Upland, California Weather Forecast Discussion

455
FXUS66 KSGX 232040
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
140 PM PDT Tue Sep 23 2025
.SYNOPSIS...
Warmer today with temperatures reaching the mid nineties in
portions of the inland valleys. Low pressure moving into central
and then southern California will bring cooling for Wednesday
through the end of the week. There could be showers for Friday
and Saturday with the chance for measurable rainfall of 15 to 30
percent. Then dry and gradually warmer into early next week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
This afternoon, the closed upper low is now about 400 miles
southwest of San Diego with decreasing mid and high clouds moving
northwest, and cumulus clouds developing over the mtns. There is
little vertical development of the cumulus clouds due to a stable
environment. A few marine layer low clouds have developed off the
San Diego coast but are not yet moving ashore. Temperatures are
generally higher than at this time yesterday and as much as 16
degrees higher in some inland locations.
From previous discussion...
The closed upper low will move into central California on
Wednesday and into southern California for Thursday night and
Friday. It will bring a cooling trend for Wednesday through Friday
with high temperatures for inland areas 10 to 15 degrees cooler
on Friday than today. Showers/tstms associated with the low will
remain west and north of Orange, San Bernardino, Riverside and San
Diego Counties.
Model solutions remain in good agreement through Sat with respect
to the position and timing of the low to our southwest. As the
low moves southeast across SoCal, it will bring a 20 to 30 percent
chance of showers (mainly in the mountains) for Friday and
Saturday along with a slight chance of thunderstorms. The cooling
trend will continue into Friday with Friday high temperatures as
much as 5 to 10 degrees below average for the mountains and inland
valleys. High temperatures on Friday will range from the lower
70s near the coast to upper 70s to mid 80s for the Inland Empire
with the lower to mid 90s for the lower deserts.
Dry and gradually warmer for Sat into early next week, with
temperatures a few degrees above seasonal averages west of the
mtns on Monday and Tuesday. High temperatures on Monday will
range from the 70s near the coast to around 90 for the Inland
Empire with the mid to upper 90s for the lower deserts.
&&
.AVIATION...
232015Z....Coast...VFR conditions expected along the coast
through 05z when low clouds around 600-1000 feet MSL redevelop and
move inland 5-10 miles. TEMPO groups were added to coastal sites
for possible intermittent cigs around 600 feet MSL and vis 5-6 SM.
More uniform coverage is expected by 12-15z Wednesday, before
clearing by 17-18Z.
Otherwise...VFR conditions continue with SCT clouds 10-15k feet MSL,
and SCT cumulus at 8000 feet MSL over mountains through 01Z. Skies
will be mostly clear after 06z at inland locations with a few clouds
around 25000 feet MSL Wednesday.
&&
.MARINE...
Wednesday and Thursday afternoon/evenings, winds may gust up to
20kts at times near San Clemente Island. Otherwise, no hazardous
marine conditions are expected through Saturday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
PUBLIC...PG
AVIATION/MARINE...Villafane/Zuber

NWS SGX Office Area Forecast Discussion