795
FXUS66 KSGX 172055
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
155 PM PDT THU SEP 17 2026
SYNOPSIS
HIGH TEMPERATURES FOR TODAY WILL REMAIN AS MUCH AS 5 TO 10 DEGREES
BELOW AVERAGE FOR THE INLAND VALLEYS THANKS TO THE MARINE LAYER
STRETCHING WELL INLAND. A SLIGHT WARMING AND DRYING TREND INTO
THIS WEEKEND TAKES TEMPERATURES BACK TO NEAR NORMAL FOR SATURDAY
AND SUNDAY AS THE MARINE LAYER BECOMES GRADUALLY SHALLOWER. AFTER
A BRIEFLY COOLER DAY ON MONDAY, ANOTHER WARMING TREND WILL BEGIN
NEXT TUESDAY WITH HIGH TEMPERATURES RETURNING ABOVE AVERAGE BY
WEDNESDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
TODAY THROUGH THIS WEEKEND...
CURRENT SATELLITE AND 500MB RAP ANALYSIS THIS AFTERNOON REVEALS A
POTENT UPPER LOW CENTERED ACROSS NORTHERN CALIFORNIA THIS AFTERNOON.
THIS FEATURE IS INDUCING LOW THICKNESS AND SOUTHWESTERLY FLOW ALOFT,
WHICH IS FUELING THE BELOW AVERAGE TEMPERATURES SEEN THE LAST FEW
DAYS. HIGHS THIS AFTERNOON ARE RUNNING AROUND 10 DEGREES BELOW
NORMAL FOR THE INLAND AREAS. A VERY DEEP MARINE LAYER HAS ALSO
RESULTED FROM THE INFLUENCE OF THE NEARBY UPPER LOW, WHICH SPREAD
WELL THROUGH THE COASTAL MOUNTAIN SLOPES, WITH EVEN ISOLATED
INSTANCES OF DRIZZLE ALONG THE COAST THIS MORNING. AS WE PROGRESS
INTO THIS WEEKEND, THIS UPPER LOW WILL GRADUALLY KICK EAST TOWARDS
THE NORTHERN ROCKIES, ALLOWING A WEAK UPPER RIDGE TO PASS THROUGH.
THIS WILL BRING A SUBTLE WARMING TREND TO THE REGION, BRINGING
TEMPERATURES BACK TO NEAR NORMAL FOR SATURDAY/SUNDAY. THIS PASSING
RIDGE WILL ALSO SERVE TO SQUISH DOWN THE MARINE LAYER SOME,
RESTRICTING CLOUD COVER TOWARDS THE COASTS AND WESTERN VALLEYS.
MONDAY THROUGH MIDWEEK...
FOLLOWING THE SUBTLE WEEKEND WARMUP, ANOTHER WEAK TROUGH IS SET TO
SWING THROUGH MONDAY/TUESDAY. THIS WILL KNOCK TEMPERATURE BACK DOWN
A FEW DEGREES, BACK TO COOLER THAN SEASONAL NORMS, FOR MONDAY AND
TUESDAY. BEYOND TUESDAY, MODELS BEGIN TO DIVERGENCE IN THE
RESOLUTION OF THE UPPER RIDGE ACROSS THE SOUTH-CENTRAL UNITED
STATES. SOME ENSEMBLE CLUSTERS FAVOR A STRONGER RIDGE THAT CAN PUSH
FURTHER WEST, WITH OTHER CLUSTERS KEEPING THE RIDGE WEAKER AND
FURTHER EAST. THIS IS LEADING TO A FAIRLY LARGE SPREAD IN
TEMPERATURES COME MID NEXT WEEK, THOUGHT THE NBM MEAN IS FAVORING A
WARMING TREND THAT BRINGS TEMPERATURES AROUND 5 DEGREES NORMAL FOR
WEDNESDAY.
AVIATION
171800Z...COAST/VALLEYS...LOW CLOUDS AROUND 3000-4000 FEET MSL
CONTINUE TO SCATTER OUT THROUGH ABOUT 19Z. LOW CLOUDS BASED AROUND
2000-3000 FEET MSL WILL RETURN INTERMITTENTLY TO KSAN AND KCRQ BY 23-
03Z BEFORE BECOMING MORE CONSISTENT/WIDESPREAD AND SPREADING NORTH
AND INTO THE ENTIRE COASTAL BASIN BY 12Z FRIDAY. SIMILAR TO THIS
MORNING, CLOUDS LIFT THEN SCATTER 16-18Z.
MOUNTAINS/DESERTS...MOSTLY CLEAR AND VFR CONDITIONS TODAY AND
TONIGHT.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH MONDAY.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
PUBLIC...MUNYAN
AVIATION/MARINE...CSP
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