570
FXUS66 KSGX 110343
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
843 PM PDT WED SEP 10 2025
SYNOPSIS
A LOW PRESSURE SYSTEM MOVING INTO CALIFORNIA IS BRINGING LOWER
TEMPERATURES, WITH HIGHS FOR INLAND AREAS 10 TO 15 DEGREES BELOW
AVERAGE AGAIN ON THURSDAY. THERE WILL BE INLAND WARMING OF AROUND
5 DEGREES FOR FRIDAY AND SATURDAY WITH NOT MUCH CHANGE FOR
SUNDAY, BEFORE BETTER WARMING INTO WEDNESDAY. MONSOONAL MOISTURE
MAY MAKE A RETURN DURING THE MIDDLE AND LATTER PART OF NEXT WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
HIGH TEMPERATURES THIS AFTERNOON WERE SEVERAL DEGREES BELOW
SEASONAL AVERAGES IN THE COASTAL AREAS AND 10-15 DEGREES BELOW
AVERAGES IN THE VALLEYS, MTNS AND DESERTS. THIS EVENING, THE
MARINE LAYER IS ABOUT AS DEEP AS IT WAS YESTERDAY AT 2000-2500 FT
BUT COOLING ALOFT HAS SIGNIFICANTLY WEAKENED THE INVERSION. AS A
RESULT, THE LOW CLOUDS THIS EVENING ARE LESS EXTENSIVE AND LESS
ORGANIZED THAN AT THIS TIME YESTERDAY. THE LOW CLOUDS COULD STILL
SPREAD INLAND TO THE COASTAL SLOPES BUT THE OVERALL COVERAGE COULD
BE LESS THAN LAST NIGHT.
FROM PREVIOUS DISCUSSION...
COOLER WEATHER AND A DEEP MARINE LAYER WILL PREVAIL THE NEXT TWO
DAYS AS AN UPPER LEVEL LOW MOVES INTO CENTRAL CALIFORNIA FROM THE
NORTHWEST.
WHILE NOT AS PREVALENT AS THE PREVIOUS DAYS, A STRONGER SFC
PRESSURE GRADIENT WILL BRING GUSTIER WINDS FOR THE DESERT SLOPES
OF THE MOUNTAINS AND MOUNTAIN PASSES INTO THURSDAY MORNING,
GUSTING NEAR 50 MPH AT TIMES IN THE WIND-PRONE LOCATIONS.
850MB TEMPS WILL RANGE FROM 12-14C THROUGH THE END OF THE WEEK,
INDICATING HIGHS IN THE 60S AND 70S FOR THE COAST, VALLEYS, AND
INLAND AREAS, 60S FOR THE MOUNTAINS, AND LOW 90S FOR THE DESERTS.
AFTER AN ABOVE-NORMAL START TO SEPTEMBER, TEMPERATURES FOR THE END
OF THE WEEK WILL BE AROUND 7-15 DEGREES BELOW NORMAL. BY FRIDAY,
A WEAK RIDGE IN BETWEEN TWO LOWS WILL INCH INLAND, PUSHING THE LOW
UP INTO IDAHO/MONTANA. THE THERMAL RIDGE AXIS WILL BE POSITIONED
OVER CALIFORNIA BY SATURDAY, RETURNING THE REGION TO A WARMING
TREND, ALTHOUGH HIGHS MAY STILL BE SLIGHTLY BELOW NORMAL. BEFORE
THE WARMER WEATHER CAN DOMINATE, A SHORTWAVE TROUGH OFF THE COAST
OF LA WILL MOVE EASTWARD INTO CALIFORNIA EARLY SUNDAY, DAMPENING
THE INFLUENCE OF THE WEAK RIDGE. THEREFORE, HIGHS ON SUNDAY WILL
LIKELY REMAIN SIMILAR TO SATURDAY, IN THE 70S FOR COASTAL AREAS,
LOW TO MID 80S FOR INLAND AREAS, 70S FOR THE MOUNTAINS, AND UPPER
90S FOR DESERTS. AS THE SHORTWAVE BREAKS DOWN ON MONDAY,
TEMPERATURES WILL BE ABLE TO WARM A BIT OVER SUNDAY.
MODEL SOLUTIONS BEGIN TO DIVERGE HEADING INTO EARLY NEXT WEEK.
THERE IS DECENT CONSENSUS ON A LOW OVER THE PACNW COMING DOWN INTO
NEVADA WITH ADDITIONAL WEAK RIDGING ON THE BACK SIDE OF THIS.
SHOULD THIS OCCUR, A WARMING TREND SHOULD SETTLE ACROSS THE REGION
INTO THE MIDDLE OF THE WEEK WITH HIGHS POTENTIALLY REACHING ABOVE
NORMAL BY WEDNESDAY. OTHER MODELS INDICATE BETTER CHANCES FOR
ZONAL FLOW ALOFT HEADING INTO MID-WEEK, STILL INDICATING A RETURN
TO WARMER WEATHER, WITH LIKELY A SLOWER UPTICK IN TEMPERATURES.
MODELS CONTINUE TO HINT AT THE RETURN OF SOME MONSOONAL MOISTURE
AS EARLY AS MID NEXT WEEK, BUT CONFIDENCE IN THIS REMAINS LOW
UNTIL BETTER ALIGNMENT IS SEEN IN THE MODELS. FOR NOW, DRY
CONDITIONS WILL LIKELY PREVAIL FOR THE FORECAST PERIOD WITH
GENERALLY BELOW AVERAGE TEMPERATURES.
AVIATION
110315Z...COAST/VALLEYS...LOW CLOUDS WITH VARYING BASES OF 1500
TO 2500 FEET MSL WILL CONTINUE TO DEVELOP AND MOVE INLAND
THROUGHOUT THE EVENING, EVENTUALLY FILLING INTO THE COASTAL BASIN
AND INLAND EMPIRE BY 12Z THUR. PATCHY AND INTERMITTENT SCATTERING
OF SKY CONDITIONS WILL BE POSSIBLE AT TIMES WITH CLOUDS BEGINNING
TO CLEAR OVER INLAND AREAS AROUND 15Z-17Z, THEN COASTAL AREAS
17-20Z THUR. CLOUDS WILL BEGIN TO REFORM AND FILL IN ALONG THE
COASTAL SITES AROUND 23-01Z FRI, AND THEN FILL INTO THE INLAND
AREAS BY 04-06Z FRI, WITH SLIGHTLY LOWER BASES.
MOUNTAINS/DESERTS...VFR CONDITIONS PREVAIL THROUGH FRIDAY. STRONG
WINDS OF 25-30KT WITH GUSTS UP TO 40KT THROUGH 08Z THUR IN THE
MOUNTAIN PASSES INTO ADJACENT DESERTS, CAUSING LLWS AND
UP/DOWNDRAFTS IN POCKETS IN LEE OF MOUNTAINS.
MARINE
NO 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...PG
AVIATION/MARINE...STEWEY
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page