205
FXUS66 KSGX 031642
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
942 AM PDT Wed Sep 3 2025

.SYNOPSIS...
Monsoonal moisture will remain in place through Thursday with
chances for afternoon and early evening thunderstorms for the
mountains, deserts, and inland valleys. Greater drying will occur
for Friday and Saturday with a slight chance of thunderstorms for
the mountains and deserts for Friday afternoon. The drying will
continue into early next week along with a cooling trend with high
temperatures for next Tuesday a few to around 5 degrees below
average. Night and morning coastal low clouds will gradually
return through the weekend and spread locally into the far western
valleys late each night for next week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Update: Low clouds have completely cleared out for all of the
coastal locations at this hour, with some CU beginning to develop
over the mountains. There will be a chance of a few thunderstorms
this afternoon for the mountains and deserts. There are no
significant changes to the overall forecast at this time.

(Previous discussion submitted at

.SHORT TERM (Today through Friday)...
Greater monsoonal moisture will remain in place through Thursday
followed by a drying trend into early next week. Chances for
showers and thunderstorms will persist for the mountains,
deserts, and inland valleys during the late morning through early
evening with the greater chances for today and Thursday. The
greatest HREF 90th percentile hourly rainfall for today is around
one-half inch and is around one inch on Thursday as there may be
some increase in lower level moisture into the lower deserts on
early Thursday.

High temperatures will slowly cool with around 5 degrees of
cooling through Friday. Friday high temperatures will be near
average at the coast to around 5 degrees below average for the
lower deserts with high temperatures ranging from the 70s near
the coast to the upper 80s to mid 90s for the Inland Empire with
the upper 90s to 102 for the lower deserts.

&&

.LONG TERM (Saturday through Tuesday)...
The drying will continue into early next week. NBM daily chances
for measurable rainfall in the mountains falls below 10 percent on
Saturday and below 5 percent for Sunday into next week. A large
closed low pressure system well off the West Coast will begin to
bring dry southwest to west flow across the area beginning on
Saturday. This will persist through at least the middle of next
week as that low pressure system moves slowly into the western
states on Tuesday and Wednesday.

With the drying, nights will be gradually cooler. While there is
an overall cooling trend in high temperatures for early next week,
there is greater spread in the NBM high temperature guidance on
when the greater cooling occurs due to differences in the timing
and strength of the low pressure system as it moves into the
western states. With the cooling, high temperatures on Tuesday
will be a few to around 5 degrees below average with high
temperatures on Tuesday ranging from the 70s near the coast to the
upper 80s to mid 90s for the Inland Empire with 100 to 104 for
the lower deserts. Night and morning low clouds will spread inland
across coastal areas and sometimes in the far western valleys
late each night.

&&

.AVIATION... 031515Z...Coast...Patchy and intermittent low clouds
currently along the southern half of the San Diego County coast with
CIGs 600-900 feet MSL. VFR with some high clouds above 10kft will
prevail today. Patchy low clouds with similar bases and coverage
along the San Diego coast develop tonight generally after 10Z
Thursday, with clearing likely by 16z.

Valleys/Mountains/Deserts...Mostly clear through 19Z and after 01Z.
Clouds building over mountains with bases 9000 feet MSL and a chance
of SHRA/TSRA 19-01Z. TSRA tops to 35000 feet. Gusty and erratic
winds, blowing dust with low visibility, and lightning will
accompany any TSRA, along with lower bases 6000-9000 feet MSL.
Mostly clear with VFR after 05z Thur.

&&

.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.

&&

$$

UPDATE...Stewey
PUBLIC...17
AVIATION/MARINE...Zuber/Villafane

NWS Tucson (SGX) Office