960
FXUS66 KSGX 071657
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
957 AM PDT Tue Oct 7 2025

.SYNOPSIS...
There will be weak offshore flow this morning with gusty easterly
winds to 25 mph in the mountains. Moisture from the remnants of
Hurricane Priscilla will spread into the southwest states
on Thursday with chances for showers and thunderstorms for
southwestern California for Thursday into Friday night. This will
be followed be followed by cooling and drying into early next
week with Monday high temperatures 5 to locally 10 degrees below
average for inland areas.

&&

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

.SHORT TERM (today through Wednesday)...The west edge of a broad
subtropical ridge over the southern U.S. is currently over the
area, and a weak low is spinning in the eastern Pacific off the
central CA coast. Increased stability from the ridge is visible in
the stronger inversion present on this morning`s sounding
(compared to yesterday), which is contributing to our widespread
cloud cover.

Marine layer low clouds are about as far inland as they were
yesterday morning, covering most of Orange County outside of the
Santa Ana mountain peaks, San Diego as far east as Ramona, and
nudging into the Inland Empire near Temecula/Murrieta on the south
side and Ontario/Riverside/Corona on the northwest side. This is
leading to some low visibility, foggy conditions along the eastern
edge of the clouds, with stations near/in Ramona and Fallbrook
reporting less than a mile visibility currently and more
widespread 1-4 mile visibility in areas like El Cajon and
Ontario. These will gradually clear from east to west into the
early afternoon, with completely clear conditions following inland
but some patchy cloudiness hanging on to the immediate coast
through the afternoon again, mostly in San Diego County.

Meanwhile, clear and quite dry conditions just a short jaunt to
the east over our mountains and deserts, and there`s a distinct
transition in humidity observations from 80-100% under the clouds
to 20-40% in the mountains and deserts. Mid- level easterly winds
around ~850 mb are surfacing over the mountains as winds out of
the east at 10-20 mph, gusts up to 25 mph over the ridges. These
will gradually calm in the afternoon today. Increased mixing at
the surface from these has inhibited overnight cooling, and low
temperatures this morning are noticeably warmer than those of
yesterday in the mountains, especially in San Diego.

High temperatures today will be a few degrees warmer than
yesterday inland from the coast, as has been the trend over the
last couple days. At the larger scale, as low pressure develops
in the Gulf of Alaska and starts to move down the BC coastline,
the smaller low off the central coast will lift north and open
into this larger wave late tonight through Wednesday morning.
Meanwhile, now Hurricane Priscilla will slowly make its way to the
southern tip of Baja CA by Wednesday morning. These will have
little effect on the weather locally until Thursday, and Wednesday
will have similar temperatures today but weaker easterly winds in
the mountains and a stronger onshore push in the afternoon for
some areas (most the lee side of the San Bernardinos into the high
desert).

.LONG TERM (Thursday onwards)...Thursday and Friday, the large
trough in the northeast Pacific will continue to strengthen and
move south. Moisture from Priscilla will filter into south to
southeast CA into AZ as it travels north along the Baja CA
coastline. This will bring the potential for multiple days of
showery precipitation and thunderstorms starting Thursday and
lasting through Friday for most areas, with rain and thunderstorms
possible Saturday as well for the mountains. A few models bring
in the initial wave of showers early Thursday morning, with better
agreement for the late morning into the early evening. This will
also bring the potential for elevated thunderstorms area-wide from
early Thursday afternoon through the evening. National Blend of
Models thunderstorm potential is 15-20% during this period, while
the ECMWF lightning flash density supports the potential for
thunderstorms scattered through the area, including some isolated
flashes along the coast and over the ocean.

More moisture and showers filter in for Friday, though model
solutions of where exactly these move diverge by quite a bit, with
some ensemble members skipping over southwest CA as precipitation
skates south/east of the area. Shower and thunderstorm chances
shift east towards the mountains and deserts over the day Friday
as Priscilla weakens and opens into the large northwest trough.
This continues southeast Saturday, and moisture really starts to
drop off which will limit precipitation chances. There is still
lingering uncertainty with respect to position and amount of
precipitation.

The event precipitation totals from the 25th percentile (75%
chance of receiving at least that much precip) to the 75th
percentile (25% chance of receiving) are quite different. The
25th percentile has dry west of mountains except for a few
hundredths in southern San Diego Co and 0.20-0.40" mostly over
the SD/Riverside mountains into parts of the SD desert. The 75th
percentile by contrast has a much broader swath of 0.10-0.40"
across San Diego County and eastern SBD and Riverside counties,
and 0.50" to just over an inch in the mountains. Chances for an
inch or more in the mountains are 10-20%, highest for more
southern ranges.

There are lingering 15-20% chances for measurable precipitation
over the mountains through Saturday afternoon as the terrain
barrier provides enough lift to help wring out remaining moisture,
along with a smaller chance for more thunderstorms. Temperatures
will start to drop Saturday.

Sunday will almost certainly be dry as dry, stable air settles in
aloft with the trough continuing to move to the east.
Temperatures continue their downward trend for Sunday into early
next week to 5 to locally 10 degrees below daily averages by
Sunday, potentially even 10 to 15 degrees by Tuesday with another
trough dipping south, but confidence in the latter is currently
low.

&&

.AVIATION...
071530Z....Coasts/Valleys...Low clouds with bases 700-1800 feet MSL
and vis reductions of 0-5SM HZ for the inland valleys and hills will
clear inland areas through 17Z. Near the coast clearing expected 17-
20Z, with only partial or intermittent clearing vcnty KSAN and KCRQ.
Low clouds with bases 700-1800 ft MSL and vis restrictions 5 SM or
less expected after 06Z Wed, with a similar inland extent into
portions of the Inland Empire after 10Z Wed. High confidence in base
height/vis reductions and low confidence in timing of cigs.

Mountains/Deserts...Clear with unrestricted vis through
tonight.

&&

.MARINE...
There is a 10-15% chance of thunderstorms Thursday and Friday over
the coastal waters. Occasional northwest wind gusts exceeding 20 kts
are expected Friday afternoon and evening around San Clemente
Island.

&&

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

&&

$$

PUBLIC...CSP
AVIATION/MARINE...CO