Alta Loma, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

659
FXUS66 KSGX 261959
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1259 PM PDT Tue May 26 2026

.SYNOPSIS...
The marine layer will remain around 5000 feet through Wednesday.
There could be some drizzle or light rain from this deep marine
layer at times, mainly late at night into the morning into
Thursday morning. High temperatures will lower several degrees for
Tuesday and Wednesday to as much as 20 to 25 degrees below
average for the mountains on Wednesday. Southwest to west winds in
the mountains and deserts will strengthen for this afternoon
through Wednesday night, with gusts of 40 to 50 mph with isolated
gusts to 70 mph through the passes. There will be warming for
Friday through next weekend with the marine layer becoming
shallower.

&&

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

This afternoon...The marine layer is about 5000 ft deep with
widespread low clouds west of the mtns, although there are breaks
in the cloud layer with some reverse clearing at the coast.
Temperatures are generally lower than at this time yesterday, with
some locations in the mtns and high deserts as much as 15-20
degrees cooler.

The low pressure system with a closed upper low over NorCal will
move south through Thursday before turning east on Fri, moving
into the Rockies by Saturday. High temperatures today will be as
much as 10 to 15 degrees lower than yesterday for some inland
areas and as much as another 5 to 10 degrees cooler on Wednesday
for the mountains and deserts. High temperatures in the mountains
on Wednesday will be as much as 20 to 25 degrees below average.
High temperatures on Wednesday will be mostly in the 60s for the
coast and valleys and in the upper 70s to mid 80s for the lower
deserts, with the mountains mostly in the 40s and 50s and the
high desert in the 60s.

The marine layer will remain about 5000 ft deep (give-or-take)
through Thursday. The deep marine layer and thick saturated layer
could bring patchy drizzle to areas west of the mtns tonight/Wed
morning and again Wed night into Thu morning, although measurable
precipitation is not very likely.

This low pressure system will also bring stronger onshore flow
resulting in southwest to west winds gusting 40 to 50 mph at times
in the mtns and deserts. Gusts of up to 65 mph could also occur
in the northern Coachella Valley below the San Gorgonio Pass. The
strong winds will likely last from today through Wed night before
weakening on Thu.

A warming trend begins on Friday as the low pressure system begins
to move east but daytime temperatures will likely remain mostly below
normal through Sat. The warming continues into early next week.
Forecast details are uncertain for this period due to the spread
among model solutions but next Tue looks like it will be the
warmest day, with temperatures near or several degrees above
normal. SoCal will remain under weak troughing aloft with (weaker)
onshore flow at the surface which will likely moderate
temperatures west of the mtns.

&&

.AVIATION...
261800Z...Coast/Valleys/Foothills...BKN-OVC low clouds based 3500-
4500 ft MSL and FEW-SCT low clouds 2500-3500 ft MSL are covering the
entire coastal basin. The BKN cloud deck will become SCT in parts of
the Inland Empire and coastal areas from 20-02z this afternoon.
Otherwise, cigs will struggle to scatter elsewhere. Any remaining
clear patches should fill back in around 00-04z Wed. Bases will
generally be 3000-4000 ft MSL Tuesday night with periods of cigs
down to 2500 ft MSL from 02-13z Wed. Patchy coastal -DZ from 09-15z.
Cigs lift mostly above 3500 ft MSL once again Wednesday morning,
though remaining BKN-OVC.

Higher Mountains/Deserts...Partly cloudy skies and VFR conditions
expected through the TAF period. Gusty west winds through the TAF
period, especially 22-10z this afternoon and night. Widespread gusts
30-40 kts with isolated gusts to 65 kts through the passes.

&&

.MARINE...
Winds and seas increase this afternoon and into early Wednesday,
generating hazardous conditions for small craft in the outer waters,
especially near San Clemente Island. For more details, see the Small
Craft Advisory product. Winds and seas decrease Wednesday night,
with no hazardous marine conditions are expected thereafter 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 until 5 AM PDT Thursday for Riverside County
     Mountains-San Diego County Deserts-San Diego County
     Mountains-San Gorgonio Pass near Banning.

     Wind Advisory until midnight PDT tonight for Apple and Lucerne
     Valleys.

PZ...Small Craft Advisory until 1 PM PDT Wednesday for Waters from
     San Mateo Point to the Mexican Border Extending 10 to 60 nm
     out including San Clemente Island.

&&

$$

PUBLIC...PG
AVIATION/MARINE...Westerink