Modjeska, California Weather Forecast Discussion

302
FXUS66 KSGX 250407
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
907 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 stronger west winds and a
chance for thunderstorms across the mountains and deserts. The
windiest day will likely be Thursday, with the best chance for
thunderstorms on Saturday. A large trough over the eastern 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...
Temperatures this afternoon were mostly a few degrees lower than
yesterday except for the low deserts where temperatures were
mostly a few degrees higher. The marine layer is still very
shallow and low clouds are beginning to form in the coastal areas.
High-resolution models show the low clouds increasing in coverage
and spreading 10-15 miles inland by sunrise.
From previous discussion...
An area of low pressure is currently off the Central Coast,
with showers and thunderstorms continuing over the San Joaquin
Valley this evening. Forecast models show this feature moving
inland and southward through the weekend. As it moves closer to
our region on Thursday, the pressure gradient will tighten,
leading to stronger SW/W winds across the mountains and deserts.
Most areas will see wind gusts 35-45 MPH, locally over 50 mph
in favored locations. 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 through 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
activity 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 for
Monday through the middle of next week. The exact strength and
position of this low is still in question, but its presence 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...
2520345Z....Coasts/Valleys...Low clouds will continue to regather and
fill back into the valleys of Orange and San Diego counties with better
coverage and slightly higher bases of 1000-1500 ft MSL, which should
extend to around 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. These clouds will begin to fill back in
beginning around 01-03Z Sat, and then continue to expand eastward
and even into portions of the Inland Empire after that time.
Mountains/Deserts...FEW-SCT clouds 10000-15000 feet MSL will develop
over mountains through the early evening. Otherwise, mostly clear
and VFR conditions through Thursday evening.
&&
.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 afternoon and evening
tomorrow.
&&
.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...PG
AVIATION/MARINE...Stewey

NWS SGX Office Area Forecast Discussion