Colton, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

975
FXUS66 KSGX 162057
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1257 PM PST Tue Dec 16 2025

.SYNOPSIS...
High pressure aloft and weak offshore flow will bring warming of a
few degrees today with northeast winds gusting to 40 mph near and
below the Cajon Pass through this morning. For coastal areas,
night and morning coastal low clouds and locally dense fog will
continue through Wednesday. Onshore flow will spread cooling of a
few degrees inland on Wednesday followed by warming with weak
offshore flow on Thursday. Onshore flow and weakening high
pressure aloft will spread cooling inland for Friday through
Monday of next week, but with high temperatures remaining as much
as 10 to 15 degrees above average for some inland areas for
Saturday through Monday.

&&

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

Tonight through tomorrow night...

High pressure conditions continue to dominate the region with above
average temperatures in place. Persistent subsidence from this will
result in in the formation of fog developing again along the coastal
areas for tonight. There may also be some areas of patchy dense fog,
especially along the coastal areas. Some of this may penetrate
into the IE. The timing of this is somewhat finicky, although a
consensus of high pres models puts the initiation of this sometime
around 6 pm tonight, and then clearing out for most areas by
tomorrow morning at around 10 AM. Temperatures will be similar
tomorrow for highs, maybe only a smidgen cooler. Fog will likely
form again along the coastal areas and portions of the inland
valleys extending about 5 to 10 miles inland.

Thursday through early next week...

The ridge will continue to build ahead of an approaching major
shortwave trough which will be approaching the region by this
weekend. It will be considerably warmer on Friday as this occurs,
with temperatures running around 20 degrees above average for the
inland valley areas. As the trough continues to advance slowly
eastward, with will help to bring about a cooling trend going into
early next week, with the marine layer beginning to lift with
strengthening onshore flow. Looking a little beyond the forecast,
there is growing confidence with ensemble and deterministic models
alike which show an increasing chance of precipitation across the
region.

&&

.AVIATION...
161615Z...Coast...Low clouds/FG based 200-400 ft MSL with tops to
600-700 ft and vis 1/4-2 SM fluctuating in and out of San Diego
coastal areas and firmly entrenched in northern Orange County.
Scatter out vcnty KSAN by 17Z, 18-19Z vcnty KSNA. Low clouds and fog
to return to coastal airports 01-05Z, with slightly higher cigs/vis
and extending a little farther inland overnight into Wednesday.

Otherwise...Mostly clear skies with unrestricted vis today and
tonight.

&&

.MARINE...
Areas of dense fog will continue this morning. A Marine Weather
Statement contains the details. Otherwise, no additional 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...Dense Fog Advisory from 6 PM this evening to 10 AM PST Wednesday
     for Orange County Coastal Areas-Orange County Inland Areas-
     San Diego County Coastal Areas.

PZ...None.

&&

$$

PUBLIC...Stewey
AVIATION/MARINE...CSP