900
FXUS66 KSGX 230955
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
255 AM PDT WED APR 23 2025
SYNOPSIS
A WEAK LOW PRESSURE SYSTEM MOVING INLAND THROUGH CALIFORNIA AND A
STRONGER LOW PRESSURE SYSTEM FOR FRIDAY NIGHT AND SATURDAY WILL
BRING A COOLING TREND THROUGH SATURDAY WITH SATURDAY HIGH
TEMPERATURES 10 TO 15 DEGREES BELOW AVERAGE FOR INLAND AREAS TO
AS MUCH AS 20 DEGREES BELOW AVERAGE FOR THE HIGHER ELEVATIONS OF
THE MOUNTAINS. THE MARINE LAYER WILL DEEPEN WITH NIGHT AND MORNING
COASTAL LOW CLOUDS AND FOG EXTENDING ONTO THE LOWER COASTAL SLOPES
OF THE MOUNTAINS FOR TODAY AND THURSDAY, THEN FARTHER ONTO THE
COASTAL MOUNTAIN SLOPES FOR FRIDAY AND SATURDAY. THERE WILL BE
STRONGER ONSHORE FLOW WITH STRONGER AND GUSTY SOUTHWEST TO WEST
WINDS FOR THE MOUNTAINS AND DESERTS EACH LATE AFTERNOON THROUGH
LATE EVENING THROUGH SATURDAY. THERE IS ALSO A SLIGHT CHANCE FOR
MOSTLY LIGHT SHOWERS FOR LATE FRIDAY NIGHT INTO SATURDAY EVENING.
THEN DRY WITH A WARMING TREND FOR SUNDAY THROUGH TUESDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
SHORT TERM (TODAY THROUGH FRIDAY)
A WEAK LOW PRESSURE SYSTEM WILL MOVE INLAND ACROSS CALIFORNIA
TODAY WITH A STRONGER LOW PRESSURE SYSTEM APPROACHING THE
CALIFORNIA COAST ON FRIDAY. COOLING WILL SPREAD INLAND THROUGH
FRIDAY WITH THE MARINE LAYER DEEPENING ONTO THE COASTAL MOUNTAIN
SLOPES. THERE WILL BE COOLING TODAY WITH NOT MUCH CHANGE ON
THURSDAY, THEN MORE COOLING FOR FRIDAY WITH FRIDAY HIGH
TEMPERATURES AS MUCH AS 8 TO 12 DEGREES BELOW AVERAGE FOR THE
MOUNTAINS AND INLAND VALLEYS.
THE MARINE LAYER HAS DEEPENED TO 3000 TO 3500 FEET WITH WIDESPREAD
LOW CLOUDS OVER THE COASTAL WATERS EXTENDING INLAND ACROSS ALL OF
THE VALLEYS AND INTO THE LOWER PORTIONS OF THE CAJON PASS. THE LOW
CLOUDS WILL ONCE AGAIN EXTEND INLAND AND ONTO THE LOWER COASTAL
SLOPES OF THE MOUNTAINS FOR TONIGHT INTO THURSDAY MORNING, THEN
ONTO MORE OF THE COASTAL SLOPES OF THE MOUNTAINS FOR THURSDAY
NIGHT INTO FRIDAY MORNING.
THERE WILL BE STRONGER ONSHORE FLOW WITH STRONGER AND GUSTY
SOUTHWEST TO WEST WINDS FOR THE MOUNTAINS AND DESERTS EACH LATE
AFTERNOON THROUGH LATE EVENING. THE STRONGER GUSTS ALONG AND BELOW
THE DESERT SLOPES OF THE MOUNTAINS WILL MOSTLY BE 35 TO 45 MPH
WITH GUSTS TO 45 TO 55 MPH IN THE NORTHERN COACHELLA VALLEY BELOW
THE SAN GORGONIO PASS.
LONG TERM (SATURDAY THROUGH TUESDAY)
SATURDAY IS EXPECTED TO BE THE COOLEST DAY WITH A LOW PRESSURE
SYSTEM MOVING INLAND ACROSS CALIFORNIA. HIGH TEMPERATURES WILL BE
MOSTLY 10 TO 15 DEGREES BELOW AVERAGE FOR THE MOUNTAINS, DESERTS,
AND VALLEYS TO LOCALLY 20 DEGREES BELOW AVERAGE FOR THE HIGHER
ELEVATIONS OF THE MOUNTAINS. A SLIGHT CHANCE OF SHOWERS HAS BEEN
ADDED TO THE FORECAST FOR LATE FRIDAY NIGHT INTO SATURDAY EVENING.
CHANCES FOR MEASURABLE PRECIPITATION IN THE FORECAST ARE CLOSER
TO THE ECMWF AND GFS MOS AND THE DEVELOPMENTAL NBM VERSION 5.0.
NBM STILL APPEARS TO BE TOO LOW WITH CHANCES FOR MEASURABLE
PRECIPITATION GIVEN THE PATTERN. IN ANY EVENT, ANY PRECIPITATION
WILL MOST LIKELY BE LIGHT.
DRY AND WARMER FOR SUNDAY THROUGH TUESDAY AS HIGH PRESSURE ALOFT
STRENGTHENS OFF THE CALIFORNIA COAST. HIGH TEMPERATURES ON SUNDAY
AS MUCH AS 8 TO 12 DEGREES BELOW AVERAGE FOR THE MOUNTAINS,
DESERTS, AND VALLEYS WILL WARM TO A FEW TO AROUND 5 DEGREES BELOW
AVERAGE ON MONDAY AND A FEW TO AROUND 5 DEGREES ABOVE AVERAGE ON
TUESDAY. TUESDAY HIGH TEMPERATURES WILL RANGE FROM THE MID TO
UPPER 60S NEAR THE COAST TO THE UPPER 70S TO LOWER 80S FOR THE
INLAND EMPIRE WITH THE LOWER TO MID 90S FOR THE LOWER DESERTS.
THE MARINE LAYER WILL BECOME SHALLOWER WITH NIGHT AND MORNING LOW
CLOUDS AND FOG NOT SPREADING AS FAR INLAND BY MONDAY AND TUESDAY.
AVIATION
230945Z....
COASTS/VALLEYS/COASTAL MOUNTAIN SLOPES...LOW CLOUDS
BASED AT 1700-2200 FEET MSL WITH TOPS TO 3000FT MSL HAVE SPREAD
EFFICIENTLY ACROSS THE COASTS AND VALLEYS THIS MORNING, FILLED IN
THROUGH THE COASTAL MOUNTAIN SLOPES. VIS LOCALLY REDUCED TO 4-6 SM
WITHIN INLAND VALLEYS, WITH OBSCURATION WHERE CLOUDS INTERSECT
HIGHER TERRAIN. THESE CLOUDS WILL SCATTER OUT FROM EAST TO WEST 16-
18Z AND MAY NOT CLEAR THROUGH THE BEACHES UNTIL ~19Z, ESPECIALLY IN
ORANGE COUNTY. CLOUDS SPREAD BACK ASHORE AFTER 00-03Z THURSDAY WITH
SIMILAR BASES AND INLAND EXTENT.
OTHERWISE...MOSTLY CLEAR THROUGH TUESDAY EVENING.
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...NONE.
PZ...NONE.
PUBLIC...17
AVIATION/MARINE...MUNYAN
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