Bostonia, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

917
FXUS66 KSGX 180458
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
858 PM PST Wed Dec 17 2025

.SYNOPSIS...
Warm weather will continue across the region with patchy fog
closer to the coast through Friday with gusty winds across the
high desert today. A subtle cooling trend will occur over the
weekend as high pressure weakens over the area, though
temperatures will remain above normal. A low pressure system will
bring increasing chances for rain by Tuesday, with heavier rain
possible around the Christmas holiday.

&&

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

Update: At this time, low clouds and fog have continued to struggle
to reform and fill back in along the coastal areas this evening,
with the only significant banding of clouds being located right
along the stretch of beach from Camp Pendleton down to Cardiff by
the Sea. This is partially due to weak offshore winds, which will
continue to inhibit some of these low clouds and fog from forming
throughout the night. There will be some patchy areas of dense
fog likely forming along the immediate coastline going into the
early morning hours, especially for San Diego County. The marine
layer should continue to fill in northward and stretching about 5
to 10 miles inland, and depending on how (and where) this ends up
developing will also determine how quickly it scatters out. A
consensus of the high res models has everything clearing out by
around 10 AM tomorrow. The forecast still remains on track with
cooling through the weekend and into early next week, along with
some possible drizzle for the coastal and inland areas by Monday,
and then a large area of low pressure will slowly advance towards
the region, with the possibility of some showers associated with
this system to begin as early as Tuesday morning of next week, and
then chances of precipitation increasing thereafter going into
the latter half of next week as temperatures also continue on a
cooling trend through then.

Previous discussion submitted at 114 PM:

Low clouds and fog continue to be intermittent near the coastline,
with a slow clearing trend observed on satellite this afternoon.
The flattening of the ridge aloft will create a slightly stronger
pressure gradient, where winds will be gusty near 30-40 MPH across
the high desert through this afternoon. The hazy and foggy trend
will continue through the afternoon before clouds begin to build
back into the these areas early this evening, highest chance of
fog again across coastal San Diego County. Models suggest clouds
may dissipate before sunrise as weak offshore flow occurs over the
region as well. This is all due to high pressure over the area
increasing in strength. This will also bring greater warming
across the region by Thursday, which will be the last very warm
day for awhile. High temperatures will be close to 20 degrees
above average by Thursday, where places like Borrego Springs, Big
Bear, Alpine and Idyllwild may see record high temperatures for
the day.

The high will weaken by Friday, with winds turning back onshore.
This will bring a few degrees of cooling for areas west of the
mountains with most of the mountain and desert areas remaining
unchanged, where highs remaining 15 to 20 degrees above normal.
The high will continue to push southward as a weak atmospheric
river and trough to the north begin to move across Northern
California and the Pacific Northwest. The high will continue to
dominate our weather pattern through next Monday with night and
morning low clouds near the coast and high temperatures well above
normal. The lower deserts will still see highs in the lower 80s
on Monday with plentiful 70s across the valleys and high desert.

The moisture plume and trough of low pressure to the north will
move southward by the middle of the week, combining into a
stronger and deeper area of low pressure. NBM brings in chances
for precipitation starting Tuesday into Tuesday night across the
region, with more widespread precipitation expected by Wednesday
and Christmas Day. The timing of this system still remains highly
uncertain based on the nature of the ridge the departing ridge to
the south and where exactly the area of low pressure sets up. It
is definitely plausible that the low deepens enough to stay off to
the west and north through Tuesday, which wouldn`t bring any rain
to the area until Wednesday. Though confidence in rain totals is
low, there has been an upward trend in rainfall over the past
couple of days. Heaviest rainfall is expected to be over the
coastal basin. Chances for total rainfall over 2 inches ranges
from 35-55% in Orange County and the Inland Empire, closer to
20-40% across San Diego County. As of now, model guidance points
to later on Christmas Eve into Christmas Day seeing the heaviest
precipitation. But if the system stalls at all or remains further
off the coast, the heaviest rainfall may be pushed back in time
where precip may continue into next Friday or beyond. Confidence
continues to increase that bouts of heavy rainfall will lead to an
increased flood and debris flow risk, as well as holiday travel
disruptions for the entire region.

&&

.AVIATION...
180430Z...Coast/Western Valleys...Low clouds based 500-900 ft MSL
along the immediate coast will continue to reform and push into
coastal San Diego County, and eventually northward into Orange
County. Minor vis restrictions initially (2-5SM) will slowly worsen
again as bases lower after 06Z with areas of dense FG becoming
likely, especially along the immediate coastline. FG may expand to
include Orange County after 06Z (40%) but coverage will become
patchier with FG likely retreating from most land areas 12-15Z.
Patchy FG through 18Z over coastal waters.

Otherwise...VFR conditions today and tonight. Elevated winds in the
High Desert gusting 25-35 kts through 06Z Thu. These winds will
increase again tomorrow, with similar

&&

.MARINE...
Areas of fog and low visibility (less than 1SM) returning late this
evening and overnight as clouds lower again. Fog will likely become
more patchy overnight and scatter out by mid morning Thursday.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

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

&&

$$

UPDATE...Stewey
PUBLIC...APR
AVIATION/MARINE...Stewey