South Fontana, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

688
FXUS66 KSGX 040514
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
914 PM PST Tue Dec 3 2024

.SYNOPSIS...
Cooler Wednesday as an upper level low moves over. Low clouds are
expected to reach into portions of the valleys tonight into
Wednesday morning. The marine layer will become shallower for
Thursday and Friday. Warmer and drier conditions with weak to
locally moderate northeasterly winds Friday and Saturday. Dry
conditions will continue into early next week, with the potential
for additional rounds of Santa Ana winds.

&&

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

Evening update...
Low clouds have returned to the coastal areas this evening and
have already begun to spread into portions of the western valleys
in San Diego County. The 00Z KNKX sounding shows the base of the
marine inversion has risen to around 1900 ft MSL, deep enough that
any fog will be very localized tonight. Otherwise mostly clear
skies and light winds overnight.

Previous discussion...
The marine layer will start to become shallower Wednesday
night into Thursday with the return of weak offshore flow, keeping
areas of low clouds and fog mostly confined to coastal areas. Areas
of low clouds are expected again Thursday into very early Friday
before breezy northeast winds develop.

Highs on Wednesday are expected to be a few degrees cooler than
today. Even with the slight cooling, temperatures away from the
coast will remain above average. Warming is expected for Thursday
through Saturday.

High pressure will build aloft just off the US West Coast for Friday
and Saturday with an area of low pressure aloft over Arizona and
northern Mexico. Weak to locally moderate northeast winds are
expected, along with warm and dry conditions. High temperatures
Friday and Saturday will be 7 to 15 degrees above average. Peak wind
gusts will likely be 35 to 45 mph on the coastal slopes of the
mountains, mountain foothills, and locally into the eastern valleys.

Early next week, an area of low pressure will dig south into
northern United States, with a ridge of high pressure near the US
West Coast. There is still a lot of uncertainty on where the low
will end up. For Monday, about 50 percent of solutions have the low
digging into the Great Basin, with 50 percent showing the low`s
position further east and digging into the Upper Midwest. The
uncertainty continues for Tuesday, with about 55 percent of ensemble
solutions showing the low digging into the Four Corners region with
the other 45 percent showing the low further east over the Midwest.
The ultimate placement of this low will determine how strong any
Santa Ana winds that develop would be. The overall pattern will also
have an impact on temperatures for early next week. If the ridge
axis is centered more over the US West Coast, the forecast will
trend warmer with cooler solutions more likely if the low digs south
into the Great Basin/Four Corners and the ridge axis stays just
offshore. Current forecast follows the NBM for early next week. Dry
conditions look likely to prevail into early next week.

&&

.AVIATION...
040415Z....Coasts/Valleys...Satellite shows low clouds and fog
building along the coast which will push up to 15 miles inland
overnight. Bases generally around 800-1200ft MSL with some slight
lowering at times between 10z-15z. VIS may fall to 4-6SM along the
coast, locally lower at times, with VIS down to 0-3SM for western
valley areas and coastal terrain. Clearing/lifting should begin
around 18z-19z Wednesday, although low stratus will linger along the
beaches beyond this period. Low clouds build inland again Wednesday
night, continuing into Thursday morning.

Mountains/Deserts...FEW-SCT high clouds at or above 15,000 feet MSL
through tonight, clearing by Wednesday morning. Otherwise, mostly
clear skies and VFR conditions prevail through Wednesday afternoon.

&&

.MARINE...
No hazardous marine weather conditions are expected through
Sunday.

&&

.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...SS/CO
AVIATION/MARINE...Zuber