Area Forecast Discussion
Issued by NWS San Diego, CA

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020
FXUS66 KSGX 182029
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
129 PM PDT Fri Jul 18 2025

.SYNOPSIS...
Showers and thunderstorms will continue across the mountains and
deserts through this evening as pesky marine layer clouds hover
over parts of the coast. Monsoonal activity will decrease on
Saturday with a minor chance of storms being focused in the
mountainous regions. By Sunday into the middle of next week, a
troughing pattern will take hold over the region, leading to dry
weather with temperatures near to below average with marine layer
clouds closer to the coast each morning. This pattern may linger
into later next week as well.

&&

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

Radar imagery shows isolated thunderstorms over the San Bernardino
mts early this afternoon as an area of low pressure over northern
Baja pulls in monsoonal moisture. Storms located near Big Bear and
Lake Arrowhead have produced rain rates over one inch per hour.
Upper level winds remains stronger where adequate shear is
present to aide in pulsating storms. Weaker shear is noted in the
lower levels, where storm motion is fairly stagnant. This will
lead to certain areas seeing localized flooding concerns. Storms
may produce cloud to ground lightning, small hail and gusty winds.
Hi- res models continue to show storm activity lasting until
around 8PM this evening. The low will weaken on Saturday, but some
leftover moisture and instability over the mountains will leave
around a 15-20% chance of thunderstorms. The marine layer will
maintain its presence through the weekend, especially in San Diego
County tonight, building across much of the coast by the weekend.

By Sunday, a trough of low pressure will move into the Pacific
Northwest. This will bring cooler and drier air to California,
helping to push monsoonal moisture further east. Tranquil weather
will return to the region Sunday through at least the middle of
next week. Ensemble guidance shows the trough deepening into
Northern California by the middle of the week. This pattern will
create temperatures near to around 10 degrees below normal with
dry conditions. The marine layer will become deeper during this
time period, with night and morning low clouds moving in for the
coast and adjacent valleys.

&&

.AVIATION...
182030Z....Coast...SCT, locally BKN, low clouds with bases around
1500 feet MSL will return in full after 04Z. Scatter out Saturday
by 17Z.

Valleys/Mountains/Deserts...SCT-BKN clouds 10000-15000 feet. ISO-SCT
TSRA over the mountains, high desert and 20% chance in adjacent
valleys through 02Z, with CU/CB bases 7000-9000 feet MSL, tops to
40000 feet. Erratic wind gusts, strong up/downdrafts, and VIS
restrictions possible with any TSRA. Gradually clearing after 03Z.
CU/CB based at 9000 feet MSL developing into ISO TSRA over mountains
19-00Z Saturday.

&&

.MARINE...
No hazardous marine weather expected through Wednesday.

&&

.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...MM