Fontana, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

960
FXUS66 KSGX 142047
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
147 PM PDT Wed May 14 2025

.SYNOPSIS...
Dry and warm conditions through Thursday. Cooler, cloudier, and
windier with chances of precipitation along and west of the
mountains over the weekend. Warmer conditions with a shallower
marine layer expected next week.
&&

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

Weak troughing will continue over the western United States through
Thursday. Highs Thursday are expected to be 3 to 6 degrees warmer
than today for inland locations. The marine layer is expected to get
a little shallower for Thursday and Friday, but low clouds are still
expected to reach into the western portions of the Inland Empire. On
Friday an impulse will move through the mean flow, deepening the
troughing pattern over Southern California, which will bring a few
degrees of cooling west of the mountains, a deeper marine layer, and
an uptick in westerly winds over the mountains and deserts.

A deeper troughing pattern is expected for the weekend as an upper
low pressure system digs south along the West Coast. There remain
some slight differences in how far south the trough digs but there
is fairly high confidence in cooler weather, increased cloud
coverage, and stronger winds over the mountains and deserts. NBM
chances for wind gusts reaching or exceeding 50 mph are 40 to 60
percent for the desert mountain slopes and into the deserts, with
chances closer to 95 percent in wind prone locations in those
geographic areas. A ridge of high pressure will set up over the
Eastern Pacific for the weekend. Model guidance is suggesting
subtropical moisture will be pulled over the ridge and into Southern
California as the aforementioned trough digs south. The increased
moisture will bring chances of precipitation to the area. Due to the
predominately northwesterly flow, highest chances of precipitation
are along and west of the mountains for San Diego county, with
second highest chances for precipitation on the coastal slopes of
the San Bernardino and Riverside county mountains. NBM chances of
rainfall totals exceeding 0.10" Saturday night through Sunday for
San Diego county coast, valley, and mountains and Riverside/San
Bernardino mountains are 20 to 40 percent, with the highest chances
on the coastal mountain slopes. Elsewhere chances are 10 percent or
less. For total rainfall accumulations between Saturday evening and
Sunday it looks unlikely more than 0.25" will accumulate for San
Diego coast/valleys. For the coastal mountain slopes, it is unlikely
total rainfall will exceed 0.50".

Dry conditions are expected to return to the area by Monday, as the
trough moves east and upper level ridge inches closer to the West
Coast. By Tuesday, the majority of ensemble clusters show ridging
over the West Coast. Current forecast follows the NBM with warming
temperatures for Monday through Wednesday. By Tuesday and Wednesday,
high temperatures will be around average for the mountains and
around 4 to 8, locally up to 10 degrees above average for the coast,
valleys, and deserts.

&&

.AVIATION...
142030Z...Coast/Valleys...Low clouds redevelop from south to north
after 06z Thursday with bases 1500-2000 ft MSL. Clouds should remain
over the coasts and western valleys, likely not reaching KONT, and
scattering to the coastline around 16-18z. Otherwise, typical flow
pattern with light seabreeze winds each afternoon.

.Mountains/Deserts...SKC today and tonight. Typical flow
pattern through Thursday with westerly winds gusting 25-35 kts
through mountain passes each evening.

&&

.MARINE...
No hazardous marine conditions are expected today through Saturday.
Stronger winds and higher seas are expected late Saturday into
Sunday. Winds 15 to 25 kts expected in the outer coastal waters with
steep, wind-driven waves 7 to 10 feet for outer coastal waters and 5
to 8 feet for inner coastal waters. Winds and waves slowly
begin to subside late Sunday into Monday.

&&

.BEACHES...
Elevated to potentially high surf will impact beaches Sunday into
Monday. Surf height 4-7 feet expected with sets to 8 feet along west-
facing beaches.

&&

.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...CO
AVIATION/MARINE/BEACHES...KW