750
FXUS66 KLOX 211619
AFDLOX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
819 AM PST SUN DEC 21 2025
SYNOPSIS
21/238 AM.
TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH SUNDAY IN MOST
AREAS EXCEPT THE COAST. A COOLING TREND WILL BEGIN MONDAY AS A
STRONG STORM APPROACHES WITH INCREASING CLOUDS. RAIN WILL BEGIN
TUESDAY IN MOST AREAS WITH PERIODS OF HEAVY RAIN TUESDAY NIGHT AND
WEDNESDAY AS WELL AS VERY STRONG WINDS. SHOWERS ARE EXPECTED TO
CONTINUE ON CHRISTMAS DAY AND THROUGH NEXT WEEKEND.
SHORT TERM (TDY-TUE)
21/759 AM.
***UPDATE***
LATEST SATELLITE AND SURFACE OBSERVATIONS INDICATE WIDESPREAD
STRATUS AND FOG ACROSS THE COASTS/VALLEYS WITH HIGH CLOUDS
DRIFTING OVERHEAD. CURRENT SOUNDING DATA INDICATES MARINE
INVERSION IN THE 1000-1500 FOOT RANGE FOR DEPTH.
FORECAST-WISE FOR THE IMMEDIATE SHORT TERM, NO SIGNIFICANT ISSUES
ARE EXPECTED. AFTER STRATUS DISSIPATES THIS MORNING, PARTLY TO
MOSTLY CLOUDY SKIES WILL PREVAIL THROUGH THE AFTERNOON, THANKS TO
THE HIGH CLOUDS. ACROSS NORTHWEST SAN LUIS OBISPO COUNTY, LIGHT
RAIN WILL CONTINUE THROUGH THE DAY, BUT DRY CONDITIONS WILL
PREVAIL ELSEWHERE. COMPARED TO SATURDAY, HIGH TEMPERATURES TODAY
WILL BE VERY SIMILAR ALTHOUGH A COUPLE DEGREES COOLING IS LIKELY
ACROSS INTERIOR SECTIONS.
OVERALL, CURRENT FORECAST HAS GREAT HANDLE ON THE IMMEDIATE SHORT
TERM. SO, NO SIGNIFICANT UPDATES ARE EXPECTED. FOR THE AFTERNOON
FORECAST SUITE, ATTENTION WILL REMAIN ON THE MAJOR WINTER STORM
SET TO IMPACT THE AREA, BEGINNING ON TUESDAY AND CONTINUING
THROUGH THE WEEK.
***FROM PREVIOUS DISCUSSION***
***MAJOR STORM COMING WITH SIGNIFICANT HYDROLOGIC IMPACTS***
ENJOY THE ABOVE NORMAL TEMPERATURES AND DRY WEATHER BECAUSE
SOUTHERN CALIFORNIA IS IN FOR AT LEAST 5 CONSECUTIVE DAYS WITH AT
LEAST SOME RAIN EACH DAY. IN THE SHORT TERM, VERY LITTLE IMPACTFUL
WEATHER. AS MENTIONED, TEMPERATURES ARE ABOVE NORMAL, AND IN SOME
CASES 15-20 DEGREES ABOVE NORMAL. MINIMAL CHANGES IN THE WEATHER
ARE EXPECTED THROUGH MONDAY OTHER THAN A VERY SLIGHT COOLING TREND
FOR THE INTERIOR. THE ANTELOPE VALLEY HAS BEEN PARTICULARLY ABOVE
NORMAL WITH HIGHS IN THE MID TO UPPER 70S WHEN NORMAL IS IN THE
MID TO UPPER 50S. THERE MAY BE SOME LIGHT SHOWERS ALONG THE
NORTHWEST PORTION OF THE CENTRAL COAST BUT ANY AMOUNTS WOULD BE A
QUARTER INCH OR LESS.
