777
FXUS66 KSGX 110339
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
839 PM PDT Thu Jul 10 2025

.SYNOPSIS...
Hot inland and cool at the coast for the rest of today. Friday
will cool a little, with minor day to day changes through the
middle of next week. A deepening marine layer will bring more
coastal clouds extending farther inland during the nights and
mornings.

&&

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

Update: The forecast looks to remain on track with the ridge
breaking down slightly as a trough deepens from the north with a
gradual cooldown beginning tomorrow and going into the weekend. This
will help to cool down temperatures and also help to lift and
thicken the marine layer a bit, especially by early next week, with
only a slight uptick in temperatures on Sunday as the high pressure
center becomes situated over the SOCAL bight. 500 mb heights are not
going to deviate too much early next week, so high temperatures
should remain nearly constant from Monday through Thursday of next
week. There is some indication that monsoonal moisture could make
its way over the region on Thursday of next week as mid-level
flow becomes more southeasterly and provides a very slight chance
of thunderstorms developing over the mountains during the
afternoon hours. Other than that, conditions will remain dry
elsewhere throughout the next week.

(Previous discussion submitted at 144 PM):

Temperatures were running very similar to those yesterday as of
midday, some a little higher and others a little lower. Deserts
are a little cooler, while many inland valleys are a little
warmer. Areas of low clouds are sticking to the beaches in San
Diego County. Temperatures today show a great contrast from the
temperate coast to the scorching desert. The midday temp was 67 at
Oceanside Harbor and 114 in Ocotillo Wells. While it doesn`t
appear desert temps will reach those record levels of yesterday,
extreme heat warnings are warranted and still in place for the
lower deserts through sunset. In the valleys, highs will be in the
90s to about 106 and a heat advisory is out today, particularly
for the more inland valleys where a few temps in spots already
exceed 100. These inland highs represent 6 to 12 degrees above
normal today. A Heat Advisory remains in effect through sunset. A
temporary but strong ridge overhead has brought our region the
kind of subsidence and compressional heating needed for this heat
episode. This should be the final day of extreme heat. This high
will weaken slightly Friday, and some additional gulf moisture
creeps into the lower deserts, allowing for a drop of several
degrees, but still up to 8 degrees above normal in the low desert
for mid July. Valleys will trend close to normal for the weekend.
The marine layer will get a boost by a coastal eddy tonight and
Friday to rebuild and extend low clouds and fog into western
valleys and for a longer time each night and morning. For next
week, minor variations in the upper high will maintain this rather
seasonal weather, except slightly hotter than average in the
deserts. There are hints of monsoon moisture increasing next
Wednesday through Friday for an extremely slight (but nonzero)
chance of showers and thunderstorms across the southern interior.
We`ll need more consistency and consensus in ensemble solutions
that far out to add precip to the forecast.

&&

.AVIATION...
110330Z....Coast/Valleys...Low clouds fill back in and push ashore
tonight after 04Z, based 1100-1500 ft MSL, moving inland to about 15
miles inland. 55% chance for cigs at KSNA by 10Z tonight. Scattering
back to the beaches by 16-18Z, but patchy clouds will linger along
the beaches through the afternoon. Clouds with similar bases move
inland again after 02Z Sat.

Mountains/Deserts...VFR conditions and unrestricted VIS through
Friday.

&&

.MARINE...
No hazardous marine conditions expected through Monday.

&&

.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...MM
AVIATION/MARINE...CSP