Lake Arrowhead, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

781
FXUS66 KSGX 120847
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
147 AM PDT Sat Jul 12 2025

.SYNOPSIS...
Slightly cooler conditions today followed by a slight rebound in
temperatures for Sunday and Monday. Gradual cooling back to near
average for mid July expected for the middle to the end of next
week, with perhaps some monsoonal moisture spreading into the
region. Night and morning low clouds will spread across the
coastal areas and into the western valleys late each night.

&&

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

This morning, the large upper level high pressure ridge remains
centered roughly over the Southern California Bight. This is
keeping the marine layer at a depth of nearly 2000 ft. Low clouds
have spread up to about 15 miles inland and could spread farther
inland by sunrise. Inland temperatures have been several degrees
above seasonal averages while the coastal areas and western
portions of the inland valleys have been several degrees below
seasonal averages.

The dominant high pressure ridge will remain roughly in place
through early next week but will be somewhat weakened on Monday
and Tuesday by a low-pressure trough to the northwest and a couple
of inverted troughs moving in from the east with southeast flow in
the mid levels. The mid level flow will likely bring some
monsoonal moisture into extreme southwestern CA on Monday. There
may be enough moisture and instability for convection on Monday
afternoon but the probability of occurrence looks very low at this
time. By Tuesday, the high aloft will shift south and east in
response to a low/trough moving inland to the north. This will
likely displace the moisture south and east away from SoCal. The
evolution of this high pressure ridge will keep inland temperatures
several degrees above seasonal averages. Daytime high temperatures
in the lower deserts are expected to remain in the 106-112 degree
range. The high deserts will remain in the 90s to about 105 while
portions of the Inland Empire will be in the mid to upper 90s.
With respect to the synoptic pattern, numerical guidance across
model platforms is consistent through Tuesday although some spread
in the details remains.

Beyond Tuesday, model guidance is less consistent and the spread
among solutions is greater, leading to less confidence in the
details of the forecast. The most likely scenario is for the high
pressure ridge to weaken and be displaced south and east as a
trough of low pressure moves in from the northwest. This will
bring general cooling and a slightly deeper marine layer. Inland
temperatures for Wed through the end of the work-week will be near
or a few degrees above seasonal averages, even in the lower
deserts where daytime high temperatures will be in the 102-108
degree range. There are indications of a return of some monsoonal
moisture for Thursday into next weekend but the probability of
convection is difficult to determine at this point.

&&

.AVIATION...
120900Z....Coast/Valleys...BKN-OVC low clouds 1200-1500 ft MSL
have moved to inland areas, ultimately extending to around 15
miles inland with high terrain obscured in clouds/fog. Increasing
chance for more clearing toward the coast 18-20Z Saturday with TAF
sites clearing 17- 19Z. Clouds will regather tomorrow evening
around 01-02Z and fill back in tomorrow evening, with very little
deviation in cloud base heights from where they are this evening.

Mountains/Deserts...VFR conditions and unrestricted VIS through
this weekend.

&&

.MARINE...
No hazardous marine conditions expected through the middle of next
week.

&&

.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...PG
AVIATION/MARINE...Westerink