Alta Loma, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

393
FXUS66 KSGX 260439
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
939 PM PDT Mon May 25 2026

.SYNOPSIS...
The marine layer will gradually deepen to around 5000 feet by
early Wednesday, with night and morning coastal low clouds
extending inland and onto the coastal slopes of the mountains.
High temperatures will lower by several degrees for Tuesday and
Wednesday reaching as much as 15 to 20 degrees below average in
the mountains on Wednesday. Southwest to west winds in the
mountains and deserts will strengthen for Tuesday afternoon
through Wednesday night, with gusts of 35 to 45 mph with isolated
gusts to 65 mph through the passes. There could be patchy drizzle
or light rain from the coast to the mountains during the nights
and mornings from late tonight into Thursday morning. There will
be warming for Friday through next weekend, with high temperatures
a few to around 5 degrees above average for next Sunday.

&&

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

New Aviation and Marine Discussion...

The marine layer is currently about 3500-4000 ft deep with an
inversion noticeably weaker than yesterday. This morning, the low
clouds had extended inland to the coastal mtn slopes but now most
areas are clearing except for the coastal areas of San Diego
County. The clearing is likely to continue for a few more hours
and the beaches of southern San Diego County could still see some
sunshine.

Weak, large-scale troughing over SoCal will be reinforced with
colder air as a low pressure system moves in from the northwest.
It will bring a cooling trend through Thursday. Wed and Thu are
likely to be the coolest days with daytime high temperatures 10-15
degrees below average in the inland valleys and deserts while the
mountains could be as much as 20 degrees below average. The
coastal areas will be near or a few degrees below average. This
system will also bring stronger onshore flow and a deepening
marine layer. Southwest to west winds will strengthen for Tue into
Thu with wind gusts of 35 to 45 mph in the mountains and deserts,
locally gusting to 65 mph in the favored locations. The marine
layer could deepen to about 5000 ft by Wed, and could produce patchy
drizzle or light rain west of the mtns each night and morning
into Thursday morning.

Toward the end of the week, temperatures rise as the low pressure
system moves east into the Rockies. Next Sun and Mon will likely
be the warmest days with temperatures generally a few degrees to
about 8 degrees above average. High temperatures for next Mon will
likely range from 70-75 near the coast to the low 90s for the
Inland Empire, with the lower deserts around 105. The marine layer
will also be shallower with night and morning low clouds not
spreading as far inland.


&&

.AVIATION...
260430Z...Coast/Valleys/Foothills...Low clouds with bases 2500-
3000ft MSL have filled in from the coast to the foothills of the San
Diego County mountains. Low clouds are beginning to develop in
Orange County and along the edges of the Inland Empire, and will
continue to increase and spread throughout the coastal basin over
the next few hours. Patchy drizzle will be possible around 13-18Z as
the marine layer deepens. Highest chances will be in areas near the
coast. Cloud bases will likely lift slightly after 17-19Z to 3000-
3500ft MSL and scatter in the Inland Empire.

Higher Mountains/Deserts...Mostly clear skies and VFR conditions
expected through the TAF period. West to southwest winds have
developed, creating stronger winds in the mountain passes and desert
slopes. These winds will increase after 18-19Z with gusts up to 35
to 45 mph with isolated gusts to 65 mph through the passes.

&&

.MARINE...
Winds and seas increase Tuesday afternoon and into early Wednesday,
generating hazardous conditions for small craft in the outer waters.
For more details, read the Small Craft Advisory. Otherwise, no
hazardous marine conditions are expected through Saturday.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 3 PM Tuesday to 5 AM PDT Thursday for
     Riverside County Mountains-San Diego County Deserts-San
     Diego County Mountains-San Gorgonio Pass near Banning.

     Wind Advisory from 3 PM Tuesday to midnight PDT Tuesday night
     for Apple and Lucerne Valleys.

PZ...Small Craft Advisory from 1 PM Tuesday to 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...Villafane