832
FXUS66 KSGX 020434
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
934 PM PDT WED OCT 1 2025
SYNOPSIS
MINOR WARMING ON THURSDAY. A TROUGH WILL MOVE INTO THE WEST
COAST, BRINGING BELOW NORMAL TEMPERATURES AND BREEZY WEST WINDS
ACROSS THE MOUNTAINS AND THE DESERTS ON FRIDAY. MINOR WARMING WEST
OF THE MOUNTAINS ON SATURDAY AS WEAK OFFSHORE FLOW DEVELOPS. LOW
PRESSURE FROM THE NORTH WILL SPREAD MORE COOLING INLAND FOR SUNDAY
AND MONDAY WITH TUESDAY A FEW DEGREES WARMER.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
PATCHY LOW CLOUDS ARE DEVELOPING OVER COASTAL SAN DIEGO COUNTY,
WITH CLEAR SKIES ELSEWHERE. THE 00Z HREF HAS FAIRLY HIGH
PROBABILITIES (60-80%) OF LOW CLOUDS ACROSS ALL OF THE COASTAL
AREAS AND FAR WESTERN VALLEYS BY THURSDAY MORNING. FOR THURSDAY,
AN UPPER LEVEL TROUGH WILL AMPLIFY OFF THE WEST COAST, FORCING
DOWNSTREAM RIDGING OVER THE DESERT SOUTHWEST. SO CAL WILL BE
WEDGED BETWEEN THE TWO, ALLOWING FOR THE MINOR WARMING TREND TO
CONTINUE. THE TROUGH OFF THE COAST DEEPENS AND MOVES INLAND ACROSS
CA ON FRIDAY INTO EARLY SATURDAY, BRINGING COOLER WEATHER AND
WEST WINDS GUSTING 35-45 MPH IN THE MOUNTAINS AND DESERTS,
STRONGEST BELOW THE SAN GORGONIO PASS. THE MARINE LAYER WILL ALSO
DEEPEN THURSDAY NIGHT INTO FRIDAY MORNING WITH LOW CLOUDS
EXTENDING INTO THE INLAND VALLEYS.
SURFACE HIGH PRESSURE BUILDS BEHIND THE DEPARTING TROUGH ON
SATURDAY. GRADIENTS TURN WEAKLY OFFSHORE TO THE NORTH, AND THE
CW3E WRF PROBABILITIES OF A WEAK SANTA ANA EVENT HAVE INCREASED TO
AROUND 50% FOR SATURDAY MORNING. WITH THE LACK OF UPPER SUPPORT,
WINDS WILL MOSTLY BE CONFINED TO THE CAJON PASS AND SANTA ANA
MOUNTAINS. THE OFFSHORE FLOW WILL HELP CLEAR OUT LOW CLOUDS AND
PROVIDE A FEW DEGREES OF WARMING WEST OF THE MOUNTAINS ON
SATURDAY.
A SECOND LOW DROPS SOUTH AND DEEPENS SUNDAY INTO MONDAY FOR
ANOTHER COOLING TREND AND A RETURN OF ONSHORE FLOW. ENSEMBLES
CONTINUE TO SHOW THIS TROUGH TAKING AN INLAND TRACK, LACKING
MOISTURE FOR ANY MEANINGFUL PRECIPITATION. THE MARINE LAYER
DEEPENING ENOUGH FOR ANY DRIZZLE IS PROBABLY THE BEST WE'LL BE
ABLE TO DO, AND EVEN THAT IS QUESTIONABLE. THE TROUGH LINGERS AND
WEAKENS AS HIGH PRESSURE TRIES TO BUILD IN FROM THE EAST, BRINGING
ANOTHER MINOR WARMING TREND TOWARDS THE MIDDLE OF NEXT WEEK.
AVIATION
020330Z....COASTS/VALLEYS...PATCHY LOW CLOUDS BASED 1000-1500 FT MSL
HAVE STARTED TO DEVELOP OVER SAN DIEGO COUNTY COASTS AND VALLEYS.
COVERAGE REMAINING PATCHY THROUGH 08-09Z WITH TEMPO CIGS FOR KSAN
AND KCRQ. GREATER COVERAGE OF LOW CLOUDS THEREAFTER WITH 15-20 MILES
OF INLAND EXTENT. CLOUDS MAY EXTEND INTO THE WESTERN/SOUTHERN INLAND
EMPIRE 12-16Z. LOW CONFIDENCE (20-30% CHANCE) FOR PATCHY VIS
REDUCTIONS IN VALLEYS NEAR I-15 AND I-215 DUE TO BR/HZ/FG.
SCATTERING TOWARD THE COAST FROM 15-17Z THU. SKC THROUGH THE
AFTERNOON. LOW CLOUDS WITH SLIGHTLY HIGHER BASES RETURN TO COASTAL
AREAS 03-06Z FRIDAY.
MOUNTAINS/DESERTS...MOSTLY CLEAR AND VFR CONDITIONS THROUGH THURSDAY
EVENING.
MARINE
NORTHWEST WINDS FRIDAY AFTERNOON OVER OUTER WATERS NEAR SAN CLEMENTE
ISLAND WILL BE SUSTAINED NEAR 20 KTS. STRONG WINDS WILL CAUSE FOR
DANGEROUS CONDITIONS FOR SMALL CRAFT. NO OTHER HAZARDOUS MARINE
CONDITIONS ARE EXPECTED THROUGH SUNDAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
PUBLIC...SS
AVIATION/MARINE...KW
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