854
FXUS66 KSGX 091001
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
301 AM PDT Fri May 9 2025

.SYNOPSIS...
Dry weather with significant warming will continue through
Saturday with Saturday high temperatures as much as 20 to 25
degrees above average for the Inland Empire. A large low pressure
system moving to near the West Coast will begin spreading cooling
inland on Sunday. Greater cooling is expected for Monday and
Tuesday with Tuesday high temperatures as much as 15 to 20 degrees
below average for the mountains. The marine layer will decrease in
depth to around 1000 feet for Saturday, then rapidly deepen to
5000 to 6000 feet for early next week with coastal low clouds
spreading onto the coastal slopes of the mountains by Tuesday.
There will be stronger and gusts southwest to west winds for the
mountains and deserts for Monday and Tuesday. High temperatures
will warm 5 to 10 degrees for Wednesday and Thursday, but remain
several degrees below average.

&&

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

.SHORT TERM (Friday through Sunday)...
High pressure aloft will bring significant warming today with
Saturday high temperatures another few to around 5 degrees warmer
than today. Saturday is expected to be the warmest day. With the
warming, high temperatures on Saturday will range from the mid to
upper 70s near the coast to 100 to 106 for the Inland Empire with
104 to 108 for the lower deserts. Cooling will begin to spread
inland on Sunday with Sunday high temperatures 5 to 10 degrees
cooler than Saturday for the coast and valleys.

The marine layer will continue to slowly decrease in depth into
Saturday. For land areas, the greatest coverage of low clouds for
for this morning is expected for San Diego County from the coast
inland to around the mesas with the fog locally dense near the
mesas and other higher coastal terrain. Similar areas are expected
to have low clouds and fog for late tonight into Saturday
morning, but with patchier coverage. Less certain is how much
deepening and inland spread of the coastal low clouds will occur
for Saturday night into Sunday morning. The most likely scenario
is for the low clouds to return into portions of the western
valleys for Sunday morning.

&&

.LONG TERM (Monday through Thursday)...
A large low pressure system moving inland along the West Coast
will be centered near the West Coast on Sunday night and Monday.
This system will continue to move slowly inland and amplify into
southern California on Tuesday. This will be followed by a
gradual weakening of the low pressure system for Wednesday and
Thursday.

Cooling will continue to spread inland on Monday with additional
cooling for Tuesday. With the cooling, high temperatures on
Tuesday will be as much as 15 to 20 degrees below average for the
mountains. High temperatures on Tuesday will range from the lower
to mid 60s near the coast to the 60s for the valleys with the
lower deserts in the mid 70s to lower 80s.

Warming is expected for Wednesday and Thursday. Thursday high
temperatures will still be several degrees below average with high
temperatures ranging from the mid 60s near the coast to the lower
to mid 70s for the Inland Empire with the lower deserts in the mid
80s to lower 90s.

Night and morning coastal low clouds are expected to return to
portions of the inland valleys by Monday morning, then onto the
coastal slopes of the mountains for Monday night and Tuesday. For
Wednesday and Thursday, the marine layer won`t be quite as deep,
but coastal low clouds will spread into portions of the inland
valleys for Wednesday night into Thursday morning.

There will be stronger onshore flow for Monday and Tuesday with
stronger and gusty southwest to west winds for the mountains and
deserts. The stronger gusts, to 45 to 55 mph, are expected in the
northern Coachella Valley below the San Gorgonio Pass with
isolated gusts to 60 to 70 mph.

&&

.AVIATION...
090900..Coasts/Valleys...Low clouds based at 400-600 ft MSL have
moved into San Diego County coastal areas, and will spread into
parts of the Orange County coast with a 60% chance for impacts at
KSNA by 12Z this morning. Vis reductions to 3-6 SM are likely along
most of the coast, with local reductions to 1/2-2 SM over the
coastal highlands, especially 11-14Z this morning. Clouds clear to
the beaches 15-17Z. Patchy low clouds redevelop along parts of the
coast after 06Z Sat, but confidence in clouds making it into any of
the coastal sites is low, with a 10-30% chance for impacts at any
one site. Bases of clouds that do develop will be lower than this
morning, 200-500 ft MSL with greater vis reductions.

Mountains/Deserts...Mostly clear with VFR conditions today and
tonight.

&&

.MARINE...
Low clouds and patchy fog may bring visibilities to 1-3SM over the
waters tonight into Saturday morning. Otherwise, no hazardous marine
conditions are expected through Tuesday.

&&

.CLIMATE...
High temperatures today will be around 20 degrees above average
for the Inland Empire and as much as 20 to 25 degrees above
average on Saturday for the Inland Empire. Several high
temperature records could be tied or broken on Saturday with the
most likely locations to set new records for the date being Ramona
and Palomar Mountain.

There could be also several record warm minimum temperature records
for Saturday tied or broken as well with the most likely locations
to set new records for the date being Riverside, Alpine,
Idyllwild, and Lake Cuyamaca. Several degrees of cooling will
begin to spread inland on Sunday with much cooler conditions for
Monday and Tuesday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 10 AM this morning to 9 PM PDT Saturday for
     San Bernardino and Riverside County Valleys-The Inland
     Empire.

PZ...None.

&&

$$

PUBLIC/CLIMATE...17
AVIATION/MARINE...CSP