590
FXUS66 KSGX 200349
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
849 PM PDT SUN OCT 19 2025
SYNOPSIS
WEAK OFFSHORE FLOW WILL CONTINUE WITH EASTERLY BREEZES IN THE
FOOTHILLS AND COASTAL MTN SLOPES FOR MONDAY AND TUESDAY. NEAR TO
SLIGHTLY ABOVE AVERAGE TEMPERATURES EXPECTED THROUGH TUESDAY
BEFORE BELOW AVERAGE CONDITIONS RETURN FOR THE MIDDLE OF THE WEEK.
WARMER FOR FRIDAY THEN COOLER AGAIN FOR NEXT WEEKEND. PATCHES OF
MARINE LAYER LOW CLOUDS AND FOG THIS MORNING, WITH THE POTENTIAL
FOR AREAS OF DENSE FOG. LOW CLOUD COVERAGE WILL BECOME MORE
WIDESPREAD OVER THE NEXT SEVERAL DAYS. AREAS OF DRIZZLE POSSIBLE
WEDNESDAY FOR LOWER ELEVATIONS WEST OF THE MOUNTAINS.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
EVENING UPDATE
MOSTLY CLEAR SKIES ARE SEEN OVER THE REGION WITH PATCHY LOW CLOUDS
NEAR THE COAST. EXPECT LOW CLOUDS AND FOG TO BE INTERMITTENT.
LIGHT OFFSHORE FLOW OVERNIGHT WILL KEEP MOST LOW CLOUDS/FOG WITHIN
10 MILES OF THE COASTLINE WITH LOW CONFIDENCE ON FORMATION. THE
AREA OF LOW PRESSURE OFF THE COAST WILL MAKE ITS WAY OVER SOCAL BY
WEDNESDAY, LEADING TO COOLER WEATHER AND A DEEPER MARINE LAYER
WITH LOW CLOUDS EXTENDING FURTHER INTO THE WESTERN VALLEYS.
CHANCES FOR ANY PRECIPITATION CONTINUE TO LOOK MINIMAL BY NEXT
SUNDAY AS MOST MODELS PROJECT ACTIVITY FROM A PACIFIC STORM TO
STAY TO OUR NORTH.
PREVIOUS DISCUSSION (132 PM SUNDAY)
LOW CLOUDS AND FOG COULD MOVE ONSHORE TONIGHT BUT LIKELY WILL NOT
SPREAD INLAND BEYOND THE COASTAL AREAS. WEAK HIGH PRESSURE ALOFT
WILL PERSIST OVER THE REGION EARLY THIS WEEK BUT WILL SLOWLY SHIFT
NORTH AND EAST BY LATE TUESDAY AS A CLOSED UPPER LOW ABOUT 600
MILES SOUTHWEST OF SAN DIEGO MOVES TOWARD SOCAL. THE HIGH PRESSURE
WILL KEEP TEMPERATURES A LITTLE ABOVE SEASONAL AVERAGES THROUGH
TUESDAY. WEAK OFFSHORE PRESSURE GRADIENTS WILL PERSIST INTO
TUESDAY BUT OFFSHORE WINDS WILL BE RELATIVELY WEAK AND MOSTLY
RESTRICTED TO THE COASTAL SLOPES OF THE MOUNTAINS AND LOCALLY INTO
THE FOOTHILLS. THE OFFSHORE GRADIENTS WILL LIKELY LIMIT MARINE
LAYER LOW CLOUD AND FOG COVERAGE. ANY LOW CLOUDS AND FOG THAT DO
DEVELOP WILL MOST LIKELY OCCUR OVER THE COASTAL WATERS AND NEAR
THE COAST WITH AREAS OF DENSE FOG POSSIBLE.
THE CLOSED UPPER LOW TO THE SOUTHWEST WILL REACH SOCAL BY
WEDNESDAY, MOVING NORTHEAST AND ACCELERATING AS ANOTHER COLD
TROUGH BEGINS TO MOVE INLAND TO THE NORTH OVER WA/OR. THE PASSAGE
OF THIS LOW WILL BRING AN INCREASE IN CLOUD COVER AS THE MARINE
LAYER DEEPENS, AND COOLER, LOCALLY BREEZY CONDITIONS. ONSHORE
FLOW WILL STRENGTHEN AND LOCALLY GUSTY WINDS WILL DEVELOP IN THE
FAVORED LOCATIONS OF THE MTNS AND DESERTS. BY WEDNESDAY, HIGH
TEMPERATURES FOR INLAND LOCATIONS ARE EXPECTED TO BE 7 TO 12
DEGREES BELOW SEASONAL AVERAGES, WITH SOME MOUNTAIN LOCATIONS
SEEING HIGHS 15 TO 20 DEGREES BELOW AVERAGE. RAIN CHANCES
ASSOCIATED WITH THIS SYSTEM CONTINUE TO LOOK MARGINAL AS MOST OF
THE AVAILABLE MOISTURE WILL BE CONFINED TO THE MARINE LAYER.
