR CONDITIONS SHOULD BE EXPECTED FOR
THE COASTAL TERMINALS, THEN MOVING INTO VALLEY TERMINALS
OVERNIGHT AND LOWERING.
KLAX...LIFR TO IFR CONDITIONS ARE EXPECTED THROUGH AT LEAST
16Z, THEN CONDITIONS SHOULD IMPROVE TO THE IFR TO MVFR
CONDITIONS. VFR CONDITIONS SHOULD DEVELOP AROUND 20Z, BUT THERE IS
A 30 PERCENT CHANCE OF MVFR CONDITIONS REMAINING IN PLACE THROUGH
THE AFTERNOON. A RETURN OF IFR TO MVFR CONDITIONS COULD OCCUR AS
SOON AS 23Z OR AS LATE AS 03Z.
KBUR...VLIFR TO LIFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 16Z,
THEN CONDITIONS SHOULD IMPROVE ONE CATEGORY. VFR CONDITIONS
SHOULD DEVELOP BETWEEN 18Z AND 19Z, BUT THERE IS A 10 PERCENT
CHANCE OF MVFR VISIBILITIES THROUGH AS LATE AS 22Z. IFR
CONDITIONS SHOULD RETURN AS SOON AS 04Z, OR AS LATE AS 10Z.
MARINE
20/815 AM.
HIGH CONFIDENCE IN THE CURRENT FORECAST THROUGH MONDAY NIGHT,
THEN MODERATE CONFIDENCE THEREAFTER. CONFIDENCE LOWER DUE TO
TIMING AND SEAS. WITH EXCEPTION OF SMALL CRAFT ADVISORY (SCA) WIND
GUSTS INTO THIS AFTERNOON S AND W OF THE CHANNEL ISLANDS, WINDS
AND SEAS WILL LARGELY REMAIN BELOW SCA LEVELS THROUGH MONDAY
NIGHT.
ON TUESDAY, WINDS AND SEAS WILL LIKELY RAPIDLY INCREASE TO
DANGEROUS LEVELS AS A STORM SYSTEM APPROACHES THE COASTAL WATERS.
THERE IS A 70-90 PERCENT CHANCE OF SCA LEVEL SOUTHERLY WINDS
DEVELOPING BY TUESDAY EVENING WITH A LIKELY (60-70 PERCENT) CHANCE
OF WIDESPREAD GALE FORCE WINDS. LARGE SHORT-PERIOD SEAS ARE LIKELY
TO DEVELOP BY WEDNESDAY AND THURSDAY. AFTER THE FRONTAL PASSAGE,
THERE IS A MODERATE CHANCE FOR SCA LEVEL WEST TO NORTHWEST WINDS
FRIDAY.
BOATERS ARE URGED TO MONITOR THE LATEST WEATHER FORECASTS. IF
MARINE WEATHER CONDITIONS DETERIORATE AS ADVERTISED, BOATERS
SHOULD REMAIN IN SAFE HARBOR DURING THIS SIGNIFICANT STORM.
UNPROTECTED SOUTH FACING HARBORS MAY BE ESPECIALLY VULNERABLE TO
THE SOUTH SWELL AND WINDS.
LOX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 3 PM PST THIS AFTERNOON
FOR ZONES 673-676. (SEE LAXMWWLOX).
PUBLIC...MW/THOMPSON
AVIATION...HALL
MARINE...HALL/SIRARD
SYNOPSIS...30/CILIBERTI
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
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