Colton, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

098
FXUS66 KSGX 250340
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
840 PM PDT Thu Jul 24 2025

.SYNOPSIS...
Below average high temperatures will continue through the weekend.
Night and morning coastal low clouds and fog will reach into
portions of the valleys late each night. A warming trend will start
Sunday with highs warming to near or slightly above average by the
middle of next week. A minor influx of monsoonal moisture for the
latter half of next week will bring a slight (less than 15
percent) chance of afternoon showers and thunderstorms for the
mountains beginning on Wednesday.

&&

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

Evening update...
Marine layer low clouds have redeveloped and are pushing into the
coastal areas this evening. The 00Z KNKX sounding shows the marine
inversion based near 1400 ft MSL, down from 2000 ft this morning.
Slight deepening is expected overnight as the upper level low off
the west coast progresses eastward, with low clouds spreading into
the western valleys by Friday morning. Otherwise breezy west
winds through the passes and clear skies tonight. No changes to
the forecast this evening.

Previous discussion...
The marine layer is expected to stay 1500 to 2500 feet deep through
much of the forecast period, being on the deeper side over the
weekend and the shallower side next week. Low clouds and fog are
expected to reach into portions of the valleys each night and
morning, with more coverage when the marine layer is deeper and less
when it is shallower.

A low pressure system off the coast of central California will
linger offshore through Friday, before finally moving inland
Saturday. This will increase the onshore pressure gradient which
will result in an uptick in winds on desert mountain slopes and into
the deserts. Sea breeze winds each afternoon and evening will gust
to 20 to 30 mph with gusts to 35 to 45 mph in the northern Coachella
Valley below the San Gorgonio Pass.

Slight cooling trend expected through Saturday, with below average
temperatures prevailing. A warming trend will begin Sunday as high
pressure to the east strengthens. Monday through Wednesday, high
temperatures will warm to near or slightly above the seasonal
average. For Tuesday and Wednesday, NBM chances of the low desert
exceeding 110 degrees are 30 to 60 percent with a 15 to 30 percent
chance, locally up to 60 percent, of the Inland Empire reaching or
exceeding 100 degrees.

There could be some influx of monsoonal moisture for the latter half
of next week. NBM daily chances for measurable rainfall for Big Bear
increase to 9 percent on Wednesday and 13 percent on Thursday with
chances for one-half inch or more of rainfall less than 5 percent.

&&

.AVIATION...
250330Z....Coast/western Valleys...Low clouds based at 1000-1200
feet MSL will continue to develop along the coast, first in San
Diego County and later in Orange County, and eventually spread into
western valleys overnight. Local vis reduced 2-5SM inland. Scatter
out 16-17Z Friday. Low clouds based around 1500 feet to redevelop
after 01Z Friday evening and push farther inland Friday night.

Inland Valleys/Mountains/Deserts...Mostly clear and VFR conditions
through Friday.

&&

.MARINE...
Northwest wind gusts around 20 kts expected in the vicinity of San
Clemente Island during afternoons and evenings through Friday.
Otherwise, no hazardous marine conditions are expected through
Tuesday.

&&

.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...SS/CO
AVIATION/MARINE...MM