CHANCES OF MEASURABLE RAINFALL OCCURRING REMAIN LESS THAN 10
PERCENT, WITH THE BEST CHANCES FOR ANY ACCUMULATING RAIN ON THE
COASTAL MOUNTAIN SLOPES. AREAS OF PATCHY DRIZZLE ARE POSSIBLE WEST
OF THE MOUNTAINS ON WEDNESDAY, ESPECIALLY WITH THE INCREASE IN
ONSHORE FLOW AND RAPID DEEPENING OF THE MARINE LAYER.
AS THE LOW MOVES EAST ON THURSDAY...A WEAK, TRANSIENT RIDGE WILL MOVE
IN FROM THE WEST. THIS RIDGE WILL BRING A BRIEF PERIOD OF WARMING,
WEAK OFFSHORE FLOW, AND A SHALLOWER MARINE LAYER FOR FRIDAY.
MARINE LAYER LOW CLOUDS WILL BE REDUCED AND DAYTIME HIGH
TEMPERATURES WILL BE NEAR OR A LITTLE ABOVE SEASONAL AVERAGES.
FOR NEXT WEEKEND...A DEEP TROUGH OF LOW PRESSURE FROM THE GULF OF
ALASKA WILL MOVE INLAND OVER THE WESTERN US. CURRENTLY, MOST OF
THE ENSEMBLE MEMBERS KEEPS THE PARENT LOW OFF THE COAST OF THE
PACIFIC NORTHWEST THROUGH NEXT SATURDAY, WHICH WOULD KEEP US DRY
THROUGH THEN. BY NEXT SUNDAY, MOST ENSEMBLE GUIDANCE HAS THE
TROUGH MOVING INLAND, ALTHOUGH THERE REMAINS SOME DIFFERENCES IN
TIMING AND AMPLITUDE OF THE TROUGH. THERE IS FAIRLY GOOD CONSENSUS
THAT THE TRACK OF THE LOW WILL BE MORE INLAND AND WELL TO THE
NORTH, SETTING UP A PATTERN OF HIGH-ZONAL FLOW OVER CA. THIS
PATTERN AND A LACK OF DEEP-LAYER MOISTURE MAKES IT LESS FAVORABLE
FOR SIGNIFICANT PRECIPITATION TO OCCUR. THERE ARE STILL SOME
ENSEMBLE MEMBERS SHOWING THAT LIGHT RAIN IS POSSIBLE, BUT MORE
THAN LIKELY THE MAIN IMPACT FROM THIS SYSTEM FOR SOCAL WILL BE A
STRENGTHENING OF WESTERLY WINDS OVER THE MOUNTAINS AND INTO THE
DESERTS. THIS TROUGH WILL ALSO BRING A COOLING TREND WITH DAYTIME
HIGH TEMPERATURES ONCE AGAIN BELOW SEASONAL AVERAGES FOR NEXT
WEEKEND.
AVIATION
200330Z....COASTS...FEW PATCHY LOW CLOUDS BASED BELOW 500 FT MSL
OVER THE OCEAN. WHILE CONFIDENCE ON TIMING IS LOW, LOW CLOUDS AND
FOG BASED BELOW 500 FT MSL COULD START TO DEVELOP ALONG THE COAST
BETWEEN 07-09Z, STAYING MOSTLY WITHIN 5 MILES OF THE COAST. LOW
CONFIDENCE FOR PATCHY FG FOR AREAS FURTHER INLAND BUT WEST OF I-15/I-
405 AND VALLEYS BELOW 700 FT MSL. VIS REDUCTIONS BELOW 1SM POSSIBLE
FOR VALLEYS AND AREAS BELOW 500 MSL THROUGH 15Z MON. FG AND LOW
CLOUDS SCATTER OUT 15-16Z MONDAY. HIGHER CONFIDENCE FOR GREATER
COVERAGE FOG AND LOW CLOUDS LATE MON.
VALLEYS/MOUNTAINS/DESERTS...VFR CONDITIONS CONTINUE THROUGH
LATE MONDAY.
MARINE
PATCHY FOG WITH VISIBILITIES UNDER 1SM WILL BE POSSIBLE MONDAY
MORNING. OTHERWISE, NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED
THROUGH THURSDAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
UPDATE...APR
PUBLIC...PG
AVIATION/MARINE...WESTERINK
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page