293
FXUS66 KSGX 190444
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
844 PM PST THU DEC 18 2025
SYNOPSIS
WARM AND DRY WEATHER WILL CONTINUE ACROSS THE REGION THROUGH THE
UPCOMING WEEKEND. NIGHT AND MORNING LOW CLOUDS AND FOG WILL
PERSIST ON FRIDAY, WITH LESS FOG FOR LOWER ELEVATIONS NEAR THE
COAST BY THE WEEKEND INTO EARLY NEXT WEEK. A LOW PRESSURE SYSTEM
WILL BRING LIGHT SHOWERS BEGINNING TUESDAY, EVOLVING INTO HEAVIER
RAINFALL ACROSS ALL AREAS BY WEDNESDAY. THE ACTIVE WEATHER PATTERN
LOOKS TO CONTINUE WITH ELEVATED RAIN CHANCES CONTINUING INTO THE
END OF NEXT WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
UPDATE: NIGHT FOG IMAGERY AT THIS HOUR REVEALS LOW CLOUDS CONTINUING
TO FORM ALONG MOST OF THE COASTAL AREAS OF SAN DIEGO COUNTY. THERE
COULD BE AREAS OF PATCHY FOG DEVELOPING THROUGHOUT THE NIGHT FOR
SOME OF THESE AREAS, AND ALREADY LOCATIONS AROUND THE OCEANSIDE AND
SOUTH BAY AREAS ARE ALREADY SEEING VISIBILITIES GOING DOWN TO A
QUARTER OF A MILE. THIS WILL CONTINUE TO BE MONITORED THROUGHOUT THE
NIGHT TO DETERMINE IF THERE IS GOING TO BE THE NEED FOR A DENSE FOG
ADVISORY. AS FAR AS THE FORECAST IS CONCERNED, MODELS ARE REMAINING
RATHER CONSISTENT IN STILL SHOWING THE RIDGE OVERHEAD BREAKING DOWN
GOING INTO THE WEEKEND AS A VERY BROAD AREA OF TROUGHING OVER THE E
PACIFIC WATERS CONTINUES TO SLOWLY ADVANCE TOWARDS THE REGION. IT
STILL APPEARS THAT THE TIMING OF THE FIRST PRECIP ASSOCIATED WITH
THIS IS LIKELY TO OCCUR ON TUESDAY OF NEXT WEEK (ALTHOUGH THERE
COULD BE SOME PATCHY AREAS OF DRIZZLE ON MONDAY AS WELL FOR SOME OF
THE INLAND AND COASTAL AREAS). THE MORE SIGNIFICANT RAINFALL IS NOT
GOING TO MOVE IN UNTIL WEDNESDAY (CHRISTMAS EVE) WITH THE CHANCE OF
RAIN CONTINUING THROUGH THURSDAY (CHRISTMAS DAY) BEFORE TAPERING
OFF THE FOLLOWING DAY. TOTAL STORM RAINFALL THROUGHOUT THE
DURATION OF THIS STORM MAY EXCEED 2.5 INCHES FOR ORANGE COUNTY,
OVER 2 INCHES WITHIN THE IE, AND THEN LESSER AMOUNTS TAPER FROM
NORTH TO SOUTH FOR THE LOWER ELEVATIONS. THE SAN BERNARDINO
MOUNTAINS MAY ALSO RECEIVE UP TO 4 INCHES POSSIBLY FOR SOME OF THE
SOUTH- SOUTHWEST FACING SLOPES. IT WILL BE A RELATIVELY WARM
STORM, AND THEREFORE SNOW LEVELS WILL REMAIN QUITE HIGH (OVER 7000
FT), ALTHOUGH SOME OF THE HIGHER ELEVATIONS, SUCH AS SAN GORGONIO
AND SAN JACINTO, MAY STILL PICK UP OVER A FOOT OF SNOW.
PREVIOUS DISCUSSION SUBMITTED AT 1057 AM:
HIGH TEMPERATURES FOR TODAY WILL BE MUCH WARMER FOR THE COAST AND
AND VALLEYS THAN YESTERDAY, WITH HIGHS 10 TO AS MUCH AS 25
DEGREES ABOVE NORMAL. HIGH TEMPERATURES FOR TODAY WILL RANGE FROM
AROUND 70 NEAR THE COAST TO THE UPPER 70S TO MID 80S FOR THE
VALLEYS AND FOR THE LOWER DESERTS. HIGH TEMPERATURE RECORDS FOR
TODAY ARE MOST LIKELY TO BE TIED OR BROKEN IN THE MOUNTAINS,
INLAND VALLEYS, AND LOWER DESERTS. SOME LOCATIONS THAT MAY BREAK
RECORDS INCLUDE CAMPO, ALPINE, BIG BEAR AND IDYLLWILD.
THE AREA OF HIGH PRESSURE WILL BEGIN TO BREAK DOWN AND FLATTEN
OVER MEXICO AS A TROUGH PUSHES SOUTHWARD FROM THE GULF OF ALASKA
INTO THE PACIFIC NORTHWEST BY EARLY NEXT WEEK. THIS WILL LEAD TO
GREATER ONSHORE FLOW AND A SUBTLE COOLING TREND BY THE WEEKEND
INTO MONDAY, THOUGH TEMPERATURES WILL STILL BE AROUND 5 TO 15
DEGREES ABOVE NORMAL. THIS WILL ALSO HELP THE MARINE LAYER DEEPEN,
LEADING TO FOGGY CONDITIONS TO REMAIN IN MORE ELEVATED TERRAIN
AWAY FROM THE COAST EACH MORNING.