ON TUESDAY THIS WILL ALL CHANGE. THE ATMOSPHERIC RIVER THAT HAS
BEEN POINTED TOWARDS NORTHERN CALIFORNIA THE LAST FEW DAYS WILL
SHIFT SOUTH AND TAKE AIM AT SOCAL. RAIN WILL MOVE SOUTH AROUND PT
CONCEPTION BY AFTERNOON BRINGING AT LEAST LIGHT RAIN TO MOST
AREAS BY EVENING IF NOT BEFORE. HEAVIER RAIN WILL DEVELOP TUESDAY
EVENING ALONG THE SOUTH FACING SLOPES OF THE SANTA BARBARA
MOUNTAINS, BOOSTED BY STRONG SOUTH TO SOUTHEAST WINDS AS HIGH AS
60 MPH THAT WILL DOUBLE OR EVEN TRIPLE THE RAIN RATES IN THOSE
AREAS. RAIN AMOUNTS WILL ALREADY BE CLOSE TO AN INCH IN THOSE
AREAS BEFORE MIDNIGHT. ELSEWHERE RAIN AMOUNTS THROUGH TUESDAY
EVENING WILL BE UNDER A HALF INCH. WILL LIKELY NEED A HIGH WIND
WATCH FOR SOME OR ALL OF THE CENTRAL COAST AND SOUTHERN SANTA
BARBARA COUNTY TUESDAY IN ADDITION TO FLOOD WATCHES.
LONG TERM (WED-SAT)
21/352 AM.
THE HEAVIEST AND MOST IMPACTFUL PART OF THIS AR STORM WILL OCCUR
AFTER MIDNIGHT TUESDAY NIGHT INTO WEDNESDAY WHEN IVT VALUES REACH
CLOSE TO 900 BASED ON THE EC ENSEMBLES AS THE STORM TAPS INTO DEEP
TROPICAL MOISTURE FROM THE SOUTH. IF THAT PANS OUT THAT COULD BE
HIGHEST IVT VALUE FROM A STORM IN THIS AREA IN QUITE SOME TIME, IF
NOT EVER. PW VALUES ARE EXPECTED TO REACH OR EXCEED 1.2" WHICH
WOULD VERY CLOSE TO THE HIGHEST PW MEASURED FOR THIS TIME OF
YEAR. HOURLY RAIN RATES, ESPECIALLY IN THE UPSLOPE AREAS, SHOULD
EASILY TOP ONE INCH PER HOUR DURING THE PEAK OF THE STORM ON
WEDNESDAY. THE HEAVIEST RAIN WILL BE IN THE SOUTH FACING
MOUNTAINS, BUT VERY HEAVY RAIN, POSSIBLY CLOSE TO AN INCH PER
HOUR, IS POSSIBLE AT LOWER ELEVATIONS AS WELL AND ANYONE IN
PARTICULARLY VULNERABLE AREAS SUCH AS THE SANTA YNEZ RANGE,
VENTURA MOUNTAINS, SANTA MONICA MOUNTAINS OR ANY RECENT BURN
SCARS SHOULD START TAKING PROTECTIVE ACTIONS ASAP. THERE WILL
ALMOST CERTAINLY BE NUMEROUS MUDSLIDES, SEVERE FLOODING EITHER
FROM HEAVY RAIN OR CLOGGED STORM DRAINS, AND POSSIBLY DEBRIS FLOWS
NEAR RECENT BURN SCARS. COULD EVEN SEE AN ISOLATED THUNDERSTORM OR
TWO, THOUGH THERE HASN'T BEEN MUCH OF THAT SO FAR WITH THIS STORM
OVER NORTHERN CALIFORNIA. HOWEVER, THE MOISTURE ADVECTION FROM THE
SOUTH COULD PROVIDE A BOOST IN INSTABILITY WEDNESDAY.
IN ADDITION TO THE RAIN, VERY STRONG WINDS UP TO 80MPH ARE
EXPECTED OVER THE HIGHER PEAKS IN THE MOUNTAINS, WITH GUSTS TO
40-50 MPH ACROSS LOWER ELEVATIONS.
WHILE THE WORST OF THE STORM WILL LIKELY BE WEDNESDAY, PERIODS OF
RAIN, POSSIBLY HEAVY AT TIMES, ARE EXPECTED ON CHRISTMAS DAY.
