248
FXUS66 KLOX 221857
AFDLOX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1057 AM PST MON DEC 22 2025
SYNOPSIS
22/159 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-WED)
22/911 AM.
***UPDATE***
LATEST SATELLITE AND SURFACE OBSERVATIONS INDICATE PARTLY TO
MOSTLY CLOUDY SKIES ACROSS THE AREA. ADDITIONALLY, THERE IS SOME
PATCHY DENSE FOG ACROSS THE AREA.
FORECAST-WISE FOR THE IMMEDIATE SHORT TERM, NO SIGNIFICANT ISSUES
ARE EXPECTED. SKIES WILL REMAIN PARTLY TO MOSTLY CLOUDY THROUGH
THE DAY AS MID/HIGH LEVEL CLOUDS WILL CONTINUE TO STREAM ACROSS
THE AREA. THERE WILL CONTINUE TO BE A THREAT OF LIGHT RAIN ACROSS
NORTHWEST SAN LUIS OBISPO COUNTY THROUGH THE DAY.
OVERALL, CURRENT FORECAST HAS GOOD HANDLE ON THE IMMEDIATE SHORT
TERM. SO, NO SIGNIFICANT UPDATES ARE PLANNED. FOR THE AFTERNOON
FORECAST SUITE, ATTENTION WILL CONTINUE TO BE ON THE CHRISTMAS EVE
AND CHRISTMAS DAY STORM. VERY PRELIMINARY LOOK AT 12Z DATA DOES
NOT INDICATE ANY SIGNIFICANT CHANGES TO PREVIOUS FORECAST
THINKING.
***FROM PREVIOUS DISCUSSION***
***MAJOR STORM COMING WITH SIGNIFICANT HYDROLOGIC IMPACTS***
THE LATEST FORECAST HAS NO SIGNIFICANT DEVIATIONS FROM EARLIER
FORECASTS AS MOST OF THE ENSEMBLE MODELS CONTINUE TO ADVERTISE A
VERY STRONG SYSTEM TAPPING INTO SUBTROPICAL MOISTURE TO CREATE
COPIOUS AMOUNTS OF RAIN ACROSS MUCH OF THE AREA ALONG WITH VERY
STRONG WINDS AT TIMES.
IN THE MEANTIME, ANOTHER RELATIVELY QUIET WEATHER DAY MONDAY WITH
TEMPERATURES 5-15 DEGREES ABOVE NORMAL ACROSS VALLEYS AND INTERIOR
AREAS AND NEAR TO SLIGHTLY BELOW NORMAL AT THE COAST.
ON TUESDAY MOST AREAS WILL START OUT DRY THROUGH AT LEAST 10AM,
BUT WINDS WILL BE QUICKLY INCREASING AS THE TROUGH OFFSHORE
DEEPENS AND CAUSES SURFACE PRESSURES TO FALL RAPIDLY ACROSS
NORTHERN CALIFORNIA. MODELS ARE INDICATING A 15-18MB GRADIENT
BETWEEN LAX AND SFO BY TUESDAY EVENING. THE COASTAL WATERS OFF
THE CENTRAL COAST WILL NOTICE THIS FIRST WITH WINDS GUSTING UP TO
50KT ACROSS A WIDE AREA. WINDS WILL MOVE INLAND THROUGH THE DAY
ACROSS SLO AND SANTA BARBARA COUNTIES AS WELL AS ALL THE MOUNTAIN
AREAS THROUGH VENTURA AND LA COUNTIES WITH WIDESPREAD WINDS
BETWEEN 40 AND 60 MPH IN THOSE AREAS AND LOCAL GUSTS UP TO 80 MPH
IN SOME OF THE MORE FAVORED MOUNTAIN AREAS. TO THAT END, A HIGH
WIND WATCH HAS BEEN POSTED ACROSS THESE AREAS.
SINCE THIS SYSTEM IS APPROACHING FROM THE SOUTHWEST LIGHT SHOWERS
WILL BEGIN TO DEVELOP IN MANY AREAS AROUND THE SAME TIME, ROUGHLY
MID AFTERNOON TO EARLY EVENING. RAIN RATES AT LEAST THROUGH AROUND
MIDNIGHT WEDNESDAY WILL UNDER A TENTH OF AN INCH PER HOUR.
