380
FXUS66 KSGX 031642
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
940 AM PDT Mon Jun 3 2024

.SYNOPSIS...
Temperatures in the valleys, mountains and deserts will trend upward
this week as high pressure builds over the Great Basin. Temperatures
in the coastal zones will be tempered by the cool marine layer.

&&

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

The marine layer was 3300 feet deep this morning, a few hundred feet
shallower than yesterday. As a result, drizzle reports and
precipitation amounts were less widespread than yesterday with 0.01"
of rain reported only at a few stations in the Santa Ana Mountains,
and at Corona and Sage in the Inland Empire.

One final weak upper trough will drift across California tonight,
followed by a building ridge over the Great Basin that will bring
warmer/hotter days Wednesday through Friday. Model trends show the
ridge exerting a greater influence over the Southwest than previous
runs, mainly because the closed upper low that was forecast to be
over northern Baja this week is now projected to be farther
southwest off the coast of southern Baja. Therefore, the heat
influence will be greater over Southwest California, so much so that
the Excessive Heat Watch that is in effect for the high deserts
Wednesday and Thursday will likely need to be expanded to include
the Coachella Valley and the San Diego County deserts, and also
extended into Friday. High Desert highs will range from 97-103, and
Lower Desert highs will range from 108-113.

The mountains will be warmer too, with highs from 80-90. Valley will
also be warmer as the ridge aloft will squashes the marine layer a
few hundred feet. Inland Empire highs will range from 93-97 in the
eastern sections and from 85-93 in the western sections. Areas
within 10 miles of the coast will remain under the influence of the
marine layer which will keep highs coastal highs in the upper 60s at
the beaches but from 75-80 degrees from 5 to 10 miles inland.

Next weekend the long range models show the southern Baja closed low
moving north. The ECMWF transitions this closed low to a weaker open
wave, while the GFS maintains the closed low and shows a greater
chance of isolated convection. These probabilities will become
clearer over the coming days. The weekend will trend cooler as
heights lower ahead of the approaching trough. There should also be
some deepening of the marine layer.

&&

.AVIATION...
031530Z...Coast/Valleys...Low clouds continue to cover the entire
coastal basin with bases 1500-2000 feet MSL with tops to 2800 feet
this morning. Some higher terrain will be obscured in clouds/FG,
with local VIS 3-5SM in the valleys. Scattering and clearing will
occur 17-19Z in the valleys and 18-20Z near the coast, with areas of
BKN clouds continuing at the immediate coast this afternoon. Low
clouds will push ashore after 00Z and locally inland overnight, but
not entirely cover the coastal basin by Tuesday morning. Bases would
be 1000-1500 feet MSL with more vis restrictions where clouds reach
inland overnight.

Mountains/Deserts...Local westerly wind gusts 25-35 kt after 21Z
through mountain passes, desert slopes and into adjacent deserts,
including through/near San Gorgonio Pass with MOD UDDFS.

Regionwide...SCT locally BKN high clouds above 20000 feet MSL today
and tonight.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Watch from Wednesday morning through Thursday
     evening for Apple and Lucerne Valleys.

PZ...None.

&&

$$

PUBLIC...Moede
AVIATION/MARINE...Adams