AND WITH THE TROUGH REMAINING OFFSHORE, MOIST SOUTH TO SOUTHWEST
FLOW WILL CONTINUE TO USHER IN OFF AND ON SHOWERS TO THE AREA
FRIDAY AND SATURDAY, THOUGH RAIN AMOUNTS BY THAT TIME SHOULD BE
UNDER A QUARTER INCH PER HOUR.
SNOW WILL NOT BE A MAJOR FACTOR WITH THIS EVENT. DURING THE PEAK
OF THE STORM SNOW LEVELS WILL BE AT OR ABOVE 9000 FEET. THEY WILL
COME DOWN THURSDAY AND FRIDAY TO AROUND 7000 FEET BUT THAT WILL
HAVE MINIMAL IMPACTS.
AVIATION
21/1217Z.
AT 10Z AT KLAX, THE MARINE LAYER WAS 1000 FEET DEEP. THE TOP OF
THE INVERSION WAS 3000 FEET WITH A TEMPERATURE NEAR 17 DEG C.
HIGH CONFIDENCE IN DESERT TAFS. LOW FOR REMAINDER OF TAFS. TIMING
OF FLIGHT CAT CHANGES COULD BE OFF BY +/- 3 HOURS, AND OFF BY 1
FLIGHT CAT AT ANY POINT. KPRB, KSBP, AND KSMX MAY SEE -DZ AT TIMES
THROUGH THE PERIOD.
LIFR TO VLIFR CONDS POSSIBLE AT ALL SITES, AND MAY BOUNCE FLIGHT
CATS AT TIMES. LITTLE TO NO CLEARING IS POSSIBLE FOR KPRB, KSMX,
KSBP, KSMO, AND KLAX.
KLAX...LOW CONFIDENCE IN TAF. THE TIMING OF FLIGHT CAT CHANGES
MAY BE OFF +/- 3 HOURS, AND OFF BY 1 CAT AT ANY POINT. LITTLE TO
NO CLEARING IS POSSIBLE. GOOD CONFIDENCE THAT ANY EAST WIND
COMPONENT REMAINS BELOW 6 KT.
KBUR...LOW CONFIDENCE IN TAF. THE TIMING OF FLIGHT CAT CHANGES
MAY BE OFF +/- 2 HOURS AND 1 CATEGORY.
MARINE
21/818 AM.
HIGH CONFIDENCE IN THE CURRENT FORECAST THROUGH MONDAY NIGHT,
THEN MODERATE CONFIDENCE THEREAFTER. CONFIDENCE LOWER DUE TO
TIMING AND SEAS. WINDS AND SEAS WILL LARGELY REMAIN BELOW SCA
LEVELS THROUGH MONDAY NIGHT.
ON TUESDAY, SE TO SOUTH WINDS AND SEAS WILL ARE EXPECTED TO
RAPIDLY INCREASE TO DANGEROUS LEVELS AS A STORM SYSTEM APPROACHES
THE COASTAL WATERS. THERE IS A 90+ PERCENT CHANCE OF SCA LEVEL
SOUTHERLY WINDS DEVELOPING BY TUESDAY AFTERNOON WITH A LIKELY
(80-90 PERCENT) CHANCE OF WIDESPREAD GALE FORCE WINDS THROUGH AT
LEAST TUESDAY NIGHT WITH A 20-40 PERCENT (HIGHEST NORTHERN WATERS)
CHANCE OF AT LEAST BRIEF STORM FORCE WINDS. LARGE SHORT- PERIOD
SEAS ARE LIKELY TO DEVELOP TUESDAY NIGHT AND SHOULD LINGER
WEDNESDAY INTO THURSDAY. THERE IS ALSO A 5-15% CHANCE OF
THUNDERSTORMS TUESDAY NIGHT THROUGH THURSDAY MORNING.
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...NONE.
PUBLIC...MW/THOMPSON
AVIATION...MUNROE/LUND
MARINE...RM/BLACK
SYNOPSIS...MW
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page