019
FXUS66 KSGX 201004
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
304 AM PDT MON OCT 20 2025
SYNOPSIS
HIGH PRESSURE WILL CONTINUE ABOVE AVERAGE HIGH TEMPERATURES FOR
INLAND AREAS THROUGH TUESDAY WHILE WEAK ONSHORE FLOW BEGINS TO
SPREAD COOLING INTO COASTAL AREAS WITH A RETURN AND SLOW DEEPENING
OF A SHALLOW MARINE LAYER. A LOW PRESSURE SYSTEM FROM THE
SOUTHWEST WILL MOVE INLAND THROUGH SOUTHERN CALIFORNIA ON TUESDAY
NIGHT AND WEDNESDAY WITH WEDNESDAY HIGH TEMPERATURES AS MUCH AS
12 TO 18 DEGREES COOLER FOR THE MOUNTAINS AND INLAND VALLEYS AND
AS MUCH AS 5 TO 10 DEGREES BELOW AVERAGE FOR THE MOUNTAINS AND
VALLEYS. HIGH PRESSURE WILL BRING WARMING FOR THURSDAY AND FRIDAY
WITH FRIDAY HIGH TEMPERATURES AROUND 5 DEGREES ABOVE AVERAGE FOR
INLAND AREAS. A LOW PRESSURE SYSTEM MOVING INLAND TO THE NORTH
WILL BRING COOLING FOR NEXT WEEKEND.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
SHORT TERM (TODAY THROUGH WEDNESDAY)
HIGH PRESSURE ALOFT OVER CALIFORNIA WILL KEEP INLAND AREAS WARMER
THROUGH TUESDAY WITH HIGH TEMPERATURES AROUND 5 DEGREES ABOVE
AVERAGE. A RETURN OF WEAK ONSHORE FLOW FOR COASTAL AREAS WILL
BEGIN TO SPREAD COOLING INLAND FOR TODAY AND TUESDAY. THERE WILL
BE A RETURN OF NIGHT AND MORNING COASTAL LOW CLOUDS WITH A SHALLOW
MARINE LAYER BEGINNING TO SLOWLY DEEPEN FOR TONIGHT INTO TUESDAY
MORNING.
A LOW PRESSURE SYSTEM FROM THE SOUTHWEST WILL MOVE INLAND THROUGH
SOUTHERN CALIFORNIA ON TUESDAY NIGHT AND WEDNESDAY. THIS WILL
STRENGTHEN ONSHORE FLOW AND SPREAD COOLING INLAND. HIGH
TEMPERATURES ON WEDNESDAY FOR THE MOUNTAINS AND DESERTS WILL COOL
AS MUCH AS 12 TO 18 DEGREES FROM THOSE ON TUESDAY. WEDNESDAY HIGH
TEMPERATURES WILL BE AS MUCH AS 5 TO 10 DEGREES BELOW AVERAGE FOR
THE MOUNTAINS AND VALLEYS. WEDNESDAY HIGH TEMPERATURES 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 FOR TUESDAY NIGHT AND WEDNESDAY WITH
COASTAL LOW CLOUDS COVERING MUCH OF THE COAST AND VALLEYS FOR
WEDNESDAY MORNING. THIS LOW PRESSURE SYSTEM HAS LIMITED MOISTURE
WITH NBM CHANCES FOR MEASURABLE PRECIPITATION OF 5 PERCENT OR
LESS.
LONG TERM (THURSDAY THROUGH SUNDAY)
HIGH PRESSURE MOVING INLAND ACROSS CALIFORNIA WILL BRING WARMING
FOR THURSDAY AND FRIDAY WITH HIGH TEMPERATURES ON THURSDAY WARMING
AS MUCH AS 10 DEGREES FOR THE MOUNTAINS AND INLAND VALLEYS WITH
ADDITIONAL WARMING FOR MOST AREAS OF ANOTHER FEW TO 5 DEGREES ON
FRIDAY. WITH THE WARMING, FRIDAY HIGH TEMPERATURES WILL BE AROUND
5 DEGREES ABOVE AVERAGE FOR INLAND AREAS. FRIDAY HIGH
TEMPERATURES WILL RANGE FROM THE LOWER 70S NEAR THE COAST TO THE
LOWER TO MID 80S FOR THE INLAND EMPIRE WITH THE LOWER 90S FOR THE
LOWER DESERTS.
FOR NEXT WEEKEND, A LOW PRESSURE SYSTEM MOVING INLAND TO THE
NORTH WILL STRENGTHEN THE ONSHORE FLOW ACROSS SOUTHERN
CALIFORNIA. THIS WILL 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.
AVIATION
200930Z....COAST...FEW-SCT LOW CLOUDS AND FOG THROUGH 15Z. LOW
CONFIDENCE, BUT IF ANY CIGS OCCUR, BASES WOULD BE 400-500 FEET MSL
AND VIS 0-4SM. GREATER CONFIDENCE IN AREAS OF LOW CLOUDS AND FOG
AFTER 06Z TONIGHT, INCREASING IN COVERAGE INTO TUESDAY. CIGS/VIS
WOULD BE SLIGHTLY HIGHER.
VALLEYS/MOUNTAINS/DESERTS...CLEAR AND VFR CONDITIONS CONTINUE TODAY
AND TONIGHT.
MARINE
PATCHY FOG TO REDUCE VISIBILITY THIS 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...17
AVIATION/MARINE...MM
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