652
FXUS66 KSGX 210354
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
854 PM PDT MON OCT 20 2025
SYNOPSIS
ABOVE AVERAGE HIGH TEMPERATURES WILL CONTINUE FOR INLAND AREAS
THROUGH TUESDAY WHILE WEAK ONSHORE FLOW BEGINS TO SPREAD COOLING
INTO COASTAL AREAS AS A SHALLOW MARINE LAYER SLOWLY DEEPENS. MUCH
COOLER ON WEDNESDAY WITH THE MARINE LAYER DEEPENING FURTHER.
WARMER AGAIN ON THURSDAY AND FRIDAY, WITH FRIDAY HIGH TEMPERATURES
AROUND 5 DEGREES ABOVE AVERAGE FOR INLAND AREAS. COOLER AGAIN WITH
STRONGER ONSHORE FLOW AND A DEEPER MARINE LAYER FOR NEXT WEEKEND.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
HIGHS TUESDAY FOR INLAND AREAS WILL CONTINUE TO WARM ANOTHER FEW
DEGREES, WHILE COASTAL LOCATIONS BEGIN TO COOL WITH THE INCREASE IN
ONSHORE FLOW. A FEW PATCHES OF LOW CLOUDS HAVE DEVELOPED OVER THE
OCEAN AS OF 8:30 PM. PATCHES OF LOW CLOUDS AND FOG ARE EXPECTED TO
MAKE IT TO COASTAL AREAS LATER TONIGHT INTO EARLY TUESDAY
MORNING. AREAS OF FOG WITH VISIBILITY 1 MILE OR LESS IS POSSIBLE
AND MOST LIKELY TO OCCUR NEAR HIGHER COASTAL TERRAIN. LOW CLOUDS
MAY LINGER ALONG THE IMMEDIATE COAST INTO TUESDAY AFTERNOON.
FROM PREVIOUS DISCUSSION ISSUED AT 2 PM OCTOBER 20...
THE CLOSED UPPER LOW TO THE SOUTHWEST WILL MOVE INLAND OVER SOCAL
TUE NIGHT/WED. THIS WILL BRING SIGNIFICANT COOLING, STRONGER ONSHORE
FLOW AND A DEEPENING MARINE LAYER FOR WEDNESDAY. WED HIGH TEMPS WILL
BE AS MUCH AS 12 TO 18 DEGREES COOLER THAN TUE IN THE MTNS AND
DESERTS, AND ABOUT 5 TO 10 DEGREES BELOW SEASONAL AVERAGES FOR THE
MOUNTAINS AND VALLEYS. DAYTIME HIGH TEMPS WILL RANGE FROM THE MID TO
UPPER 60S NEAR THE COAST TO THE UPPER 60S TO MID 70S FOR THE INLAND
EMPIRE WITH THE LOWER TO MID 80S FOR THE LOWER DESERTS.
THE MARINE LAYER WILL DEEPEN SIGNIFICANTLY, ENABLING LOW CLOUDS TO
COVER MOST OF THE REGION WEST OF THE MTNS WED MORNING.
PRECIPITATION IS UNLIKELY WITH THIS SYSTEM BUT MORNING DRIZZLE FROM
THE DEEPENING MARINE LAYER LOW CLOUDS CAN'T BE RULED OUT.
FOR THU AND FRI...AS THE UPPER LOW MOVES EAST INTO THE ROCKIES, HIGH
PRESSURE RIDGING WILL MOVE IN FROM THE WEST. THIS WILL BRING WARMING
FOR THURSDAY AND FRIDAY, WITH HIGH TEMPERATURES ON THURSDAY RISING
BY AS MUCH AS 10 DEGREES IN THE MOUNTAINS AND INLAND VALLEYS.
ADDITIONAL WARMING OF ANOTHER 2 TO 5 DEGREES FOR MOST AREAS ON
FRIDAY. FRIDAY HIGH TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE
AVERAGE FOR INLAND AREAS AND WILL RANGE FROM THE LOWER 70S NEAR THE
COAST TO THE LOWER TO MID 80S FOR THE INLAND EMPIRE, AND THE LOWER
90S FOR THE LOWER DESERTS. THE MARINE LAYER WILL ALSO BECOME
SHALLOWER, WITH LOW CLOUDS RETREATING TO THE COASTAL AREAS ONCE
AGAIN.
FOR NEXT WEEKEND, A LOW PRESSURE SYSTEM MOVING INLAND TO THE NORTH
WILL STRENGTHEN THE ONSHORE FLOW ACROSS SOUTHERN CALIFORNIA. THIS
WILL AGAIN SPREAD COOLING INLAND, WITH HIGH TEMPERATURES NEXT SUNDAY
A FEW TO AROUND 5 DEGREES BELOW AVERAGE. HIGH TEMPERATURES FOR NEXT
SUNDAY WILL RANGE FROM AROUND 70 NEAR THE COAST TO THE LOWER TO MID
70S FOR THE INLAND EMPIRE WITH THE MID 80S FOR THE LOWER DESERTS.
THE MARINE LAYER WILL AGAIN DEEPEN ALLOWING LOW CLOUDS TO SPREAD
INTO THE INLAND VALLEYS AND FOOTHILLS.
AVIATION
210300Z....COAST/VALLEYS...AREAS OF LOW CLOUDS AND FOG BASED 300-600
FT MSL MOVE INTO COASTAL AREAS AFTER 06Z TONIGHT, BEGINNING ALONG
THE SAN DIEGO COUNTY COAST AND REACHING THE ORANGE COUNTY COAST
AROUND 09Z. VIS REDUCTIONS (2-5SM) LIKELY AT SEA LEVEL WITH VIS LESS
THAN 1 MILE POSSIBLE FOR ELEVATED COASTAL TERRAIN INCLUDING KCRQ. 5
TO 10 MILES OF INLAND EXTENT. CLOUDS AND ASSOCIATED VIS REDUCTIONS
SHOULD CLEAR FOR MOST AREAS AFTER 16-17Z TUESDAY, BUT PATCHY CLOUDS
MAY LINGER AT THE BEACHES AND OVER WATERS THROUGH THE AFTERNOON. LOW
CLOUDS PUSH INLAND AGAIN AFTER 03Z WEDNESDAY WITH HIGHER BASES AND
GREATER INLAND EXTENT.
MOUNTAINS/DESERTS...CLEAR SKIES WITH VFR CONDITIONS THROUGH THE TAF
PERIOD.
MARINE
PATCHY FOG TO REDUCE VISIBILITY (2-5SM) TUESDAY MORNING. OTHERWISE,
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH FRIDAY.
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...KW
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