A MOISTURE PLUME/ATMOSPHERIC RIVER ("PINEAPPLE EXPRESS")
CURRENTLY FROM HAWAII CONTINUES TO PUMP MOISTURE INTO THE PACIFIC
NORTHWEST. THIS SYSTEM, ALONG WITH THE AFOREMENTIONED TROUGH TO
THE NORTH, WILL COMBINE AND PUSH THIS ATMOSPHERIC RIVER SOUTHWARD
INTO OUR REGION BY TUESDAY THROUGH THE CHRISTMAS HOLIDAY. TIMING
STILL REMAINS FAIRLY UNCERTAIN ON WHEN THIS MAY OCCUR AS THE
TROUGH OF LOW PRESSURE MAY ELONGATE OVER THE OCEAN, DELAYING THE
RAIN'S ONSET. THE MOST LIKELY SCENARIO IS TO SEE SOME LIGHT
SHOWERS DEVELOPING OUT AHEAD OF THE STORM SYSTEM SOMETIME ON
TUESDAY. MODELS SUGGEST WEDNESDAY AS THE PERIOD OF THE HEAVIEST
RAIN AS THE ATMOSPHERIC RIVER MOVES THROUGH THE AREA FROM NORTH TO
SOUTH, WITH ADDITIONAL LIGHTER SHOWERS EXPECTED ON CHRISTMAS DAY.
RAINFALL AMOUNTS ARE STILL UNCERTAIN BUT AREAS OF THE MOUNTAINS
HAVE A 70%+ OF SEEING 2 INCHES OF RAINFALL OR MORE DURING THIS
PERIOD. THESE CHANCES RANGE FROM 25-45% ACROSS THE INLAND EMPIRE
AND WESTERN SAN DIEGO COUNTY, TO NEAR 65% CHANCE IN ORANGE COUNTY.
THE DESERTS ALSO LOOK TO RECEIVE RAIN FROM THIS WITH A 25-35%
CHANCE OF 1 INCH OR MORE IN THE LOWER DESERTS, SLIGHTLY HIGHER
CHANCES IN THE HIGH DESERT. THIS WILL LEAD TO AN INCREASED DEBRIS
FLOW AND FLOODING RISK ACROSS ALL AREAS. CONFIDENCE CONTINUES TO
INCREASE THAT SNOW LEVELS WILL BE HIGH, MAINLY ABOVE 8,000 FEET
FOR THE FIRST PART OF THE STORM SYSTEM THROUGH TUESDAY THROUGH
EARLY THURSDAY. PLEASE PLAN ACCORDINGLY IF YOU WILL BE TRAVELING
FOR THE CHRISTMAS HOLIDAY AS TRAVEL IMPACTS ARE LIKELY.
ENSEMBLE MODELS CONTINUE TO SHOW AN ACTIVE WEATHER PATTERN
CONTINUING INTO LATER NEXT WEEK. THE LOW PRESSURE SYSTEM THAT WILL
BRING THE RAIN AROUND CHRISTMAS MAY STICK AROUND FURTHER INTO
NEXT WEEK, BRINGING ADDITIONAL PERIODS OF RAINFALL AND HIGH
ELEVATION SNOW. A LOT OF THIS WILL DEPEND ON THE EXACT TRACK OF
THE LOW PRESSURE SYSTEM AND HOW COLD IT BECOMES. IF THE LOW MOVES
SLOWER AND REMAINS OFF THE COAST, ADDITIONAL PERIODS OF HEAVY
PRECIP MAY OCCUR INTO NEXT WEEKEND. IF THE LOW MOVES FASTER, WE
MAY SEE A PERIOD OF DRIER WEATHER THE DAYS FOLLOWING THE CHRISTMAS
HOLIDAY.
AVIATION
190415Z...COAST...PATCHY LOW CLOUDS/FOG HAVE DEVELOPED ALONG SAN
DIEGO COUNTY COASTAL AREAS THIS EVENING, AND WILL MOVE INTO ORANGE
CO COASTAL AREAS AND UP TO 5 MILES INLAND OVERNIGHT. CLOUDS BASES
ARE 200-500 FT MSL WITH VIS 1/4-2 SM. INTERMITTENT CIGS WITH FOG IN
AND OUT OF SITES POSSIBLE THROUGH MOST OF THE NIGHT. CLEARING TO
BEACHES 15-17Z. LOW CLOUDS MOVE BACK INLAND AFTER 01Z SAT, MOVING
FARTHER INLAND THAN TONIGHT AS BASES RISE TO 400-800 FT MSL.
OTHERWISE...SCT-BKN HIGH CLOUDS WITH UNRESTRICTED VIS TONIGHT AND
FRIDAY.
MARINE
PATCHY FOG COULD REDUCE VISIBILITY TO 1 SM LATE TONIGHT INTO FRIDAY
MORNING. OTHERWISE, NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED
THROUGH TUESDAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
UPDATE...STEWEY
PUBLIC...APR
AVIATION/MARINE...CSP
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