Hesperia, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

835
FXUS66 KSGX 130400
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
900 PM PDT Sat Jul 12 2025

.SYNOPSIS...
Brief warming for Sunday and Monday. Gradual cooling back to near
average for mid July expected for the middle to the end of next
week. While chances are still low and uncertainty remains, some
confidence is increasing for the potential of monsoonal
thunderstorms over the mountains late next week. 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...

Satellite at 9 PM was showing low clouds along much of the coast.
The 00Z sounding from KNKX showed the marine layer depth to be
around 1500 ft with low clouds expected to make it into the valleys
overnight. Forecast remains on track with no changes made this
evening.

From previous discussion issued at 2 PM July 12...

The dominant upper ridge in control of the region`s weather is
currently displaced just off the California and is also a tad weaker
than it was earlier in the week. The ridge restrengthens and spreads
back overhead Sunday and Monday, leading to a rebound in
temperatures up about 5 degrees warmer than today. The marine layer
depth decreases some with the building ridge, but will still be
around 1500-2000ft deep.

By mid-late Monday, a shortwave trough rounding the upper ridge will
be on the southern periphery, which looks to place it across
northern Baja. While some monsoonal moisture will likely accompany
this shortwave, any convection will likely be limited to the
mountains in northern Mexico. While unlikely, a stray storm over the
extreme southern San Diego County mountains cannot be ruled out. By
Tuesday/Wednesday, this disturbance will have passed but should
leave the ridge weakened and displaced back to the eastern Four
Corners Region. This opens the door for a series of disturbances
Thursday through the end of the week. While model guidance continues
to show a fairly vast range of solutions in the exact placement of
the ridge and corresponding tracks of the aforementioned
disturbances, more ensemble members (notably out of the higher-
resolution ECMWF which were previously more dry in the last several
runs) are starting to coalesce around the chance of diurnal
monsoonal thunderstorms in the mountains possible each afternoon
Thursday-Saturday. Significant uncertainty in timing is muddling the
view here and a few more days of seeing how the pattern evolves is
necessary to say with much confidence who will see, or even if,
thunderstorms occur. There is still good agreement in a gradual
cooldown as a result of this pattern, which has many locations 5 to
10 degrees cooler on Wednesday compared to Monday.

&&

.AVIATION...
130330Z....Coast/Valleys/Foothills...Low clouds linger just off the
coast with bases 1100-1500ft MSL. Clouds will push inland over the
next two hours, reaching up to 20 miles by 11z. Bases may fall a bit
closer to 900-1200ft MSL after 07z with localized VIS reductions for
valleys and terrain down to 3-5SM. CIG expected at KONT and much of
the Inland Empire after 10z with bases closer to 700-900ft MSL.
Clouds clear to the coast by 16-18z, possibly lingering at the
beaches through the afternoon. Clouds develop and push in again
Sunday night after 02z with bases closer to 1500ft MSL.

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

&&

.MARINE...
No hazardous marine conditions 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...CO/Munyan
AVIATION/MARINE...Zuber