813
FXUS66 KSGX 070531
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
931 PM PST Tue Jan 6 2026
.SYNOPSIS...
Periods of isolated light to locally moderate rain showers will
continue into Wednesday, most likely across San Diego county. Gusty
west to northwest winds are expected for Wednesday evening into
Thursday, strongest for the desert mountain slopes into the deserts.
Santa Ana winds will quickly develop Thursday afternoon/evening and
strengthen Friday through the weekend. Warm days west of the
mountains can be expected Friday into early next week with cold
nights in the deserts and any wind sheltered locations in the
valleys and mountains.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Update: Latest radar imagery has just a few light showers moving
over some of the inland areas of San Diego County. Most of the
shower activity is remaining well offshore as the U/L low
continues to propagate further south. There are some showers
beginning to appear and move in from the south towards San
Clemente Island. As the night progresses and the low begins to
move eastward, these showers will likely begin to transition
eastward as well and eventually over most areas of San Diego
County. The latest model guidance has been trending dryer,
especially the HRRR, although this model has done an inadequate
job verifying initially. The WRF has kept most of the shower
development confined to the San Diego County mountains in the
morning, and then transitioning to more onshore shower activity by
later in the afternoon. Rainfall rates with the more moderate to
heavier side may have rates up to 0.25-0.35 at the most, while
other rates will generally remain much lower, so not expecting
significant rainfall amounts unless a shower (or possibly a
thunderstorm) remains nearly stationary. Expect lesser amounts for
most of San Diego County to likely be no more than 0.1-0.2 inches
of rainfall through tomorrow evening, and then amounts will taper
to even lesser amounts going into Orange and Riverside counties,
an likely remaining mostly dry for San Bernardino County.
The rest of the forecast appears to be on track with the "inside
slider" trough passing by on Thursday enhancing the onshore flow and
creating rather strong and gusty winds which may reach High Wind
criteria for some of the higher elevations and where stronger winds
are more prevalent due to gap flow. This will transition to offshore
winds going into the weekend and the warming and drying trend looks
to continue going into the mid part of next week.
Previous discussion submitted at 141 PM:
Widespread mid to high cloud coverage is expected into Wednesday as
a closed upper level low continues to move south today, before
moving east into northern Baja tonight. The highest chances of
precipitation this evening into Wednesday are across San Diego
County, including the San Diego County desert. Any rainfall tonight
into Wednesday should be light to locally moderate, with peak
rainfall rates 0.10-0.35" per hour. Rates at the higher end of the
that range are most likely to occur in San Diego county. Rainfall
totals from tonight through Wednesday afternoon will range from 0.05-
0.35", with totals on the higher end of that range expected in far
southern San Diego County. Snow will fall above 7,000 feet in the
mountains, with very little if any sticking in the Riverside County
mountains. Showers should become more localized to the mountain
slopes of the Riverside and San Diego mountains by Wednesday
afternoon with dry conditions expected to return by Wednesday night.
A fast-moving inside slider will move through the interior West
Wednesday night into Thursday. Latest guidance has the track of this
inside slider further south and west which has resulted in a
significant increase in our wind forecast for Wednesday night into
Thursday. Gusty westerly winds are expected for the mountains and
deserts. Wind gusts for the desert mountain slopes will peak at
around 50-70 mph (potentially locally higher in west wind favored
locations) with gusts in the deserts peaking at 40-55 mph. As the
upper level low settles over the Four Corners region Thursday
afternoon/evening northerly offshore flow will quickly develop as
high pressure aloft rapidly amplifies along the West Coast and cold
air produces strong surface high pressure over the Great Basin. This
initiates what looks like a prolonged period of offshore flow that
will continue into next week at least.
Winds will become more northeasterly Friday through the weekend as
the main driver of the Santa Anas becomes the pressure gradient
between Southern California and the Intermountain West. Latest
ensemble guidance has trended slightly stronger with Friday`s winds
but winds continue to look strongest and most widespread over the
weekend when the surface high peaks in strength. Moderate to locally
strong northeast winds look possible Friday through Sunday. There is
some potential for moderate strength Santa Ana winds to continue
into Monday, but chances decrease from 40-60% over the weekend to
around 20-30% on Monday. Thankfully, due to all the rain we`ve
received in December, fire weather conditions will likely only
remain elevated due to gusty winds and minimum relative humidity
falling to the teens. Fuel moisture will be above critical levels.
In addition to the gusty Santa Ana winds, high temperatures for the
coast and valleys will reach the 70s to locally low 80s by early
next week. Low temperatures in the deserts and wind sheltered
locations in the valleys and mountains are expected to fall to the
30s and low 40s, even as low as the upper 20s in the High Desert.
Based on the current forecast, the coldest mornings are looking to
be Friday through Sunday. Overnight lows should increase slightly
for early next week as the surface high weakens, resulting in less
cold air advecting into our local deserts. From Friday onward,
marine layer low clouds and fog are expected to be absent from
coastal areas due to the dominate offshore flow. &&
.AVIATION...
070520Z...VFR conditions and FEW-SCT clouds near 5000-1000 MSL for
much of the area. Additional round of SHRA expected over southern
and central parts of the forecast area, including VCTY KPSP/KTRM,
through Wednesday afternoon , spreading from south to north.
Greatest SHRA activity in SD County after 13Z Wed; heaviest SHRA
will linger off the coast. Accompanying this precipitation is likely
brief CIGs near 1500ft MSL and VIS reductions to 2-5SM in areas of -
RA/RA. -SHRA departing the area after 03Z Thursday.
West winds increasing across the mountains and deserts after 00Z
Thursday. Wind gusts across the deserts 25-40 kts and 40-55 kts
across the desert slopes and passes will create MOD/STG UDDFS
through much of Thursday.
&&
.MARINE...
Breezy northwest winds gusting to 30 knots in the outer waters
expected Wednesday night into Thursday afternoon near San Clemente
Island. Steep 8 to 11 feet seas with an 8-9 second period will occur
in the outer waters from Wednesday night through Thursday night.
Otherwise, no hazardous marine conditions forecasted through this
weekend.
&&
.BEACHES...
Surf 4-6 feet with sets to 8 feet expected Thursday afternoon and
Thursday night for west facing beaches in San Diego county. Surf
diminishes Friday morning.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch from Wednesday evening through Thursday evening
for San Bernardino County Mountains.
High Wind Watch from Wednesday evening through Thursday
afternoon for Riverside County Mountains-San Diego County
Mountains-San Gorgonio Pass near Banning.
Wind Advisory from 8 PM Wednesday to 1 PM PST Thursday for Apple
and Lucerne Valleys-Coachella Valley-San Diego County
Deserts.
PZ...Small Craft Advisory from 4 PM Wednesday to 10 PM PST Thursday
for Waters from San Mateo Point to the Mexican Border
Extending 10 to 60 nm out including San Clemente Island.
&&
$$
PUBLIC...CO
AVIATION/MARINE/BEACHES...APR
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