HOWEVER, MUCH HEAVIER RAIN IS EXPECTED WEDNESDAY AS A 60-70KT LOW
LEVEL JET AT A RIGHT ANGLE TO THE TRANSVERSE RANGE GENERATES A
HUGE UPSLOPE RAIN RATE ENHANCEMENT. THE STORM IS JUST STARTING TO
GET INTO THE RANGE OF THE HIGHER RES MODELS BUT BETWEEN MIDNIGHT
AND 4 AM WEDNESDAY THERE IS A 70-80% CHANCE OF 1 INCH PER HOUR
RAIN RATES IN THE MOUNTAINS BETWEEN SANTA BARBARA AND LA COUNTY
AND EVEN AROUND A 20% CHANCE OF RATES AS HIGH AS 1.5" PER HOUR.
OUTSIDE OF THE MOUNTAINS THERE IS SOME UNCERTAINTY WITH REGARD TO
INTENSITIES, PARTICULARLY VENTURA AND LA COUNTIES WHERE RAIN RATES
AT LEAST THROUGH WEDNESDAY MORNING ARE MOSTLY UNDER A THIRD OF AN
INCH PER HOUR. HOWEVER, GIVEN THE HIGH IVT VALUES AND A LONG
DURATION OF MOIST SOUTH FLOW IT SEEMS LIKELY THAT EVEN LOWER
ELEVATION AREAS WILL SEE EXTREMELY HIGH RAIN RATES AT TIMES ON
WEDNESDAY. WITH THIS IN MIND, RESIDENTS NEAR BURN AREAS AS WELL AS
AREAS THAT ARE PRONE TO MUDSLIDES NEED TO TAKE PROTECTIVE ACTIONS
NOW. WHILE THIS SYSTEM HAS NOT HAD A HISTORY OF WIDESPREAD
CONVECTIVE ACTIVITY, AND MODELS ARE NOT INDICATING MUCH LOCALLY,
AN ISOLATED THUNDERSTORM IS POSSIBLE AS WELL.
WINDS ARE EXPECTED TO DECREASE FROM WEST TO EAST ACROSS THE AREA,
STARTING ALONG THE CENTRAL COAST IN THE MORNING AND BY LATE
AFTERNOON AND EVENING ACROSS LA COUNTY.
LONG TERM (THU-SUN)
22/353 AM.
AFTER A LITTLE RESPITE IN THE RAIN RATES AND WINDS AFTER THE
FIRST IMPULSE MOVES THROUGH ON WEDNESDAY, A SECOND BURST OF RAIN
AND WIND IS EXPECTED ON CHRISTMAS DAY. INITIALLY IT WAS THOUGHT
THAT THE CHRISTMAS DAY RAIN WOULD BE FAIRLY BENIGN BUT MORE RECENT
MODELS ARE INDICATING A SIMILARLY STRONG LOW LEVEL JET OF 60-70KT
RETURNING THAT MORNING. IVT AND PW'S DO DROP OFF THURSDAY AND THE
LOWER RES MODELS ARE SHOWING A MARKED DECREASE IN RAIN RATES
(MOSTLY UNDER A HALF INCH PER HOUR), BUT GIVEN THE UPTICK IN THE
SOUTHERLY FLOW THERE IS A POSSIBILITY FOR AT LEAST SHORT BURST OF
MUCH HEAVIER RAIN. A SECOND BURST OF WIND IS EXPECTED AS WELL SO
THE PREVIOUSLY MENTIONED HIGH WIND WATCH WILL REMAIN IN EFFECT
THROUGH THURSDAY IN THE SAME AREAS.
THE TROUGH REMAINS WEST OF THE STATE THROUGH AT LEAST FRIDAY
AFTERNOON, THEN MOVES ONSHORE SATURDAY, MAINTAINING A CHANCE OF
SHOWERS THROUGH THE PERIOD, THOUGH GENERALLY MUCH LIGHTER WITH
INCREASING PERIODS OF NO RAIN. DRY WEATHER FINALLY EXPECTED BY
SUNDAY, ENDING WHAT COULD BE 5 CONSECUTIVE DAYS OF RAIN ACROSS
SOUTHERN CALIFORNIA.
