Spring Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

722
FXUS66 KSGX 132113
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
113 PM PST Sat Dec 13 2025

.SYNOPSIS...
High pressure will continue to dominate the region over the next
week, keeping high temperatures well above normal with minor day
to day changes. The marine layer remains very shallow, leading to
low clouds and fog near the coast, where the fog may be locally
dense over the next couple of nights/mornings.

&&

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

Today into Sunday...

Satellite imagery and 500mb analysis reveal the upper level ridge
which has been in control across the region extending from Baja
northward into the western Great Basin, with a shortwave off the
north-central California Coast. The strong and shallow subsidence
inversion resulting from the presence of the ridge is keeping the
marine layer very low, with fog from this morning finally clearing
across most of the coastal areas this afternoon. As the shortwaves
continues to round the northern side of the ridge, the ridge will
weaken some and its axis will nudge eastward, leading to a slightly
weaker inversion. While a similar marine layer presence is expected
tonight compared to this morning, bases may be a touch higher with
locally dense fog expected for higher coastal terrain through
portions of the western inland valleys. Temperatures continue to
stay above normal under the ridge, with very mild nighttime
temperatures for elevations within the inversion (generally 2000-
4000ft).

Monday and Tuesday...

The shortwave trough will tighten the surface offshore gradient some
for Monday afternoon, with weak offshore winds expected, primarily
restricted to the main mountain passes. Strongest wind gusts of 25-
30 mph possible in these areas. The weak offshore flow will also
help clear the marine layer out earlier Monday morning and allow
temperatures to warm back up to 15-20 degrees above normal. Onshore
flow resumes Tuesday but a meager marine layer Tuesday morning keeps
afternoon temperatures similarly above normal as Monday`s.

Wednesday through Late Week...

Ensemble clusters continue to favor a generally zonal upper level
flow with broad ridging in place through some clusters feature
slightly stronger ridging. Regardless, this pattern will keep
temperatures slightly above normal, albeit less anomalous than
Monday/Tuesday...with no precipitation chances in sight. Higher
elevations, particularly the High Deserts could see elevated
onshore flow if the ridging isn`t as strong.

&&

.AVIATION...
132100Z...Coast/Valleys...Low clouds and fog have finally moved off
of the coastal sites with some scattered to few low clouds lingering
around 800-900 ft MSL. Low clouds and fog are expected to return
this evening after 02-03Z along the coast and up to 15 SM inland
with low cloud bases around 100-500 ft MSL and visibilities 4 SM or
less.

Mountains/Deserts...Clear skies and VFR conditions expected through
the TAF period.

&&

.MARINE...
Much patchier and not nearly as dense fog is expected to develop
this evening out over the local waters and last into Sunday morning.
Otherwise, no hazardous marine conditions are expected through
Thursday.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...Munyan
AVIATION/MARINE...Villafane