689
FXUS66 KSGX 161558
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
858 AM PDT TUE SEP 16 2025
SYNOPSIS
REMNANTS OF TROPICAL STORM MARIO WILL BRING INCREASING MOISTURE AND
CLOUDS TO THE AREA FOR THE MIDDLE OF THE WEEK. THERE ARE CHANCES OF
SHOWERS AND THUNDERSTORMS FOR THE MOUNTAINS AND DESERTS FROM THIS
AFTERNOON THROUGH EARLY NEXT WEEK. FOR WEDNESDAY THROUGH FRIDAY
MORNING THERE ARE CHANCES FOR SHOWERS AND THUNDERSTORMS WEST OF THE
MOUNTAINS. THE MARINE LAYER WILL BECOME SHALLOWER WITH THE POTENTIAL
FOR MINIMAL OR NO LOW CLOUD COVERAGE FOR THE MIDDLE TO END OF THE
WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
VISIBLE SATELLITE AT 9 THIS MORNING WAS SHOWING LOW CLOUDS CLEARING
ALONG THE IMMEDIATE COAST, WITH A SWATH OF HIGH CLOUDS MOVING INTO
IMPERIAL COUNTY. THE 12Z KNXK SOUNDING WAS SHOWING 1.25 INCHES OF
PRECIPITABLE WATER WITH 700 J/KG OF MOST UNSTABLE CAPE. WITH THE
INCREASE IN MOISTURE AND INSTABILITY, THERE IS THE SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS MAINLY OVER THE MOUNTAINS THIS AFTERNOON.
ONE INHIBITING FACTOR IS A FAIRLY SUBSTANTIAL INVERSION NEAR 700 MB.
THIS COULD LIMIT CONVECTIVE DEVELOPMENT, EVEN WITH THE OTHERWISE
FAVORABLE CONDITIONS.
CHANCES FOR SHOWERS AND THUNDERSTORMS BECOME MORE WIDESPREAD FOR
WEDNESDAY AFTERNOON THROUGH EARLY FRIDAY MORNING. IT LOOKS LIKE
THERE WILL BE ENOUGH MOISTURE AND INSTABILITY TOMORROW AFTERNOON FOR
THUNDERSTORMS TO DEVELOP OVER THE MOUNTAINS, LOCALLY INTO THE
DESERTS AHEAD OF THE MAIN MOISTURE SURGE. AS WE MOVE INTO WEDNESDAY
EVENING AND THURSDAY MORNING, SHOWER CHANCES BECOME MORE WIDESPREAD
WEST OF THE MOUNTAINS, WITH THE POTENTIAL FOR ISOLATED THUNDERSTORMS
TO DEVELOP. SHOWER COVERAGE OVERNIGHT MAY BE FAIRLY SCATTERED. FOR
THURSDAY AFTERNOON, SHOWER AND THUNDERSTORM CHANCES CONTINUE FOR THE
INLAND VALLEYS, MOUNTAINS, AND DESERTS. DEPENDING ON HOW STRONG THE
EASTERLY FLOW IS, IT'S POSSIBLE THUNDERSTORMS COULD DRIFT CLOSER TO
THE COAST. FLASH FLOODING IS POSSIBLE WHERE THUNDERSTORMS DEVELOP,
ESPECIALLY IN THE MOUNTAINS AND DESERTS. OTHERWISE, MAIN IMPACTS
WILL BE FREQUENT LIGHTNING AND THE POTENTIAL FOR URBAN FLOODING
WHERE SHOWERS/THUNDERSTORMS DEVELOP WEST OF THE MOUNTAINS. NBM
CHANCES FOR ONE-HALF INCH OR MORE OF RAINFALL IS AROUND 25 PERCENT
FOR THE COAST AND VALLEYS TO AROUND 45 TO 55 PERCENT FOR THE
MOUNTAINS.
HIGH RESOLUTION GUIDANCE IS INDICATING SOME LINGERING ISOLATED
HEAVIER SHOWERS OR THUNDERSTORMS OVERNIGHT THURSDAY INTO FRIDAY
MORNING. FOR FRIDAY, IT LOOKS LIKE THE BEST CHANCES OF SHOWERS AND
THUNDERSTORMS WILL BE OVER THE MOUNTAINS POTENTIALLY INTO THE
DESERTS. CHANCES FOR AFTERNOON SHOWERS AND THUNDERSTORMS WILL
CONTINUE FOR THE MOUNTAINS AND DESERTS INTO EARLY NEXT WEEK.
TODAY WILL BE WARMER WITH HIGH TEMPERATURES FOR THE COAST AND
VALLEYS AROUND 4 TO 8 DEGREES ABOVE AVERAGE WITH THE DESERTS A FEW
DEGREES ABOVE AVERAGE. HIGH TEMPERATURES WILL RANGE FROM AROUND 80
NEAR THE COAST TO THE MID 90S TO 102 FOR THE INLAND EMPIRE WITH 100
TO 105 FOR THE LOWER DESERTS. THE INCREASE IN MOISTURE AND CLOUDS,
WEDNESDAY AND THURSDAY WILL RESULT IN HIGH TEMPERATURES FOR INLAND
AREAS TO COOL SEVERAL DEGREES. HIGH TEMPERATURES ON THURSDAY WILL BE
AS MUCH AS 8 TO 12 DEGREES BELOW AVERAGE FOR THE MOUNTAINS.
THERE COULD BE ANOTHER INFLUX OF TROPICAL MOISTURE EARLY NEXT WEEK
FROM A SECOND TROPICAL SYSTEM. HIGH TEMPERATURES FOR INLAND AREAS
WILL WARM AROUND 10 DEGREES FROM THURSDAY THROUGH SUNDAY WITH SUNDAY
HIGH TEMPERATURES MOSTLY A FEW TO AROUND 5 DEGREES BELOW AVERAGE.
HIGH TEMPERATURES ON SUNDAY WILL RANGE FROM THE MID 70S NEAR THE
COAST TO THE UPPER 80S TO MID 90S FOR THE INLAND EMPIRE WITH THE MID
90S TO AROUND 100 FOR THE LOWER DESERTS.
AVIATION
161530Z...COAST...LOW CLOUDS GENERALLY NOT EXPECTED TONIGHT INTO
WEDNESDAY WITH LOW TO MODERATE CONFIDENCE. CLOUDS WILL BE VERY
PATCHY WITH BASES 300-700 FEET MSL. IF ANY CLOUDS FORM, THEY WILL
FORM BETWEEN 08-17Z WED.
VALLEYS/MOUNTAINS/DESERTS...VFR CONDITIONS TODAY AND TONIGHT. CLOUDS
OVER MOUNTAINS DEVELOPING AFTER 18Z AND LEADING TO A SLIGHT CHANCE
TSRA 21-01Z. CB BASES AOA 10000 FEET MSL, WITH TOPS REACHING 30000
FEET MSL. LIGHTNING, GUSTY WINDS, AND REDUCED VIS EXPECTED WHERE ANY
TSRA DEVELOPS.
REGIONWIDE...SCT CLOUDS BECOMING BKN AROUND 10000 FEET MSL
AFTER 00Z THROUGH MUCH OF WEDNESDAY.
MARINE
THERE IS A SLIGHT CHANCE OF THUNDERSTORMS WEDNESDAY
THROUGH FRIDAY, WITH THE GREATEST CHANCE ON THURSDAY AFTERNOON AND
EVENING. ANY STORMS COULD BRIEFLY PRODUCE LIGHTNING, GUSTY WINDS AND
CHOPPY SEAS. OTHERWISE, NO ADDITIONAL MARINE WEATHER HAZARDS 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...APR
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