636
FXUS66 KSGX 220536
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
1036 PM PDT MON SEP 21 2026
SYNOPSIS
MINIMAL CHANGE IN TEMPERATURES EXPECTED FOR THE END OF THE WEEK
INTO THE WEEKEND. A DEEP MARINE LAYER WILL BE MAINTAINED INTO
TUESDAY MORNING WITH NIGHT AND MORNING LOW CLOUDS SPREADING INTO
THE VALLEYS. THERE IS A A SLIGHT CHANCE OF SHOWERS AND ISOLATED
THUNDERSTORMS OVER THE MOUNTAINS THURSDAY AFTERNOON, WITH
OTHERWISE DRY CONDITIONS EXPECTED TO PREVAIL.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
..UPDATED AVIATION DISCUSSION
UNDER THE INFLUENCE OF THE LOW, THE MARINE LAYER WILL STAY 3000
TO 3500 FT DEEP INTO TUESDAY MORNING WITH LOW CLOUDS EXPECTED TO
FILL IN MUCH OF THE COASTAL BASIN OVERNIGHT.
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 5
TO 10 DEGREES WARMER FOR THE INLAND EMPIRE AND INLAND ORANGE
COUNTY. WITH THE WARMING, HIGH TEMPERATURES ON WEDNESDAY WILL BE
WITHIN A FEW DEGREES OF AVERAGE FOR MOST AREAS. ANOTHER FEW
DEGREES OF WARMING IS EXPECTED THURSDAY AND FRIDAY WITH
TEMPERATURES ALONG THE COAST WITH THE HIGHEST DEPARTURE FROM
NORMAL AT 7 TO 12 DEGREES. FOR THE LATTER HALF OF THE WEEK,
OVERNIGHT LOWS WILL INCREASE TO THE MID-60S TO 70 WEST OF THE
MOUNTAINS AND IN THE UPPER 70S TO LOW 80S IN THE LOW DESERT.
FOR THURSDAY, A CLOSED LOW LINGERING TO OUR SOUTHWEST WILL START TO
MOVE EAST. THIS LOW WILL HAVE SOME UPPER LEVEL MOISTURE ENTRAINED IN
IT WHICH MAY BRING SOME PRECIPITATION TO THE AREA, MOST LIKELY FOR
THE MOUNTAINS. THE LOW WILL BRING SOME INCREASE IN INSTABILITY, SO A
SLIGHT CHANCE OF ISOLATED THUNDERSTORMS (15-20%) HAS BEEN INTRODUCED
TO THE FORECAST, MAINLY CONFINED TO THE MOUNTAINS. THERE IS LOW
CONFIDENCE IN ANY POTENTIAL IMPACTS, ESPECIALLY IN THE WAY OF
FLOODING. THE SPREAD IN NBM GUIDANCE BETWEEN 10TH PERCENTILE AND
90TH PERCENTILE FOR 24 HOUR RAINFALL IS 0 AND 0.55 INCHES
RESPECTIVELY.
TROPICAL CYCLONE 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 EARLY
SATURDAY. THERE REMAINS A LOT OF UNCERTAINTY IN THE FORECAST FOR
LATE IN THE WEEKEND INTO NEXT WEEK BUT THERE COULD EVENTUALLY BE
AT LEAST SOME PERIPHERAL IMPACTS TO PORTIONS OF SOUTHERN
CALIFORNIA.
AVIATION
220530Z...COAST/VALLEYS...LOW CLOUDS WITH BASES 1800-3800 FEET MSL
WILL GRADUALLY INCREASE TO PRODUCE CIGS AROUND 2000-2500 FEET MSL
OVER MOST OF THE COASTAL BASIN. RELATIVELY EARLY SCATTER OUT VCNTY
KSAN 14-16Z TUESDAY, AND 15-18Z ELSEWHERE. LOW CLOUDS BASED AROUND
1500-2000 FEET MSL TO DEVELOP VCNTY KSAN AFTER 03Z TUESDAY EVENING.
OTHERWISE...MOSTLY CLEAR SKIES THROUGH TUESDAY.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH SATURDAY.
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...CO
AVIATION/MARINE...MM
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