Chula Vista, California Weather Forecast Discussion

630
FXUS66 KSGX 242108
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
208 PM PDT Wed Sep 24 2025
.SYNOPSIS...
An area of low pressure off the Central Coast will move southward
over Southern California into the weekend. This will bring
slightly cooler weather along with elevated west winds and a
chance for thunderstorms across the mountains and deserts. The
windiest day looks to be on Thursday with the highest chance for
thunderstorms on Saturday. A large trough off the Pacific will
move into the West Coast by early next week, keeping temperatures
constant with drier weather over our region.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
A 578mb area of low pressure is currently off the Central Coast,
leading to showers across the San Joaquin Valley this afternoon.
Forecast models show this feature moving inland and southward into
the weekend. As it moves closer to our region on Thursday, the
pressure gradient will tighten, leading to increased SW/W winds
across the mountains and deserts. Most areas will see wind gusts
35-45 MPH, locally over 50 mph across passes. The forecast
remains on track for highest winds to be focused across San Diego
and Riverside Counties. This system will also bring cooler weather
with most areas cooling 5 to 10 degrees from what we are seeing
today. This cooling trend will continue into Friday and over the
weekend with highs near 5 to 10 degrees below normal with all
areas west of the mountains ranging from 70-85 degrees with 90s
and even some 80s expected in the lower deserts.
The low pressure system will move over SoCal later on Thursday
into Friday, which will help rapidly deepen the marine layer. This
will bring in clouds and patchy fog to all areas west of the
mountains. The moisture layer may become deep enough to support
some areas of drizzle closer to the coast by Friday morning as
well. Increasing instability is present in model guidance with
depictions near 200-500 J/kg and hi-res models showing increased
acidified over the mountains and deserts by Friday afternoon.
Light showers and a possible thunderstorm may occur with hourly
rain rates over 1/4". Otherwise, most areas will remain dry.
Instability will slightly increase by Saturday as the low slows
over the Colorado River Valley. The moisture will wrap around the
low from the NE, where heavier showers and storms will be expected
across the mountains and deserts. Some of these storms may make
it into the valleys west of the mountains (mainly areas east of
Interstates 15/215) late Saturday afternoon and evening. The low
is expected to weaken and move further east on Sunday, so a
lingering small chance of storms will continue across the RIV/SBD
mts. Other areas will remain dry with marine layer clouds nights
and mornings west of the mountains.
As move toward next week, model ensembles are in fair agreement of
a large trough of low pressure moving closer to the West Coast by
Monday through the middle of next week. The exact strength and
position of this low is still in question, but its prescience
will keep temperatures rather unchanged from the weekend with
highs slightly below normal. We should remain fairly dry, though a
small number of ensembles do show a chance for light precipiation.
&&
.AVIATION...
242030Z....Coasts/Valleys...Localized patchy low clouds currently at
San Diego County beaches. Otherwise, VFR through the evening with
low clouds returning to coastal areas 03-06Z Thursday. Better
coverage of low clouds expected with higher bases (1000-1500 ft MSL)
and extending 15-20 miles inland by 12Z Thu. 40% chance BKN cigs in
the western/southern Inland Empire after 11Z. Vis reductions
possible for elevated inland valleys (2-5 SM). Clearing to the
coastline by 17-19Z Thu.
Mountains/Deserts...SCT clouds 10000-15000 feet MSL over mountains
through the early evening. Otherwise, mostly clear and VFR
conditions through Thursday.
&&
.MARINE...
No hazardous marine conditions are expected through Sunday. However,
stronger northwest winds with gusts approaching 20 knots at times
near San Clemente Island are expected in the afternoons and evenings
today and Thursday.
&&
.BEACHES...
Long period southerly swell from Hurricane Narda will reach the
coastal waters this weekend. Swell of 5-6 feet with periods 14-15
seconds will produce high surf for southern facing beaches from late
Saturday through early next week. Elevated surf and strong rip
currents can be expected along the entire coastline. More details in
the coming days.
&&
.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...APR
AVIATION/MARINE...KW

NWS SGX Office Area Forecast Discussion