967
FXUS66 KSGX 052029
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
129 PM PDT Tue Aug 5 2025

.SYNOPSIS...
High pressure will expand westward, leading to warmer weather
across the region through Friday. Increased heat risk will be felt
for many areas away from the coastal regions with triple digit
heat for inland valley and desert areas. This period will also be
accompanied by a greater chance of foggy conditions closer to the
coast and adjacent valleys. Most of Southern California will see
temperatures closer to average by the weekend into next week as
the area of high pressure weakens.

&&

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

A near 600dm area of high pressure over New Mexico will continue
to gain strength Wednesday into Thursday, expanding westward over
Southern California. This will lead to 850mb temperatures to near
30C, prompting temperatures to rise near 5 to 10 degrees above
normal. The peak of the heat over the region will occur on
Thursday across the region. NBM probabilities are moderate to
high in seeing temperatures reach 105 degrees in central parts of
the Inland Empire on Thursday and Friday and 115 on Thursday in
the lower deserts. Please take precautions to beat the heat, such
as staying in air conditioned places, taking breaks if having to
work outside, and limiting outdoor recreation. As the high moves
over the region, the marine layer will become shallower, leading
to greater chances of fog for coastal areas and adjacent valleys
over the next couple of mornings with visibility near one quarter
of a mile at times. By Friday and Saturday, models show the
placement of the high may be able to funnel low level monsoonal
moisture into the lower deserts. Though this has a minute chance
to bring any precipitation, an increase in humidity will make the
heat feel even more oppressive as low temperatures in the lower
desert will only lower from 80 to 90 degrees.

The area of high pressure is expected to retreat further to the
east and weaken over the region by the weekend. This will lead to
temperatures lowering back to seasonal averages with a deeper
marine layer, though desert areas may see highs lower only a few
degrees. Model ensemble guidance points to a growing ridge over
the Pacific Northwest as the ridge over the Desert Southwest
maintains its weaker strength, keeping us in a quiet weather
pattern for the first half of next week. Differences in the
forecast trends start to arise by the latter half of next week as
as the interactions with the high near our area and a potential
trough to the north lead to greater uncertainty.

&&

.AVIATION...
052030Z....Coasts/Western Valleys...Low clouds based 500-800 feet
MSL, tops to 1100 feet, and vis 3-5SM, 0-2SM over higher coastal
terrain and western valleys, will gradually redevelop after 06Z
into Wednesday morning. Scatter out Wednesday 15-16Z.

.Inland Valleys/Mountains/Deserts...VFR conditions prevail through
Wednesday morning.

Smoke from area fires, mostly the Gifford Fire in Santa Barbara
County, will continue to reduce vis especially at or above 10000
feet MSL. Surface conditions hazy but still VFR.

&&

.MARINE...
No hazardous marine 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...Heat Advisory from 10 AM Wednesday to 8 PM PDT Friday for Orange
     County Inland Areas-Riverside County Mountains-San
     Bernardino County Mountains-San Bernardino and Riverside
     County Valleys-The Inland Empire-San Diego County Mountains-
     San Diego County Valleys-Santa Ana Mountains and Foothills.

     Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Friday for
     Coachella Valley-San Diego County Deserts-San Gorgonio Pass
     near Banning.

PZ...None.

&&

$$

PUBLIC...APR
AVIATION/MARINE...MM