471
FXUS66 KSGX 210859
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
159 AM PDT MON SEP 21 2026
SYNOPSIS
A WEAK LOW PRESSURE SYSTEM MOVING INLAND THROUGH CENTRAL AND
SOUTHERN CALIFORNIA TODAY WILL BRING A FEW MORE DEGREES OF
COOLING AND MAINTAIN A MARINE LAYER DEEP ENOUGH FOR NIGHT AND
MORNING COASTAL LOW CLOUDS TO COVER MUCH FOR THE COAST AND VALLEYS
INTO TUESDAY MORNING. STRENGTHENING HIGH PRESSURE TO THE EAST AND
WEAK OFFSHORE FLOW IN THE MOUNTAINS FOR WEDNESDAY AND THURSDAY
WILL BRING WARMING OF HIGH TEMPERATURES TO WITHIN A FEW DEGREES
OF AVERAGE ON WEDNESDAY WITH MORE GRADUAL WARMING FOR THURSDAY
INTO THE WEEKEND.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
SHORT TERM (TODAY THROUGH WEDNESDAY)
A WEAK UPPER LEVEL LOW PRESSURE SYSTEM WILL MOVE INLAND THROUGH
CENTRAL AND SOUTHERN CALIFORNIA TODAY WITH HIGH TEMPERATURES A FEW
TO AROUND 5 DEGREES COOLER THAN SUNDAY AND AS MUCH AS 5 TO 10
DEGREES BELOW AVERAGE FOR THE VALLEYS. HIGH TEMPERATURES FOR TODAY
WILL RANGE FROM THE LOWER TO MID 70S NEAR THE COAST TO THE LOWER
80S FOR THE INLAND EMPIRE WITH THE LOWER DESERTS IN THE MID TO
UPPER 90S.
THE UPPER LEVEL LOW PRESSURE SYSTEM WILL WEAKEN AND MOVE EAST ON
TUESDAY WITH HIGH PRESSURE TO THE EAST STRENGTHENING FOR WEDNESDAY
INTO NEXT WEEKEND. THERE WILL BE EAST WINDS GUSTING TO 15 TO 25
MPH FOR THE MOUNTAINS DURING THE MORNING ON WEDNESDAY AND
THURSDAY.
HIGH TEMPERATURES ON TUESDAY WILL WARM A FEW TO AROUND 5 DEGREES
WITH THE GREATEST WARMING FOR THE INLAND VALLEYS. WARMING WILL
CONTINUE ON WEDNESDAY WITH HIGH TEMPERATURES AS MUCH AS ANOTHER 4
TO 8 DEGREES WARMER FOR THE INLAND EMPIRE. WITH THE WARMING, HIGH
TEMPERATURES ON WEDNESDAY WILL BE WITHIN A FEW DEGREES OF AVERAGE
FOR MOST AREAS. HIGH TEMPERATURES ON WEDNESDAY WILL RANGE FROM THE
MID TO UPPER 70S NEAR THE COAST TO THE UPPER 80S TO MID 90S FOR
THE INLAND EMPIRE WITH THE LOWER DESERTS AROUND 100.
THE MARINE LAYER WILL REMAIN AROUND 3000 TO 3500 FEET DEEP INTO
TUESDAY MORNING WITH NIGHT AND MORNING COASTAL LOW CLOUDS
SPREADING INLAND ACROSS MOST OF THE COAST AND VALLEYS OVERNIGHT.
THE MARINE LAYER WILL BECOME SHALLOWER ON WEDNESDAY AND THURSDAY
WITH COASTAL LOW CLOUDS NOT SPREADING NEARLY AS FAR INTO THE
VALLEYS.
LONG TERM (THURSDAY THROUGH SUNDAY)
HIGH PRESSURE ALOFT WILL REMAIN ACROSS NORTHERN MEXICO AND
ADJACENT SOUTHWEST STATES THROUGH THE WEEKEND WITH HIGH
TEMPERATURES WARMING TO AROUND 5 DEGREES ABOVE AVERAGE FOR
THURSDAY AND FRIDAY, AND POSSIBLY TO 5 TO 10 DEGREES ABOVE AVERAGE
FOR THE COAST AND VALLEYS ON SATURDAY WITH AN INCREASE IN SURFACE
DEWPOINTS INTO THE MID TO UPPER 60S FOR COASTAL AREAS ON SATURDAY.
TROPICAL STORM POLO, OFF THE SOUTHWEST COAST OF MEXICO, IS
FORECAST BY THE NATIONAL HURRICANE CENTER TO BECOME A MAJOR
HURRICANE OVER THE NEW FEW DAYS WITH A TRACK EVENTUALLY AND
GENERALLY TOWARD THE WEST NORTHWEST WHICH MIGHT PUT THE CENTER A
FEW HUNDRED MILES SOUTH OF THE SOUTHERN TIP OF BAJA ON LATE FRIDAY
AFTERNOON. THE TRACK UNCERTAINTY IS EVEN GREATER BEYOND FRIDAY.
THERE COULD EVENTUALLY BE AT LEAST SOME PERIPHERAL IMPACTS TO
PORTIONS OF SOUTHERN CALIFORNIA FOR LATE IN THE WEEKEND INTO EARLY
NEXT WEEK.
AVIATION... 210600Z...COAST/VALLEYS
LOW CLOUDS WITH BASES AROUND
2500 FEET MSL WILL CONTINUE TO GRADUALLY FILL MUCH IF NOT ALL OF THE
COASTAL BASIN OVERNIGHT. CLOUDS CLEAR AROUND 17-20Z. PATCHY LOW
CLOUDS COULD PERSIST NEAR THE COAST THEREAFTER. LOW CLOUDS WITH
SIMILAR BASES WILL INCREASE IN COVERAGE AFTER 23Z MONDAY.
MOUNTAINS/DESERTS...BKN CLOUDS AOA 15000 FEET MSL WILL GRADUALLY
CLEAR FROM WEST TO EAST OVERNIGHT. MOSTLY CLEAR SKIES WITH
UNRESTRICTED VIS MONDAY.
MARINE
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...17
AVIATION/MARINE...MM
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