Ontario, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

628
FXUS66 KSGX 182034
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
134 PM PDT Fri Apr 18 2025

.SYNOPSIS...
Hit-and-miss showers continue through this evening, most likely
over the mountains, parts of the high desert, and southern San
Diego County. After a cloudy, cool, and breezy day today, dry and
warmer conditions are on tap for the weekend into early next
week, with high temperatures near to around 5 degrees above
average by Monday. Gradual cooling follows Tuesday through Friday.

&&

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

.SHORT TERM...Today (Fri 18) through Sun 20...

A large scale upper level low is over the western U.S. today,
bringing cloudy, cool, and breezy weather. Radar this afternoon
shows a few small showers moving eastwards across southern San
Diego from the coast to the mountains. Mostly cloudy skies
through most of the region mountains westwards will continue
through late this evening, with only partial, intermittent
clearing this afternoon, mostly for northern coastal areas.

As the upper low pressure continues to move into the desert
southwest late this afternoon and evening, isolated showers will
develop over the mountains and northeast high desert, with slight
chances for eastern inland valleys and western foothills as well,
while showers along the coast taper off. Additional rainfall
totals for the rest of today will be on the lighter side, 0.05"
to locally 0.25", and snow from a trace up to half an inch will
be limited to mountains above 7000 to 7500 feet. The low will also
keep west to southwest winds on the gusty side over the mountains
and deserts today, and maximum wind gusts will peak at 30 to 45
mph late this afternoon through the mountain passes. Winds weaken
late this evening.

Showers, where present, end late tonight, and skies will mostly
clear overnight as a weak ridge starts to build in. Mostly clear
skies with warmer high temperatures near normal for the coastal
areas and up to 5 degrees below for inland areas follow Saturday.
Seasonally average afternoon breezes are expected, with a
stronger sea breeze than previous days. Some patchy low clouds
will develop near the coast overnight Saturday into Sunday, but
mostly clear skies will predominate for most areas.

&&

.LONG TERM...
Temperatures will continue to increase Sunday and Monday, and high
temperatures will be near normal for coastal regions and about 5
degrees above average for inland areas by Monday. Coastal areas
cool off slightly Tuesday, and the cooling trend spreads inland
Wednesday through Friday, with overnight and morning low clouds
and patchy fog that will gradually get slightly deeper and further
inland towards mid-week. Afternoon high temperatures will be back
to 5-10 degrees below average for this time of year by the late
week.

Ensemble weather models are in good agreement through late Saturday,
with differences in the placement of an upper low pressure after
that. A minority of model outputs indicate precipitation around
Sunday-Monday, while the majority keep us dry if cooler than
average.

&&

.AVIATION...
182000Z....Coasts/Valleys/Foothills...Multiple cloud layers with SCT
to locally BKN clouds 1500-3000 feet MSL, and a BKN-OVC cloud layer
at 5000-8000 ft MSL. ISO -SHRA possible through 22Z for the valleys
and 00Z Sat for the mountain foothills. Higher terrain will be
obscured in FG up to 8000 feet. Partial scatter out likely for the
coast and valleys through the afternoon, with a gradual clearing
overnight into Saturday.

Higher Mountains/Deserts...Areas of high clouds across the High
Desert through 00Z, with clear skies elsewhere. Westerly winds with
gusts 25-35 kt, locally up to 45 kt through and below passes will
continue through 00Z Sat. Strong up/downdrafts and isolated LLWS in
lee of mountains such as vcnty KPSP.

&&

.MARINE...
No hazardous marine conditions are expected through Tuesday.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...CSP
AVIATION/MARINE...CO