123
FXUS66 KSGX 120903
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
203 AM PDT Mon Aug 12 2024

.SYNOPSIS...
Monsoonal moisture will decrease through the early part of the
week, with one more day of notable storm chances for portions of
the southern mountains and deserts this afternoon. This will be
followed by dry and seasonal weather through the week as a trough
to the north brings in cooler and drier air. The marine layer
will be deeper with patchy coastal low clouds and fog through the
week as well.

&&

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

Latest satellite imagery shows high clouds from yesterday`s storm
activity dissipating, while low clouds offshore become more
widespread as the marine layer deepens. Coastal areas have the
potential to see these low clouds and fog occur later this
morning. The marine layer will become more established by Tuesday
into the weekend with higher terrain adjacent to the coast
becoming shrouded in patchy fog each morning.

The main story this week will be the influence from a lingering
trough over Northern California. As the trough gains a bit more
momentum today, drier southwest flow aloft will enter the region,
pushing monsoonal air further east. With just enough moisture
left in place, we will see one more day for a notable chance of
thunderstorms. Chances are less than yesterday near 15 percent
across the mountains of Riverside and San Diego counties, possibly
moving into the Anza-Borrego desert in eastern SD Co. Latest hi-
res models support another moisture intrusion along the mountain
spine in northern Baja, with coverage of storms highest per latest
HRRR output.

PWAT ensemble members significantly lower by Tuesday through the
work week as the trough to the north brings in dry southwest flow
off the Pacific. This will keep daytime temperatures close to
average with lower humidity. There will be minimal changes in
daytime highs through Friday, with nighttime temperatures a bit
more comfortable as well.

By Friday into the weekend, a trough along the west coast of
British Columbia will deepen. Ensemble model clusters agree on the
trough becoming stronger by the weekend, but exact placement of
where this sets up within proximity of the West Coast is still
uncertain. Depending on how close this low pressure trough comes
to us in SoCal, will determine how low we can go with
temperatures and how high we reach in wind speeds. NBM paints
highs near to slightly below average by the weekend. Breezier
than normal conditions will occur across mountains and deserts as
well, but exact details are still to be determined. High pressure
off to the east will begin to influence our weather pattern by
early next week, but uncertainty remains on how long it will be
kept at bay.

&&

.AVIATION...
120900Z...Coast/Valleys...Currently patchy low clouds with bases 900-
1100 ft MSL developing along Orange Co. coastal areas but are well
offshore of San Diego Co. due to SCT-BKN clouds at 15-20k ft MSL. As
high clouds dissipate, patchy low clouds will increase slightly in
coverage with a 30-40% chance for CIG impacts at San Diego Co.
coastal sites 12Z-15Z this morning. Low clouds that do come ashore
will clear to the beaches 15Z-17Z. Otherwise, SCT-BKN clouds at or
abv 10k ft MSL through tonight, clearing through Tue morning. More
extensive low clouds with similar bases to tonight moving ashore 05Z-
07Z Tue.

Mountains/Deserts...SCT-BKN clouds with bases at or abv 10,000 ft
MSL through Tue morning. 10-15% chance for ISO TSRA 20Z Mon to 02Z
Tue over mountains and deserts, but majority of activity expected to
stay to S and E of region. Gusty and erratic winds possible near
storms as well as MOD UDDFS. Storms that do develop moving from SE
to NW.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...APR
AVIATION/MARINE...CSP