854
FXUS66 KSGX 091207
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
507 AM PDT Fri Oct 9 2026

.SYNOPSIS...
Cooling will spread inland into the weekend with high temperatures
lowering to around average on Saturday. High temperatures for the
coast and valleys will be mostly in the 70s for Sunday through
Tuesday. One low pressure system from the southwest on Sunday and
a second from the north on Monday and Tuesday combined with
tropical moisture will bring showers for late Saturday night
through Sunday night with continuing chances for showers through
Tuesday night. There will also be stronger southwest to west winds
on Sunday.

&&

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


...UPDATED AVIATION DISCUSSION FOR 12Z TAF ISSUANCE...

As of 12:30 AM local time, a few low clouds were covering parts of
coastal San Diego County. Perhaps some very localized fog exists
where clouds and terrain are intersecting, reducing visibility`s
below 1 mile. Nearly 800 nautical miles to the southwest,
Tropical Storm Rachel has begun its turn northeastward moving at
less than 10 miles per hour. Its path will have a significant
influence on the upcoming weather as its remnants and surface low
pressure approach the west coast of North America.

Temperatures...Today marks the last day of significant heat
(especially in the low deserts) before a significant pattern change
to the region, regardless of the tropical activity. What is most
certain in this forecast is that temperatures are bound to cool off
significantly into early next week. Highs today fall a few degrees
from yesterday - 80s coastal / mid-90s inland / 100s low desert - as
a closed upper low and broad west coast trough dip into California.
Broad cloud coverage from Rachel`s remnants during the day Saturday
drop highs around 10 degrees from Friday. The trough continues to
deepen Sunday, dropping highs another 5-10 degrees and then finally
the trough axis moves over SoCal on Monday, bringing the coolest
temperatures some areas have seen since last April. The current
forecast has high temperatures Monday in the mid/upper 60s across
the coastal basin and high deserts with highs in the 40s in the
mountains and 70s in the low deserts. If the closed low positions
itself over Socal instead of the Great Basin as the GFS is showing,
we could see 700mb temperatures around -5 C and highs could be even
a few degrees cooler than forecast. Minimum temperatures are also
expected to drop a few degrees each night inland, from around 70
this morning to around 50 for early Tuesday (and to the upper 50s
at the coast).

Rainfall...Tropical Storm Rachel approaches the coast this weekend,
bringing a chance for an initial soaking rain Sunday. The broader
trough very slowly moves through Monday with its own moisture and
mid-level vorticity from the trough axis could bring another round
of showers Monday into Tuesday. The first wave comes from TS
Rachel, which is timing periodic rainfall between 1 AM-5 PM
Sunday. While there isn`t much background instability (almost no
CAPE), PWAT`s will generally range from 1.3-1.8 inches (>2 inches
for high end scenario) and the surface low could generate periods
of persistent moderate rainfall with rain rates over 0.5 in/hr in
the mountains. Rainfall amounts from TS Rachel will largely depend
on its track, especially for some of the mountain areas. If the
surface low from TS Rachel landfalls farther south (>100 miles
south of SD) and it continues to track east, the amount of
rainfall especially in the coastal basin and desert slopes would
be very limited as there is initially not much instability to
generate rain. Based on NBM probabilities, this scenario
represents around 25% of solutions, yielding to rainfall less than
0.25" for the entire coastal basin and less than 0.10" for areas
farther west like Orange County. The most likely scenario,
accounting for around 50% of solutions, brings the coastal
basin/deserts a soaking rain between 0.25-1" during this first
wave with 1-2 inches in the mountains. Assuming the low tracks
close enough to the mountains, easterly flow over the desert
slopes could yield surprisingly high rates (>0.5/hr) and totals
(1-2 inches). The higher end case (~25% chance) brings 1- 2" over
the coastal basin/deserts and 2-4" over the mountains, which could
result in more numerous impacts across the region. The remnants
of TS Rachel should move out of the region quickly Sunday evening,
yielding breaks in rainfall. The following waves of showers
Monday and Tuesday will be driven by the upper level dynamics of
the trough and will feature a much drier airmass. Totals
Monday/Tuesday should look more similar to a light wet season
system: 0.10-0.25" for the coastal basin, higher amounts in the
mountains and less than 0.10" for desert communities. Since the
trough will drive in much colder air, light snow accumulations are
possible with this second round above 8,000 feet.

Winds...There is similar uncertainty with the winds. A track farther
southeast would yield to much lighter winds gusting below 20 mph
through the coastal basin while the most likely scenario (~50%
chance) that the surface low makes a close approach yielding to wind
gusts 20-40 mph through the coastal basin, with gusts 50-70 mph in
the mountains and passes during the day Sunday. Winds remain onshore
Monday but much less strong than Sunday.

Once the trough passes through the region, temperatures rebound
through the end of next week as the active weather clears.

&&

.AVIATION...
091200Z...Coast...Patchy low clouds with bases 500-900 ft MSL are
increasing in coverage at this hour and will spread up to 10 miles
inland by 15Z. Areas of vis 1-5 SM on the coastal mesas and far
western valleys. Clouds clearing to the coast with vis becoming
unrestricted 15-17Z. Patchy low clouds returning to the coast after
03Z Saturday with bases closer to 1000-1500 ft MSL.

Otherwise...Mostly clear with unrestricted vis through Friday
evening.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday. Gusty
northwest to west winds developing Sunday then weakening on Monday.
Wind gusts 20-30 kt and choppy seas will produce conditions
hazardous to small craft on Sunday.

&&

.BEACHES...
Surf of 3-5 feet with sets to 6 feet will continue on south and
southwest facing beaches through Friday. Elevated surf and strong
rip and longshore currents will create hazardous swimming
conditions. This elevated surf will combine with high tides during
the mornings and evenings to produce local coastal flooding and
beach erosion.

Another south swell arriving Sunday along with wind waves and
continued morning high tides near 7 feet will maintain a threat of
coastal flooding and beach erosion into Tuesday. Surf on Sunday is
currently expected to be 5 to 7 feet with local sets to 9 feet,
decreasing to 3-6 feet for Monday and Tuesday. There is still a lot
of uncertainty in exact surf heights. The Beach Hazards Statement
and Coastal Flood Advisory contain more details.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through this evening for Orange County
     Coastal Areas-San Diego County Coastal Areas.

     Coastal Flood Advisory until 2 PM PDT Tuesday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

     Extreme Heat Warning until 8 PM PDT this evening for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass near
     Banning.

PZ...None.

&&

$$

PUBLIC...Westerink
AVIATION/MARINE/BEACHES...PG

NWS San Diego (SGX) Office