IN SUMMARY...TUESDAY THROUGH SATURDAY LOOKS TO BE AN EXTENDED
PERIOD OF SIGNIFICANT RAINFALL. BY SATURDAY EVENING, RAINFALL
TOTALS WILL RANGE FROM 4-8 INCHES ACROSS COASTAL AND VALLEY AREAS
TO 8-12+ INCHES ACROSS THE FOOTHILLS AND MOUNTAINS. PLEASE TAKE
THE NECESSARY PROTECTIVE ACTIONS AS FLOODING AND DEBRIS FLOW WILL
BE A MAJOR ISSUE THIS UPCOMING WEEK.
AVIATION
22/1856Z.
AT 1813Z AT KLAX, THE MARINE LAYER WAS 800 FT DEEP. THE TOP OF
THE INVERSION WAS NEAR 2000 FEET WITH A TEMPERATURE OF 19 C.
HIGH CONFIDENCE IN VFR TAFS FOR DESERT AIRFIELDS (KPMD & KWJF).
LOW CONFIDENCE FOR REMAINING TAFS. TIMING OF CIG/VSBY RESTRICTIONS
COULD BE OFF BY +/- 3 HOURS, AND OFF BY UP TO 2 CATEGORIES AT ANY
POINT. -DZ COULD BE POSSIBLE WHERE CIGS ARE PRESENT.
RAPIDLY DETERIORATING CONDS LIKELY TUESDAY AFTERNOON TO EVENING
AS SIGNIFICANT WINTER STORM ENTERS THE REGION.
KLAX...LOW CONFIDENCE IN TAF. GOOD CONFIDENCE THAT ANY EAST WIND
COMPONENT REMAINS BELOW 7 KTS THROUGH 08Z. 20% CHC REACHING 7 KTS
THROUGH 12Z TUESDAY, THEN 40% 12Z-15Z TUESDAY, AND INCREASING TO
GREATER THAN 60% THEREAFTER THROUGH END OF FORECAST PERIOD.
RAPIDLY DETERIORATING CONDITIONS ARE LIKELY LATE TUESDAY AFTERNOON
OR EVENING WITH SOUTH CROSS WINDS POTENTIALLY GUSTING 15-25 KT,
MVFR/IFR CIGS/VSBYS WITH -RA/DZ AT TIMES.
KBUR...MODERATE CONFIDENCE IN TAF. GENERALLY EXPECTING VFR
CONDITIONS THROUGH 03Z TUE. LIFR TO IFR CIGS POSSIBLE FROM 06Z TO
12Z TUE THEN LIFTING TO IFR TO MVFR THEREAFTER.
MARINE
22/255 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 TONIGHT. PATCHY DENSE FOG WILL BE POSSIBLE THROUGH
TUESDAY MORNING.
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. SCA LEVEL SOUTHERLY WINDS WILL DEVELOP BY
TUESDAY AFTERNOON WITH A LIKELY (80-90 PERCENT) CHANCE OF
WIDESPREAD GALE FORCE WINDS THROUGH AT LEAST TUESDAY NIGHT WITH A
50-70 PERCENT CHANCE OF STORM FORCE WINDS 45-55 KT FOR THE WATERS
NORTH OF POINT SAL. 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.
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...HIGH WIND WATCH IN EFFECT FROM TUESDAY AFTERNOON THROUGH
THURSDAY AFTERNOON FOR ZONES 38-340>353-376>383. (SEE LAXNPWLOX).
FLOOD WATCH REMAINS IN EFFECT FROM TUESDAY AFTERNOON THROUGH
WEDNESDAY EVENING FOR ZONES
38-87-88-340>358-362-366>383-548. (SEE LAXFFALOX).
PZ...SMALL CRAFT ADVISORY IN EFFECT FROM 4 AM TO 1 PM PST TUESDAY
FOR ZONES 645-670-673. (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY IN EFFECT FROM 8 AM TO 1 PM PST TUESDAY
FOR ZONES 650-655-676. (SEE LAXMWWLOX).
GALE WATCH IN EFFECT FROM TUESDAY AFTERNOON THROUGH LATE
TUESDAY NIGHT FOR ZONES 650-655-676. (SEE LAXMWWLOX).
PUBLIC...MW/THOMPSON
AVIATION...BLACK/MUNROE
MARINE...RM/PHILLIPS/BLACK
SYNOPSIS...MW
WEATHER.GOV/LOSANGELES
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX
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