337
FXUS66 KSGX 151025
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
325 AM PDT MON SEP 15 2025
SYNOPSIS
GRADUAL WARMING THROUGH MID-WEEK, WITH GRADUAL COOLING FOR THE
SECOND HALF OF THE WEEK. AN INFLUX OF TROPICAL MOISTURE WILL BRING
CHANCES OF SHOWERS AND THUNDERSTORMS FOR WEDNESDAY INTO NEXT
WEEKEND. HIGHEST CHANCES OF SHOWERS AND THUNDERSTORMS WILL BE IN
THE MOUNTAINS AND DESERTS, WITH LESSER CHANCES WEST OF THE
MOUNTAINS. THE MARINE LAYER WILL BECOME SHALLOWER EARLY IN THE
WEEK, 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...
THIS MORNING...THE MARINE LAYER IS SHALLOWER THAN YESTERDAY UNDER
A WEAK HIGH PRESSURE RIDGE DOWNSTREAM FROM A CLOSED UPPER LOW
ABOUT 385 MILES SOUTHWEST OF SAN DIEGO. LOW CLOUDS ARE ALREADY
COVERING THE COASTAL AREAS AND HAVE SPREAD UP TO 15 MILES INLAND,
WITH FOG ON THE ELEVATED INLAND TERRAIN. WE CAN EXPECT TO SEE
SIMILAR LOW CLOUD CLEARING TO YESTERDAY MORNING. THE WARMING TREND
WILL CONTINUE TODAY, MOST NOTICEABLE INLAND WITH TEMPERATURES UP
TO 5 DEGREES ABOVE SEASONAL AVERAGES IN THE INLAND VALLEYS. HIGH
TEMPS IN THE IE AND HIGH DESERTS WILL REACH THE LOW TO MID 90S,
LOW 100S IN THE LOW DESERTS, 70S TO LOW 80S IN THE MOUNTAINS, MID
80S TO LOW 90S FOR THE WESTERN VALLEYS, AND MID 70S ALONG THE
COAST.
THE WARMING TREND WILL CONTINUE INTO WED UNDER A WEAK HIGH
PRESSURE RIDGE BETWEEN THE UPPER LOW TO THE SOUTHWEST AND ANOTHER
MORE INTENSE LOW PRESSURE SYSTEM MOVING INLAND OVER THE PAC
NORTHWEST. BY TUESDAY, DAYTIME TEMPERATURES WILL BE UP TO 10
DEGREES ABOVE SEASONAL AVERAGES INLAND WEST OF THE MTNS.
TEMPERATURES WILL LOWER FOR THE SECOND HALF OF THE WEEK AS THE
UPPER LOW MOVES CLOSER TO SOCAL AND ANOTHER LOW/TROUGH DEVELOPS
OFF THE WEST COAST. TEMPERATURES WILL LOWER TO NEAR OR A LITTLE
BELOW SEASONAL AVERAGES BY FRIDAY...EXCEPT IN THE COASTAL AREAS
AND WESTERN VALLEYS. TEMPS WILL SEE ONLY MINOR VARIATIONS FROM
FRI THROUGH NEXT WEEKEND.
THE UPPER LOW TO OUR SOUTHWEST WILL LIKELY HELP TO ADVECT MOISTURE
FROM TROPICAL STORM MARIO INTO SOCAL AS EARLY AS TUESDAY. WHILE AN
INCREASE IN MID AND HIGH CLOUDS IS EXPECTED ON TUESDAY, PRECIP IS
UNLIKELY DUE TO A LACK OF FORCING TO PRODUCE DEEP CONVECTION. BY
WEDNESDAY, MOISTURE AND INSTABILITY WILL INCREASE. THESE CONDITIONS
WILL LIKELY CONTINUE INTO NEXT WEEKEND, BRINGING CHANCES FOR
SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE REGION. THE BEST
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL BE IN THE MOUNTAINS
AND DESERTS (30-60%) BUT SHOWERS/THUNDERSTORMS CANNOT BE RULED
OUT WEST OF THE MOUNTAINS. FOR AREAS WEST OF THE MOUNTAINS,
GUIDANCE IS CURRENTLY SHOWING THURSDAY AND FRIDAY AS HAVING THE
HIGHEST CHANCES (20-35%) WITH LESSER CHANCES WEDNESDAY AND
SATURDAY (15-20%). THERE IS STILL UNCERTAINTY SURROUNDING THE
DETAILS BUT THE MAJORITY OF ENSEMBLE MEMBERS ACROSS MODEL
PLATFORMS FAVOR A DRY SOLUTION FOR SOCAL THROUGH TUESDAY THEN A
MAJORITY FAVOR A WET SOLUTION FOR WED THROUGH SATURDAY. CONDITIONS
COULD BEGIN TO DRY OUT NEXT SUNDAY AS WE LOSE ACCESS TO THE
MOISTURE FROM THE SOUTH, BUT FOR NOW A CHANCE OF SHOWERS AND
THUNDERSTORMS REMAINS IN THE MOUNTAINS INTO SUNDAY AFTERNOON.
AVIATION
150945Z...COAST/WESTERN VALLEYS...LOW CLOUDS BASED 1000-1500 FEET
MSL, TOPS TO 1900 FEET AND VIS 2-5SM OVER HIGHER COASTAL TERRAIN
WILL CONTINUE THIS MORNING. CLEARING TO THE COASTLINE WILL OCCUR 16-
18Z, BUT WITH PATCHY LOW CLOUDS LINGERING ALONG THE IMMEDIATE COAST
THEREAFTER. LOW CLOUDS TO BECOME LOWER, PATCHIER AND LESS UNIFORM IN
COVERAGE TONIGHT AFTER 03Z. CIGS SHOULD BE 700-1000 FEET, VIS 3-5SM
CONFINED TO COASTAL AREAS.
INLAND VALLEYS/MOUNTAINS/DESERTS...MOSTLY CLEAR AND VFR CONDITIONS
TODAY AND TONIGHT. SOME INCREASE IN CLOUDS AOA 10000 FEET TONIGHT.
MARINE
THERE IS A SLIGHT CHANCE OF THUNDERSTORMS WEDNESDAY THROUGH FRIDAY.
ANY STORMS THAT DEVELOP COULD BRIEFLY PRODUCE GUSTY WINDS, CHOPPY
SEAS, AND LIGHTNING. OTHERWISE, NO HAZARDOUS MARINE CONDITIONS ARE
EXPECTED.
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...MM
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