King, California Weather Forecast Discussion

989
FXUS66 KSGX 260438
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
938 PM PDT Thu Sep 25 2025
.SYNOPSIS...
The low pressure system that brought showers and thunderstorms to
Northern California is moving toward Southern California,
increasing winds, lowering temperatures, deepening the marine
layer and bringing the potential for showers and thunderstorms
Friday through Sunday. Early fall-like temperatures will stick
around thereafter with calmer weather.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Temperatures today were several degrees lower than yesterday in
all areas. The marine layer is deepening, now at about 2500 ft
with low clouds already reaching the coastal mtn slopes in San
Diego County. It`s likely that within a few more hours, low clouds
will cover all areas west of the mtns. If the saturated layer
under the marine layer inversion gets thick enough, then we could
see drizzle in much of the coastal areas and valleys. Local high-
resolution models indicate that this will be the case. The
westerly winds are strengthening and the wind-prone locations at
the eastern end of the Banning Pass are reporting wind gusts of
35-50 mph this hour. Winds will remain relatively strong through
Friday morning.
From previous discussion...
High resolution models introduce a slight chance for a few
thunderstorms over the mountains Friday afternoon. As the low
slowly shifts to the southeast, there will be greater easterly
flow aloft and confidence increases Saturday morning for scattered
thunderstorms drifting westward into the desert slopes and
mountains. With daytime convection, moderate confidence for
scattered thunderstorms across the mountains and deserts with a
30-40% chance a few storms drifting into the Inland Empire and a
20-30% chance for a storm or two reaching into the inland valleys
of San Diego County. While the upper level vorticity maximum will
provide adequate support for scattered thunderstorms, CAPE values
will likely remain below 1000 J/kg, supporting mainly sub-severe
storms. PWAT values will reach up to 1.50 inches Saturday
afternoon, yielding a moderate chance for localized flooding
associated with rainfall rates locally over 1 inch/hr. Storm
activity should wrap up quickly after sunset Saturday with only a
slight chance for an isolated storm Sunday over the mountains.
Next week, consistent upper-level westerly flow will keep
temperatures near to slightly below average with only slight
variations in temperatures.
&&
.AVIATION...
260330Z....Coasts/Valleys...Low clouds based 1000-1800 feet MSL
currently spreading inland over San Diego County. Clouds will
quickly fill the coastal basin through 09z. Cigs may rise slightly
overnight. However, patchy -DZ expected 08-17Z, especially along the
coast, which will intermittently reduce cigs/vis. FG along the
coastal slopes of the mtns where clouds intersect terrain. Clouds
begin to retreat toward the coast 16-17Z, but SCT-BKN low clouds
based 1500-2500 ft MSL will likely stick around all day for coasts
and western valleys up to 20 miles inland. Expecting clouds to fill
up the coastal basin again Friday night.
Mountains/Deserts...Increasing west winds 25-40 kts across mtn
passes and desert slopes until 12Z. 20% chance of ISO TSRA with
storm tops to 30K ft across the mountain areas and deserts north of
Big Bear on Friday afternoon.
&&
.MARINE...
No hazardous marine conditions are expected through Monday.
&&
.BEACHES...
Long period south swell from Hurricane Narda will arrive this
weekend. Swell of 5-6 feet with a period of 14-15 seconds will
produce high surf and strong rip currents, especially for south
facing beaches, Sunday through Tuesday. Surf heights will be highest
along south-facing beaches with heights 5 to 7 feet; sets 8 to 10
feet possible in Orange County. Coastal flooding and erosion are
possible, especially during high tides.
&&
.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...PG
AVIATION/MARINE/BEACHES...KW

NWS SGX Office Area Forecast Discussion