341
FXUS66 KSGX 010441
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
941 PM PDT Sun Jun 30 2024

.SYNOPSIS...
Hot conditions are expected this week for inland areas, with the
hottest conditions in the deserts. Highs in the deserts will be 10
to 15 degrees above normal Thursday through Sunday with highs in the
valleys 6 to 12 degrees above average Friday and Saturday. The
marine layer will be shallow, where areas near the beaches and
adjacent valleys will see night and morning low clouds most days.

&&

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

Low cloud coverage is expected along much of the coast tonight
and into portions of the western valleys. Low clouds are expected
to clear fairly quickly Monday morning, leaving plenty of sunshine
across the area. Highs on Monday will be a few degrees cooler
than today from the coast to the deserts with an upper level
trough moving east across the Great Basin. Warming is expected in
the deserts by Tuesday as influence from the low weakens. A strong
high pressure system aloft will slowly move towards California
from the Pacific through the work week. The high will eventually
park itself over California by the weekend, causing high
temperatures to soar to well above seasonal normals for inland
locations. Global ensemble guidance is showing the high pressure
system lingering over the West Coast into next week, although
there is some uncertainty in the details regarding the strength
and placement of the high starting Saturday. Even with that
uncertainty, there is enough agreement amongst the guidance to
indicate that the high will stay close enough to continue this
heat wave into at least the beginning of next week.

Moderate to high heat risk for inland areas Wednesday through at
least Sunday will lead to elevated impacts for those outdoors.
Make sure to take frequent breaks if working outside, drink plenty
of water, and be safe and smart while doing outdoor recreation.

From previous discussion issued at 2 PM June 30...

By Wednesday, winds will weaken for mountains and deserts, with a
shallow marine layer within 20 miles of the coast leading to patchy
fog each morning. A large area of high pressure over the Southern
States along with an inverted trough off the coast of northern
Mexico will help feed elevated moisture into the region, which will
lead to a more humid day, especially for the deserts. Confidence on
any storm development is still very low at this time, but we will
continue to monitor.

The aforementioned area of high pressure will grow and expand across
the State from the middle to the end of the week. 850mb temps peak
across SoCal by Friday and Saturday. Hot temperatures are likely for
those away from the coast starting Wednesday into the long holiday
weekend. Triple digit heat is likely for much of the week for those
along and east of I-15 in the Inland Empire, and certain for all
desert regions. Highs near 110 degrees have a 40-70 percent chance
of occurrence across the high desert, with 60-80 percent chance of
highs 115 or greater for the lower deserts by Friday and Saturday.
High temperatures have a moderate to high chance of reaching into
the 90s from areas east of I-5 in OC to east of I-15 in SD Co,
highest chances on Friday and Saturday. This heat wave will even
bring hot temperatures well into the 80s and 90s across the
mountains!

&&

.AVIATION...
010430Z...Coast/Valleys...Areas of low clouds will continue to
develop within 10 miles of the coast through 08Z Mon and eventually
expand up to 20 miles by 12Z Mon. Bases will be 700-1100 ft MSL with
tops to 1400 ft MSL. Local VIS 1-3 miles in BR will occur 08Z-16Z
Mon in the coastal valleys. Most areas will clear 15Z-17Z Mon with
VFR conditions prevailing Mon afternoon. Low clouds will spread
inland earlier Mon evening, with coastal airport CIGs beginning 02Z-
06Z Tue, with a slight increase in bases.

Mountains/Deserts...Mostly clear skies with unrestricted VIS will
prevail through Mon evening. Local west sfc winds with gusts 25-35
kt will continue through 08Z Mon, then again after 23Z Mon, on the
desert slopes and through San Gorgonio Pass.

&&

.MARINE...
No hazardous marine conditions are expected through Friday.

&&

.BEACHES...
A long-period swell of 2-3 feet from 190 degrees with a period of 16-
18 seconds will arrive at SoCal beaches as early as Wednesday
morning, peak Friday and gradually subside next Sunday. This may
lead to elevated surf with breaking wave heights of 6-7 feet, mainly
on exposed south and southwest-facing beaches in Orange County. Rip
current risks will be high the second half of this week.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning from 11 AM Tuesday to 5 AM PDT Monday for
     Apple and Lucerne Valleys.

     Excessive Heat Warning until 5 AM PDT Monday for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass Near
     Banning.

PZ...None.

&&

$$

PUBLIC...CO/APR
AVIATION/MARINE/BEACHES...Maxwell