920
FXUS66 KLOX 210438
AFDLOX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
838 PM PST SAT DEC 20 2025
SYNOPSIS
20/649 PM.
MOSTLY CLEAR SKIES ARE EXPECTED THROUGH SUNDAY MORNING 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 ACROSS THE
ENTIRE AREA TUESDAY THROUGH AT LEAST FRIDAY.
SHORT TERM (SAT-TUE)
20/812 PM.
***UPDATE***
LOW CLOUDS AND FOG HAVE STARTED TO MAKE A RETURN TO THE COASTAL
WATERS TONIGHT, WHILE A THIN LAYER OF HIGHER LEVEL CLOUDS STREAM
OVERHEAD. THE LOW CLOUDS ARE EXPECTED TO EXPAND ACROSS ALL OF THE
COASTS OVERNIGHT, AND SLOW TO LITTLE CLEARING WILL BE POSSIBLE
LATE SUNDAY MORNING INTO AFTERNOON. SO FAR, ONLY A FEW STATIONS
HAVE DIPPED DOWN INTO THE DENSE FOG CRITERIA, BUT WITH HIGH CLOUDS
PRESENT NORTH OF POINT CONCEPTION, NOT EXPECTING THE DENSE FOG TO
LAST LONG.
NORTH OF POINT CONCEPTION, LIGHT RAIN WILL CONTINUE TO BE
POSSIBLE TONIGHT THROUGH MONDAY EVENING, BUT TOTALS WILL BE
LIGHT. HIGH TEMPS ON SUNDAY SHOULD BE SOMEWHAT SIMILAR TO THE
HIGHS TODAY, IN THE 60S AND 70S, SAVE FOR COOLING INTO THE LOWER
60S ACROSS AREAS NORTH OF POINT CONCEPTION DUE TO AN INCREASE IN
CLOUDS AND THREAT OF RAIN.
FORECAST LOOKS TO BE IN SHAPE AND NO UPDATES WERE NEEDED.
***FROM PREVIOUS DISCUSSION***
OVERALL, 12Z MODELS IN GOOD AGREEMENT THROUGH THE SHORT TERM
PERIOD. AT UPPER LEVELS, FLOW TURNS MORE SOUTHWESTERLY THROUGH
TUESDAY. NEAR THE SURFACE, WEAK ONSHORE FLOW WILL PREVAIL THROUGH
MONDAY THEN SOUTHEASTERLY FLOW WILL INCREASE DURING THE DAY ON
TUESDAY.
FORECAST-WISE, TODAY THROUGH MONDAY LOOKS TO BE RATHER UNEVENTFUL.
WITH LOWERING H5 HEIGHTS AND ONSHORE SURFACE FLOW, THERE WILL BE
AN INCREASE IN DEPTH/COVERAGE OF THE MARINE LAYER STRATUS.
ADDITIONALLY, MID/HIGH LEVEL CLOUDS WILL BE ON THE INCREASE ACROSS
THE AREA. GIVEN THE OVERALL FLOW PATTERN, THERE WILL BE A THREAT
OF RAIN ACROSS NORTHERN SAN LUIS OBISPO COUNTY BEGINNING THIS
EVENING AND CONTINUING THROUGH MONDAY. RAIN TOTALS THROUGH MONDAY
EVENING ACROSS SLO COUNTY WILL GENERALLY BE UNDER 0.10 INCHES
ALTHOUGH SANTA LUCIA MOUNTAINS COULD RECEIVE UP TO AROUND 0.50
INCHES.
ON TUESDAY, THE HOLIDAY "FUN" WILL BEGIN AS THE AR BEGINS TO SAG
SOUTHWARD ACROSS THE AREA. STEADY LIGHT RAIN WILL BEGIN ACROSS SLO
COUNTY TUESDAY MORNING AND WILL SPREAD SOUTH INTO LA COUNTY BY
TUESDAY AFTERNOON/EVENING. THROUGH THE AFTERNOON, RAINFALL
INTENSITIES WILL BE LIGHT, BUT THE RAIN INTENSITY WILL INCREASE TO
MODERATE LEVELS TUESDAY EVENING. THROUGH TUESDAY EVENING, RAIN
TOTALS WILL GENERALLY BE AROUND 0.25 INCHES OR LESS ALTHOUGH
SOUTH-FACING SLOPES OF SBA/VENTURA COUNTIES WOULD RECEIVE 0.50 TO
0.75 INCH TOTALS. SNOW LEVELS WILL REMAIN QUITE HIGH, ABOVE 7500
FEET, THROUGH TUESDAY EVENING. ALONG WITH THE INCREASING RAIN,
SOUTHEASTERLY WINDS WILL INCREASE DURING THE DAY ON TUESDAY.
WIDESPREAD ADVISORY-LEVEL WINDS ARE LIKELY FOR MOST AREAS WITH
EVEN A CHANCE OF WARNING-LEVEL GUSTS ACROSS THE MOUNTAINS
(ESPECIALLY THE SANTA LUCIA RANGE AND THE INTERSTATE 5 CORRIDOR).
LONG TERM (WED-SAT)
20/102 PM.
FOR THE EXTENDED, ALL MODELS INDICATE SYSTEMS ARE STILL A "GO" FOR
A VERY SIGNIFICANT WINTER STORM TO IMPACT THE AREA. ALL RESIDENTS
OF SOUTHWESTERN CALIFORNIA SHOULD BE PREPARED FOR A VERY STRONG
STORM.
