822
FXUS66 KSGX 211145
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
445 AM PDT Fri Jun 21 2024

.SYNOPSIS...
Hot today and then even hotter on Saturday as high pressure builds
over the Four Corners region. A surge of monsoon moisture on Sunday
will bring higher humidity and a slight chance for thunderstorms.
Hot weather will continue in the valleys, mountains and deserts
through Thursday with high pressure anchored over the desert
southwest. A shallow marine layer will keep coastal highs in the 70s
and 80s.

&&

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

A dome of hot air associated with a massive area of high pressure
over Texas will steadily drift west toward the Southwestern U.S.
this weekend, then remain nearly stationary over the Four Corner
region through most of next week. Today will be hotter than
yesterday, and Saturday will be an even hotter day when Heat
Advisories are in effect for the mountains and valleys. In the High
Deserts, an Excessive Heat Watch is in effect Saturday and Sunday.
In the Lower Deserts, an Excessive Heat Watch is in effect Saturday
through Thursday with the heat dome stagnating over the eastern
California deserts. Highs in the Coachella Valley and the San Diego
County Deserts will range from 110-116.

On Sunday a surge of mid-level monsoon moisture will bring higher
humidity which will make it harder to keep cool during any outdoor
activities. Additionally, a weak easterly wave in the southeast flow
around the Four Corners high will track across southern California.
This shortwave interacting with the monsoonal moisture will
destabilize the atmosphere sufficiently for possible showers and
thunderstorms Sunday.

&&

.AVIATION...
210945Z...Coast/Valleys...Low clouds increasing in coverage and
extending locally into the valleys at this hour. Bases are 1100-1300
ft MSL with tops to 1700 ft MSL with local VIS 3-5 miles in BR over
higher coastal terrain and western portions of the valleys. CIG
impacts likely at KSAN and KCRQ until about 16Z, then at KSNA 11Z to
15Z. CIG and/or VIS impacts not expected at KONT or KSBD. Clearing
to the coast will occur 15Z-18Z, with only patchy low clouds
returning to the coast after 03Z Sat.

Mountains/Deserts...Mostly clear with unrestricted VIS through Fri
evening. West winds with gusts 20-35 kt through San Gorgonio Pass
and other favored locations on the desert slopes and into the
deserts will continue to weaken through Friday.

.MARINE...
A system moving by to the south will bring a small chance (less than
20%) of precipitation and a 10% or less chance of lightning Saturday
night through Sunday. Otherwise, no hazardous marine conditions are
expected through next Wednesday. See the Marine Weather Statement
for more information on the potential for thunderstorms.

&&

.BEACHES...
There is a slight chance of a thunderstorm Saturday night through
Sunday which could produce cloud-to-ground/cloud-to-water lightning
strikes. Chances of a lightning strike near any particular beach are
currently 10 percent or less Saturday night and Sunday.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 10 AM Saturday to 8 PM PDT Sunday for Orange
     County Inland Areas-San Bernardino and Riverside County
     Valleys-The Inland Empire.

     Heat Advisory from 10 AM to 8 PM PDT Saturday for Riverside
     County Mountains-San Bernardino County Mountains-San Diego
     County Mountains-San Diego County Valleys.

     Excessive Heat Watch from Saturday morning through Sunday
     evening for Apple and Lucerne Valleys.

     Excessive Heat Watch from Saturday morning through Thursday
     evening for Coachella Valley-San Diego County Deserts-San
     Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC...Moede
AVIATION/MARINE...PG