937
FXUS66 KSGX 220354
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
854 PM PDT TUE OCT 21 2025
SYNOPSIS
SCATTERED SPRINKLES AND LIGHT SHOWERS TONIGHT. THE MARINE LAYER
WILL DEEPEN AND SPREAD FAR INLAND TONIGHT, BRINGING PATCHY DRIZZLE
WEDNESDAY MORNING. COOLER WEDNESDAY WITH STRONGER SOUTHWEST TO
WEST WINDS IN THE MOUNTAINS AND DESERTS. WARMER THURSDAY AND
FRIDAY WITH WEAK OFFSHORE FLOW. A LOW PRESSURE SYSTEM MOVING
INLAND TO THE NORTH WILL BRING COOLER AND BREEZY CONDITIONS FOR
THE WEEKEND, FOLLOWED BY WARMING AND ANOTHER ROUND OF OFFSHORE
FLOW EARLY NEXT WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
EVENING UPDATE...
THE UPPER LEVEL LOW REMAINS OFF THE COAST OF SO CAL THIS EVENING.
A BAND OF LIGHT SHOWERS AND EVEN A RECENTLY OBSERVED LIGHTNING
STRIKE NEAR LONG BEACH HAS DEVELOPED ON THE NORTHEAST SIDE OF THE
LOW, THOUGH DUE TO A VERY DRY SUBCLOUD LAYER ANY PRECIPITATION
ACCUMULATION HAS BEEN LIMITED TO A COUPLE HUNDREDTHS OF AN INCH.
THE LOW WILL LIFT NORTH AND SLIGHTLY EASTWARD OVERNIGHT, WITH ANY
LINGERING MID- LEVEL INSTABILITY AND BETTER DYNAMICS SHIFTING
NORTH OF OUR AREA. THE 00Z KNKX SOUNDING SHOWS THE MARINE
INVERSION BASED NEAR 1200 FT MSL. THE MARINE LAYER WILL DEEPEN
OVERNIGHT AS THE UPPER LOW MOVES CLOSER, BUT NOT CONVINCED IT WILL
DEEPEN ENOUGH TO PRODUCE ANY DRIZZLE TONIGHT.
THE LOW MOVES EAST ACROSS THE REGION DURING THE DAY WEDNESDAY.
THIS WILL BRING SIGNIFICANT COOLING AND GUSTY SOUTHWEST TO WEST
WINDS IN THE MOUNTAINS AND DESERTS. HIGHS WEDNESDAY WILL BE AS
MUCH AS 10-15 DEGREES LOWER THAN TODAY ACROSS THE MOUNTAINS,
VALLEYS, AND HIGH DESERT, AND AROUND 5 DEGREES LOWER FOR THE LOW
DESERTS AND COASTAL AREAS. WINDS WILL BEGIN TO STRENGTHEN
WEDNESDAY MORNING ACROSS THE MOUNTAIN RIDGES AND UPPER DESERT
MOUNTAIN SLOPES, SPREADING INTO THE PASSES AND DESERTS WEDNESDAY
AFTERNOON AND EVENING WITH PEAK GUSTS OF 35-45 MPH, LOCALLY UP TO
55 MPH BELOW THE PASSES. THE LOW BEGINS TO MOVE OFF TO THE EAST
WEDNESDAY NIGHT INTO THURSDAY MORNING, AND WINDS WILL BEGIN TO
WEAKEN DURING THAT TIME. THE MARINE LAYER WILL DEEPEN FURTHER
WEDNESDAY NIGHT, WITH PERHAPS A BETTER CHANCE OF DRIZZLE WEST OF
THE MOUNTAINS.
WEAK TROUGHING LINGERS ACROSS THE REGION ON THURSDAY, AND WHILE
MID-LEVEL WINDS TURN NORTHERLY, WEAK ONSHORE PRESSURE GRADIENTS
REMAIN THROUGH THE DAY, TURNING VERY WEAKLY OFFSHORE TO THE NORTH
THURSDAY NIGHT INTO FRIDAY MORNING. OVERALL THIS WILL LEAD TO
AROUND 5 DEGREES OF WARMING THURSDAY WITH HIGHS GENERALLY A FEW
DEGREES BELOW NORMAL.
PREVIOUS DISCUSSION...
RIDGING AMPLIFIES INTO FRIDAY, AND THE MINI WARM-UP WILL PEAK
FRIDAY AFTERNOON WITH HIGH TEMPERATURES AROUND 5 DEGREES ABOVE
AVERAGE AWAY FROM THE IMMEDIATE COAST. THE RIDGE WILL START TO
FLATTEN AND MOVE OFF TO THE EAST SATURDAY AS A LARGE TROUGH DROPS
FROM THE NORTHWEST. MODEL AGREEMENT IS PRETTY GOOD, WITH THIS
REMAINING FAIRLY WELL TO OUR NORTH, BUT THIS WILL LEAD TO COOLING
TEMPERATURES THIS WEEKEND AND LOCALLY BREEZY WINDS (MOST LIKELY
LEE MOUNTAIN FOOTHILLS AND DESERTS AGAIN), AS WELL AS THE MARINE
LAYER DEEPENING AGAIN. A FEW GLOBAL ENSEMBLE MEMBERS STILL HAVE
LIGHT SHOWERS WEST OF THE MOUNTAINS, BUT THE LARGE MAJORITY ARE
DRY.
SOME UNCERTAINTY WITH RESPECT TO THE PATTERN NEXT WEEK, BUT SOME
FORM OF RIDGING IS MORE LIKELY, WHICH WILL BRING WARMING
TEMPERATURES AGAIN, POSSIBLY TO WELL ABOVE AVERAGE.
AVIATION
220330Z...COAST/VALLEYS...LOW CLOUDS BASED 1000-1500 FT MSL
CURRENTLY DEVELOPING ALONG THE SAN DIEGO COUNTY COASTLINE. COVERAGE
EXPANDING TO INCLUDE MOST OF THE COASTAL BASIN OVERNIGHT WITH BASES
CONTINUALLY RISING TO ABOVE 2000 FT MSL AFTER 12Z WED. SCATTER OUT
17-19Z. LOW CLOUDS BASED ABOVE 2000 FT MSL RETURN EARLY (00-03Z THU)
FOR SAN DIEGO COUNTY AND ALONG COASTAL SLOPES OF THE MTNS. SLOWLY
FILLING TO COVER THE REST OF THE COASTAL BASIN OVERNIGHT.
OTHERWISE...SCT-BKN CLOUDS 12000-22000 FEET MSL WITH VFR CONDITIONS
THROUGH THE TAF PERIOD. STRENGTHENING WEST WINDS THROUGH WED
MORNING. GUSTS 30-40 KTS ALONG AND DOWNWIND OF EASTERN FACING MTN
SLOPES AFTER 18Z. GUSTS TO 50 KTS THROUGH THE MOST WIND-PRONE PASSES.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH SUNDAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...WIND ADVISORY FROM 10 AM WEDNESDAY TO MIDNIGHT PDT WEDNESDAY
NIGHT FOR SAN DIEGO COUNTY DESERTS-SAN GORGONIO PASS NEAR
BANNING.
PZ...NONE.
PUBLIC...SS/CSP
AVIATION/MARINE...KW
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