ON CHRISTMAS EVE (WEDNESDAY), THE AR WILL EXERT ITS GREATEST PUNCH
TO THE AREA WITH MODERATE TO HEAVY RAINFALL FOR ALL AREAS. THIS
FIRST WAVE WILL MOVE ACROSS THE AREA WEDNESDAY MORNING AND
AFTERNOON WITH PRECIPITATION TAPERING OFF WEDNESDAY EVENING. ON
THURSDAY, A SECONDARY AR PUNCH WILL IMPACT THE AREA WITH
IMPRESSIVE RAINFALL AMOUNTS (BUT LESS THAN WHAT FALLS ON
WEDNESDAY). ON FRIDAY, ALL MODELS AGREE ON A CONTINUED SHOWER
THREAT ACROSS THE AREA. HOWEVER ON SATURDAY, MODELS DIVERGE WITH
THE GFS INDICATING ANOTHER SHOT OF MODERATE RAINFALL WHILE THE
ECMWF JUST INDICATES SCATTERED SHOWERS. HOWEVER, WILL NOT GET
BOGGED DOWN IN THOSE DIFFERENCES AT THE DAY 7-8 TIME FRAME.
THROUGH SATURDAY EVENING, RAINFALL TOTALS WILL BE VERY
IMPRESSIVE. NORTH OF POINT CONCEPTION, 2-4 INCHES IS EXPECTED FOR
COASTS/VALLEYS WITH 4-8 INCHES ACROSS THE FOOTHILLS AND MOUNTAINS.
SOUTH OF POINT CONCEPTION, AMOUNTS WILL EVEN BE MORE IMPRESSIVE,
4-6 INCHES FOR COASTAL/VALLEY AREAS AND 6-12+ INCHES FOR THE
FOOTHILLS AND MOUNTAINS. RAINFALL RATES ALSO WILL BE PRETTY
IMPRESSIVE. PEAK HOURLY RATES OF 0.50-1.00 INCHES ARE LIKELY SOUTH
OF POINT CONCEPTION AND 0.30-0.80 INCHES NORTH OF POINT
CONCEPTION. GIVEN THE AMOUNT OF EXPECTED RAINFALL AND THE
ASSOCIATED RATES, SIGNIFICANT HYDROLOGIC ISSUES CAN BE EXPECTED,
INCLUDING WIDESPREAD URBAN FLOODING AND THE THREAT OF MUD AND
DEBRIS FLOWS.
AS FOR SNOW, GIVEN THE NATURE OF THIS SYSTEM, SNOW LEVELS WILL
REMAIN RATHER HIGH THROUGH THE BULK OF THE PRECIPITATION. SNOW
LEVELS WILL REMAIN ABOVE THE 7000 FEET THROUGH CHRISTMAS DAY, BUT
WILL DROP INTO THE 5500-6500 FOOT RANGE FRIDAY THROUGH SATURDAY.
SO, RESORT LEVELS WILL LIKELY RECEIVE SOME IMPRESSIVE SNOW TOTALS
WHEN ALL IS SAID AND DONE, BUT LOWER ELEVATIONS WILL NOT.
AVIATION
21/0241Z.
AT 0039Z AT KLAX, THE MARINE LAYER WAS 1000 FEET DEEP. THE TOP OF
THE INVERSION WAS 4400 FEET WITH A TEMPERATURE NEAR 17 DEG C.
HIGH CONFIDENCE IN DESERT TAFS. LOW TO MODERATE CONFIDENCE FOR
THE 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 SUNDAY MORNING/AFTERNOON.
KLAX...LOW TO MODERATE CONFIDENCE IN TAF. THE TIMING OF FLIGHT
CAT CHANGES MAY BE OFF +/- 3 HOURS, AND OFF BY 1 CAT AT ANY POINT.
THERE IS A 30% CHANCE OF 1/4SM FG VV002 CONDS OVERNIGHT, BEFORE
IMPROVING AFTER 16Z. LITTLE TO NO CLEARING IS POSSIBLE SUNDAY
AFTERNOON. GOOD CONFIDENCE THAT ANY EAST WIND COMPONENT REMAINS
BELOW 6 KT.
KBUR...LOW TO MODERATE CONFIDENCE IN THE 18Z TAF. THERE IS A 50%
CHANCE VFR CONDS WILL DEVELOP AROUND 15Z SUN, BUT THERE IS ALSO A
50% CHANCE OF IFR CONDS THRU 18Z. THE TIMING OF FLIGHT CAT CHANGES
MAY BE OFF +/- 1 TO 2 HOURS.
MARINE
20/836 PM.
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 70-90 PERCENT CHANCE OF SCA LEVEL
SOUTHERLY WINDS DEVELOPING BY TUESDAY AFTERNOON WITH A LIKELY
(60-70 PERCENT) CHANCE OF WIDESPREAD GALE FORCE WINDS THROUGH
TUESDAY NIGHT. LARGE SHORT-PERIOD SEAS ARE LIKELY TO DEVELOP
TUESDAY NIGHT AND SHOULD LINGER WEDNESDAY INTO 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...NONE.
PZ...NONE.
PUBLIC...THOMPSON
AVIATION...LUND
MARINE...SIRARD/CILIBERTI
SYNOPSIS...CILIBERTI/KL
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