Spring Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

164
FXUS66 KSGX 170528
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1028 PM PDT Wed Sep 16 2026

.SYNOPSIS...
Below average temperatures will continue through Friday. Conditions
will warm over the weekend, with a brief cooling trend early in
the week. Conditions will warm for the middle of next week,
returning to around average by next Wednesday. Night and morning
low clouds and fog will reach well into the valley again tonight
into Thursday, becoming shallower over the weekend.

&&

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

...UPDATED AVIATION DISCUSSION...

The marine layer was around 3500 ft deep this morning, with low
clouds filling in the coastal basin. Visible satellite from this
morning even showed low clouds through the Cajon Pass. At 11 AM,
satellite was still showing patchy low clouds along the coast and
portions of the western valleys. The marine layer is expected to
stay a similar depth tonight, with similar inland extent expected.
The marine layer will become shallower for Friday into the weekend
with night and morning coastal low clouds not spreading inland past
the far western valleys.

Weak troughing will gradually move east into the Great Basin by this
weekend. That will result in below cooler conditions through
Thursday, with a gradual warming Friday through Sunday as weak
transient ridging builds over the West Coast. The warming will be
most noticeable for inland locations. Even with the warming
daytime highs, overnight lows will continue to cool off helping
overnight relief from the heat.

Another trough of low pressure is expected to move west across
Southern California Monday which will bring a few degrees of cooling
and deepen the marine layer again. By the middle of next week, there
starts to be some spread in the upper level pattern. NBM guidance
has an 8 degree difference between the 75th (warmer end of
solutions) and 25th (cooler end of solutions) percentile
temperatures for the inland valleys. The current forecast follows
the NBM which has temperatures within a few degrees of average for
most locations.

&&

.AVIATION...
170530Z...Coast/Valleys...Low clouds around 2600-3200 feet MSL will
continue to fill most if not all of the coastal basin by 12Z
Thursday. Bases will lift over 3000 feet MSL 14-18Z before
scattering out by 17-19Z. Low clouds based around 2000-3000 feet MSL
will return to KSAN and KCRQ rather early, by 23-02Z before
spreading north Thursday night.

Mountains/Deserts...Mostly clear and VFR conditions through
Thursday.

&&

.MARINE...
No hazardous marine conditions are expected through Monday.

&&

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