Etiwanda, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

299
FXUS66 KSGX 131140
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
440 AM PDT Sun Sep 13 2026

.SYNOPSIS...
A cooling and drying trend will occur across the region into the
weekend and early next week. This will be accompanied by a building
marine layer with clouds returning closer to the coastal areas each
night and morning. An area of high pressure may strengthen by the
end of next week, nudging temperatures back above average.

&&

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


...UPDATED AVIATION DISCUSSION...

The 00z San Diego sounding shows a well mixed marine layer in the
lowest 2,000 feet of the atmosphere with a strong inversion above
it. Nighttime satellite imagery also shows this as tonight`s
clouds are filled in over a very broad extent, from over the
coastal waters up to 20 miles inland throughout SD County and
Orange County. Clouds are likely to eventually reach into the
Inland Empire in the early morning hours. Communities like
Riverside, Ontario and possibly San Bernardino will wake up to a
low stratus deck overhead. Nighttime temperatures are generally
running 2-7 degrees cooler than yesterday at this time, with
morning lows expected to reach below 70 degrees across the coastal
basin for the first time in over a week.

Today`s temperatures will be similar to yesterday`s (maybe a degree
or two cooler inland) : upper 70s near the beaches, 80s in coastal
areas, low 90s inland, mid-to-upper 90s in the IE and high desert
and 100s in the lower deserts.

The trough over the PacNW which is bringing cooler weather to SoCal
looks to move through fairly slowly, maintaining its influence
through Monday. While the main trough elongates over Canada and
moves eastward, the GFS and ECMWF show another lobe of cool mid-
level air dropping down straight south out of British Columbia and
ejecting out of the main jet stream. This lobe looks likely to
become a closed upper low over NorCal and Oregon Wednesday and
Thursday, which would keep temperatures close to average despite
the ridge over the southeastern US intensifying and expanding
westward.

WPC 500mb height clusters indicate high confidence that this
ridge will eventually build Friday and Saturday, increasing temps
around 5-15 degrees above average into next weekend.

Throughout the forecast period, winds remain likely onshore with a
coastal eddy spinning through Wednesday and typical late afternoon
south and west winds over desert slopes.

&&

.AVIATION...
131130Z...Coasts/Valleys...Low clouds based 1300-1700 ft MSL have
filled in the majority of the coastal basin. VIS reductions of 3-5SM
in elevated inland valleys (HZ/BR) and down to 0-5SM where clouds
intersect terrain in the IE and surrounding foothills. Scatter out
16-18z, though intermittent SCT-BKN cigs possible after 21z along
the beaches. Low clouds will return to coastal areas 02-04z Mon and
inland areas 07-09Z, with similar bases and vis reductions.



Mountains/Deserts...VFR conditions prevail through this evening with
typical late afternoon S/W winds gusting 15-25 kts (up to 35 kts
through the Banning Pass).

&&

.MARINE...
West-northwest winds expected to gust up to 20 knots in the outer
coastal waters this afternoon. Otherwise, no hazardous marine
conditions are expected through Thursday.

&&

.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...Westerink
AVIATION/MARINE...CO