441
FXUS66 KSGX 240415
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
915 PM PDT Sun Jun 23 2024

.SYNOPSIS...
Temperatures west of the mountains will gradually decrease into
next week, but the heat will remain through Thursday in the
deserts. Slight chances of isolated showers and thunderstorms
remain over the San Bernardino and Riverside mountains, locally
into the High Desert Monday afternoon. Drier and warm conditions
continue later in the week.

&&

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

.Evening Update...
Elevated convection made a small appearance this afternoon across
our forecast area with rainfall seen near Toro Peak and other
spots across the high desert. Moisture and instability look to
remain in place, though not as prevalent by Monday afternoon.
This matches hi-res model thinking of minimal activity expected
over the mountains and deserts for the period, with highest
chances being near the higher peaks.

Highs were once again well above average today along with some
sweltering humidity. San Diego reached a high of 84 degrees this
afternoon. The last time San Diego went into the 80s was back in
November. Heat advisories for valleys west of the mountains are
now expired as slightly cooler air will bring temperatures as well
as humidity down, though warm temperatures will remain for much of
this week.

.Previous Discussion (203 PM Sunday)...

Model guidance is showing the moisture over Southern California
very slowly decreasing into Wednesday. Guidance is also indicating
the atmosphere will slowly stabilize into Wednesday as drier air
moves in aloft in more westerly flow. Current forecast leaves
chances for isolated showers and thunderstorms in the San
Bernardino and Riverside mountains into portions of the High
Desert Monday afternoon. High resolution models are also very
bullish about shower and thunderstorm development Monday, but
enough moisture and lingering instability will be present for an
isolated shower or thunderstorm to develop.

A Pacific trough will slowly move into the Pacific
Northwest this week, weakening the ridge currently over the
Southwest. As a result temperatures west of the mountains will fall
a couple degrees each day Monday through Thursday. By Thursday, even
the deserts will see a few degrees of cooling. As the trough
approaches and the influence from the ridge weakens, the marine
layer will be able to rebuild. By mid-week night and morning low
clouds should return to the coast, locally into the western valleys.

&&

.AVIATION...
240400Z...Coast/Valleys...Occasional SCT local BKN clouds at/above
12000 feet MSL will continue through Mon evening. Only patchy mostly
SCT low clouds with bases 800-1100 ft MSL will occur 08Z-17Z Mon
with less than a 20 percent chance of a CIG at any coastal airport.
Most VIS will remain unrestricted through Mon afternoon. Areas of
BKN low clouds and patchy fog could develop along the San Diego
County coast after 04Z Tue.

Mountains/Deserts...Occasional SCT local BKN clouds at/above 10000
feet MSL will continue through Mon evening with mostly unrestricted
VIS. There is a 20 percent chance of TSRA over the mountains Mon
afternoon, with CB tops to 30000 ft MSL possible, along with local
strong up/downdrafts.

&&

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

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 8 PM PDT Thursday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

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