Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 270404
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
904 PM PDT Tue Mar 26 2024

.SYNOPSIS...
Weak ridging will bring minor warming on Wednesday. This will be
short- lived as a strengthening low pressure system from the north
moves into the area later this week. Out ahead of it, cooling
will take place by Thursday and Friday with windier conditions for
mountain and deserts. Widespread moderate to heavy precipitation
and gusty southwest to west winds are expected over the weekend as
the storm moves through. Drying will slowly occur by early next
week.

&&

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

.EVENING UPDATE...
Areas of low clouds remain banked up against the lower coastal
mountain slopes and adjacent foothills/inland valleys. Elsewhere
skies are mostly clear. The 00Z KNKX sounding shows a 2.4C marine
inversion based near 4900 ft MSL. The marine inversion will become
more shallow overnight with the upper level ridge moving overhead,
reducing the areal coverage of low clouds into Wednesday morning.
This ridge will bring us greater warming Wednesday with high
temperatures as much as 5-10 degrees higher than today, though
still a couple degrees below normal.

Only change to the forecast this evening was to add low pops and
slight chance of showers for some of the mountains Thursday
evening as a weak wave passes by to the north. Hi-res guidance
indicates at least isolated showers. Area of slight chances may
need to be expanded if this holds.

&&

.PREVIOUS DISCUSSION...
Pressure falls will occur on Thursday and Friday as a potent area
of low pressure from the Pacific Northwest moves further down the
West Coast. This will bring cooling and windier conditions for the
area. Gusty winds will occur across the mountains and deserts
there is moderate to high confidence in wind gusts over 40 MPH for
typical wind-prone mountain passes including the San Gorgonio
Pass. Winds west of the mountains will not be as strong with gusts
15-25 MPH. Temperatures on Thursday will be slightly cooler on
Thursday, and noticeably cooler on Friday.

Taking a look at the latest model suite, probabilities increase
for precipitation sometime on Friday evening or Saturday morning.
The rain and mountain snow is coming, just a matter of exactly
when this weekend. A shortwave off the main area of low pressure
will intensify the low this weekend. Bouts of heavy rain and
mountain snow above 6,000 feet are expected, with two main waves
expected.

Late Friday night into Saturday will see one round of
heavier precipitation with another round expected on Sunday as the
trough axis deepens and moves over SoCal. As it does so, it will
be bringing in some colder air behind it, leading to the coolest
day of the week to likely be on Sunday. Highs will stay only in
the 30s and 40s across the mountains and struggle to get to 60
degrees west of the mountains. We will continue to look into the
storm threat as cooler air aloft may be able to trigger isolated
storm activity as with the passing area of low pressure. Snow
levels are still somewhat uncertain, but northern areas above
6,000 feet will likely see the most significant totals. Snow
levels will fall from 6,500 feet late Friday and Saturday to near
5,500-6,000 feet.

Model cluster guidance becomes more widespread in solutions of
the troughs departure, some leaving it linger in the area through
later on Monday or Tuesday. Depending on how this shapes up will
depend on when the cooler wetter weather will depart. NBM POPs
look reasonable with lower elevations drying out by Monday
afternoon. After this, drier and warmer weather looks to occur.

&&

.AVIATION...
270330Z...Coasts/Valleys...Low clouds with bases 2000-3500 FT MSL
will fill in across inland valleys through 07z Wed, reaching the
coast 05z-08z Wed. Bases will lower overnight to 1700-2200 FT MSL.
Scatter out 17-19z Wed.

Mountains...Local terrain obscurations in clouds will occur on the
coastal slopes below 5000 feet MSL through 12-14z Wed.

Deserts...W winds 20-30 kt on desert slopes and locally into
adjacent deserts will occur at times through 08z Wed, with MOD
up/downdrafts and local VIS 3-5 miles in BLDU.

Otherwise, inc high clouds AOA 20,000 FT MSL on Wed.

&&

.MARINE...
Breezy northwest wind gusts up to 20 knots will be possible Thursday
afternoon and evening. Southerly wind gusts over 20 knots will
develop Friday night through Saturday before turning to the west and
diminishing. Periods of moderate to briefly heavy rainfall will be
possible Friday night through Sunday.

&&

.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...SS/APR
AVIATION/MARINE...EA


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