386
FXUS66 KSGX 201626
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
926 AM PDT MON OCT 20 2025
SYNOPSIS
ABOVE AVERAGE HIGH TEMPERATURES WILL CONTINUE FOR INLAND AREAS
THROUGH TUESDAY WHILE WEAK ONSHORE FLOW BEGINS TO SPREAD COOLING
INTO COASTAL AREAS AS A SHALLOW MARINE LAYER SLOWLY DEEPENS. MUCH
COOLER ON WEDNESDAY WITH THE MARINE LAYER DEEPENING FURTHER.
WARMER AGAIN ON THURSDAY AND FRIDAY, WITH FRIDAY HIGH TEMPERATURES
AROUND 5 DEGREES ABOVE AVERAGE FOR INLAND AREAS. COOLER AGAIN WITH
STRONGER ONSHORE FLOW FOR NEXT WEEKEND.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THIS MORNING...THE MARINE LAYER REMAINS VERY SHALLOW UNDER A
NARROW UPPER LEVEL RIDGE SANDWICHED BETWEEN A CLOSED UPPER LOW TO
THE SOUTHWEST AND AN EXTENSIVE TROUGH OVER CENTRAL CONUS. PATCHY
LOW CLOUDS AND FOG IN THE COASTAL AREAS ARE CLEARING AT THIS HOUR.
THE HIGH PRESSURE RIDGE OVER SOCAL WILL KEEP DAYTIME HIGH TEMPS A
FEW DEGREES ABOVE SEASONAL AVERAGES FOR INLAND AREAS THROUGH
TUESDAY. A SHALLOW MARINE LAYER AND WEAK ONSHORE FLOW WILL KEEP
TEMPS NEAR OR A LITTLE BELOW AVERAGES IN THE COASTAL AREAS. PATCHY
LOW CLOUDS AND FOG WILL RETURN LATE TONIGHT INTO TUE MORNING,
SPREADING A LITTLE FARTHER INLAND AS THE MARINE LAYER SLOWLY
DEEPENS.
THE CLOSED UPPER LOW TO THE SOUTHWEST WILL MOVE INLAND OVER SOCAL
TUE NIGHT/WED. THIS WILL BRING SIGNIFICANT COOLING, STRONGER ONSHORE
FLOW AND A DEEPENING MARINE LAYER FOR WEDNESDAY. WED HIGH TEMPS
WILL BE AS MUCH AS 12 TO 18 DEGREES COOLER THAN TUE IN THE MTNS
AND DESERTS, AND ABOUT 5 TO 10 DEGREES BELOW SEASONAL AVERAGES FOR
THE MOUNTAINS AND VALLEYS. DAYTIME HIGH TEMPS WILL RANGE FROM THE
MID TO UPPER 60S NEAR THE COAST TO THE UPPER 60S TO MID 70S FOR
THE INLAND EMPIRE WITH THE LOWER TO MID 80S FOR THE LOWER DESERTS.
THE MARINE LAYER WILL DEEPEN SIGNIFICANTLY, ENABLING LOW CLOUDS TO
COVER MOST OF THE REGION WEST OF THE MTNS WED MORNING.
PRECIPITATION IS UNLIKELY WITH THIS SYSTEM BUT MORNING DRIZZLE
FROM THE DEEPENING MARINE LAYER LOW CLOUDS CAN'T BE RULED OUT.
FOR THU AND FRI...AS THE UPPER LOW MOVES EAST INTO THE ROCKIES,
HIGH PRESSURE RIDGING WILL MOVE IN FROM THE WEST. THIS WILL BRING WARMING
FOR THURSDAY AND FRIDAY, WITH HIGH TEMPERATURES ON THURSDAY RISING
BY AS MUCH AS 10 DEGREES IN THE MOUNTAINS AND INLAND VALLEYS.
ADDITIONAL WARMING OF ANOTHER 2 TO 5 DEGREES FOR MOST AREAS ON
FRIDAY. FRIDAY HIGH TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE
AVERAGE FOR INLAND AREAS AND WILL RANGE FROM THE LOWER 70S NEAR
THE COAST TO THE LOWER TO MID 80S FOR THE INLAND EMPIRE, AND THE
LOWER 90S FOR THE LOWER DESERTS. THE MARINE LAYER WILL ALSO BECOME
SHALLOWER, WITH LOW CLOUDS RETREATING TO THE COASTAL AREAS ONCE
AGAIN.
FOR NEXT WEEKEND, A LOW PRESSURE SYSTEM MOVING INLAND TO THE
NORTH WILL STRENGTHEN THE ONSHORE FLOW ACROSS SOUTHERN
CALIFORNIA. THIS WILL AGAIN SPREAD COOLING INLAND, WITH HIGH
TEMPERATURES NEXT SUNDAY A FEW TO AROUND 5 DEGREES BELOW AVERAGE.
HIGH TEMPERATURES FOR NEXT SUNDAY WILL RANGE FROM AROUND 70 NEAR
THE COAST TO THE LOWER TO MID 70S FOR THE INLAND EMPIRE WITH THE
MID 80S FOR THE LOWER DESERTS. THE MARINE LAYER WILL AGAIN DEEPEN
ALLOWING LOW CLOUDS TO SPREAD INTO THE INLAND VALLEYS AND
FOOTHILLS.
AVIATION
201530Z....COAST...FEW-SCT LOW CLOUDS AND FOG CONTINUE TO RETREAT
THROUGH 17Z. AREAS OF LOW CLOUDS AND FOG RETURN AFTER 06Z TONIGHT,
INCREASING IN COVERAGE INTO TUESDAY. OTHERWISE, VFR CONDITIONS ARE
EXPECTED.
VALLEYS/MOUNTAINS/DESERTS...CLEAR SKIES WITH VFR CONDITIONS THROUGH
THE TAF PERIOD.
MARINE
LINGERING PATCHY FOG THIS MORNING SHOULD CLEAR BY 10AM WITH PATCHY
FOG TO REDUCE VISIBILITY TUESDAY MORNING. OTHERWISE, NO HAZARDOUS
MARINE CONDITIONS ARE EXPECTED THROUGH FRIDAY.
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...VILLAFANE
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page