328
FXUS66 KSGX 130516
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
916 PM PST Wed Nov 12 2025

.SYNOPSIS...
An incoming storm system will bring continued clouds, cooler
weather and penitential for widespread rainfall across all areas.
Another weather system may move over the area by early next week,
continuing the chance for rainfall and cooler weather.

&&

.PREV DISCUSSION...
A large trough of low pressure off the California coast will
continue to bring in mid-level clouds from southwest to northeast.
Height falls will continue throughout the day on Thursday, leading
to greater onshore flow and cooling across the region. Most areas
below 5000 and west of the mountains will cool into the 60s and
70s, while the lower deserts remain fairly warm in the upper 80s
for one more day. As the storm system moves closer, winds will
increase slightly across the mountain desert slopes into the
deserts with gusts mostly between 20-35 MPH, over 40 MPH in
mountain passes by Thursday afternoon and evening. Hi-res models
show increasing cloud cover with the potential for prefrontal
light showers and virga to move over the region by late Thursday
afternoon/night.

The trough will break away from the mean flow as the low deepens
offshore. This will form a cut off low west of the Southern
California coast. These systems are notorious for being quite
fickle and make for a difficult forecast. Forecasting the exact
movement of these weather systems is crucial in determining
precipitation occurrence and amounts. The system will be
associated with a frontal boundary that will move closer to the
area on Friday morning and afternoon. Hi-res models continue to
have a difficult time in pinpointing exactly how far south and
east the frontal boundary with associated rainfall progresses.
Confidence is highest for areas of Orange County, the western
Inland Empire and adjacent coastal slopes in receiving moderate
rainfall; confidence is lower to receive this rain for eastern and
southern areas, including San Diego. PWAT values increase over
1.25" with this frontal boundary, so locally heavy rainfall will
be possible to those who are impacted by it.

The low pressure system will deepen around 555 mb by Friday night
into Saturday, where its center will dip southward off the coast
somewhere parallel from Orange County to Ensenada. The
aforementioned frontal boundary will stall and eventually progress
over the region by Saturday. This will begin to bring in greater
amounts of moisture around the storm system from the subtropics,
where PWAT values remain elevated over 1" and IVT values peak in
weak to moderate intensity. There is increasing confidence that
Saturday will be the wettest day of this storm overall, where
widespread moderate to heavy rainfall is expected from the coast
to the deserts. While confidence remains low on exact rainfall
amounts due to the uncertainty of the storm`s exact path, please
be prepared for locally heavy rainfall and an increase threat for
flooding, including near former burn areas in the mountains. Since
this precipiation will be coming from the southeast or the south,
the coastal slopes of the mountains may receive locally 4-5" or
more of rainfall from Friday night into Saturday. There is also a
chance of some of embedded thunderstorms within this system as
instability will be elevated. The system will slowly exit the area
sometime on Sunday, though confidence in how much rainfall occurs
on this day is low, though most areas will see lighter precip.

Another weaker storm system has the potential to bring more wet
and cooler weather by early next week. Uncertainty remains high on
the path of this system and if it will even cross over our
region. Model ensembles provide greater confidence in showing an
overall cooler and breezier weather pattern by this time period. A
building ridge offshore makes things a bit more interesting by
the middle of next week...will the ridge be able to nudge its way
closer to our area and bring warmer/drier weather? Or will the
storm door remain open, leaving the chance for a more active
pattern and wetter weather? Only time will tell!

&&

.AVIATION...
130415Z...Coasts/Western Valleys...FEW clouds near 1000 ft MSL
offshore this evening, with some HZ; SCT-BKN mid and high clouds
between 10-20 kft overhead. Low clouds will struggle to build
through 10-12z. Thereafter, SCT-BKN bases broadly between 500-1000
ft to develop up to 10-15 miles inland. Patchy VIS reductions due to
BR/HZ of 0-4 SM along coastal mesas and inland valleys; For low
elevation coastal areas, VIS reductions mainly 4-6SM. Low clouds
scatter out to the coasts by 17-18z Thursday. Clouds will struggle
to form late Thursday once again, with FEW-SCT clouds based around
1000ft possible after 01z Friday.

Otherwise...VFR conditions will continue through Thursday evening.
BKN high clouds AOA 20 kft will gradually lower to around 15 kft by
Thursday.

&&

.MARINE...
A storm system will approach Friday and move through during the
weekend, boosting southerly wind gusts to near 20kts and creating
high seas.

Widespread rainfall is expected Friday through Sunday,
which may be moderate to heavy at times. There is a slight chance of
embedded thunderstorms Friday afternoon through Saturday.

&&

.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/17
AVIATION/MARINE...Westerink