259
FXUS66 KSGX 122052
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
152 PM PDT Fri Jul 12 2024

.SYNOPSIS...
There will be a gradual and slow cooling trend through the middle
of next week. Monsoonal moisture will increase for this afternoon into
Saturday, then decrease for Sunday into Monday. There is a slight
chance of showers and thunderstorms for this afternoon and early
evening for the San Bernardino County mountains and deserts with
greater chances for the mountains and deserts for Saturday
afternoon and early evening. Decreasing chances for thunderstorms
for the mountains and deserts on Sunday, then drier through
Wednesday. Night and morning coastal low clouds will continue to
extend inland into the western valleys at times late each night.

&&

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

.SHORT TERM (Today through Sunday)... An increase in monsoonal
like moisture from the Pacific will continue to stream in to
Southern California from the south through this weekend. The
interaction between the large scale ridge of high pressure over
the Four Corners and weak low off the California coast will allow
for this to occur through the weekend, though the peak of moisture
and associated thunderstorm potential will likely occur on
Saturday.

Showers and thunderstorms Friday afternoon and evening will
generally be widely scattered over the mountains and nearby
deserts.

Some elevated convection could occur Saturday morning, but the
bulk of any convective activity will likely be in the afternoon
hours around and after peak heating. The most favored locations
appears to be the mountains of San Bernardino County, where there
is around a 45 percent chance for 0.01 inch or more of rainfall,
around a 25 percent chance for one- quarter inch or more, and a
less than 10 percent chance for one- half inch or more. There is a
15 to 25 percent chance of showers and thunderstorms for the
mountains and deserts for Sunday afternoon.

&&

.LONG TERM...
Drying and slow cooling will continue through the middle of next
week. With the cooling, high temperatures on Wednesday will be a
few degrees above average for the deserts and a few to around 5
degrees below average for the coast, valleys, and mountains with
high temperatures in the lower deserts around 112 and for the
Inland Empire mostly in the 90s.

There is the potential for a greater influx of monsoonal
moisture for late next week depending on the placement of high
pressure over the Great Basin and southwest states into northern
Mexico. Those that extend farther south with the high would have
less potential for an influx of moisture into southwestern
California while those that don`t extend as far south would have
more potential for a greater influx of moisture.

&&

.AVIATION...
122040Z...Coast/Valleys... Low clouds with bases 600-1000 ft MSL and
tops around 1400 ft MSL over the coastal waters and extending
locally inland. Low clouds returning to coastal TAF sites after
13/02Z this evening with similar bases and tops. Areas of fog with
VIS 2-4 miles, locally 1 mile on higher coastal terrain and portions
of the inland valleys late. Confidence in the arrival time of BKN-
OVC low clouds at KSAN this evening per the TAF is moderate-to-high.

Mountains/Deserts...FEW to SCT200 through today. Localized VIS
reductions down to 3SM due to smoke in the San Bernardino Mountains
VCNTY the Vista fire. Periods of northwest winds gusting to 30 kts
in the San Gorgonio Pass through this evening.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 9 PM PDT this evening for Apple and
     Lucerne Valleys-San Gorgonio Pass Near Banning.

     Excessive Heat Warning until 9 PM PDT Saturday for Coachella
     Valley-San Diego County Deserts.

PZ...None.

&&

$$

PUBLIC...Suk/17
AVIATION/MARINE...Small