Flash Flood and Damaging Winds in California, March 3 to 7, 2025

Area Forecast Discussion
National Weather Service San Diego CA
250 AM PST Mon Mar 3 2025

.SYNOPSIS...
Cool and unsettled weather pattern is expected through much of
this week. Periods of gusty westerly winds expected through this
evening along with periods of light to locally moderate
precipitation. Snow levels will fall to 3500 to 4000 ft later this
morning. Tuesday will be dry and slightly warmer. Additional
chances of precipitation are expected Wednesday through Friday
and again early next week along with periods of gusty winds in the
mountains and deserts.

&&

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

Scattered light showers persist this morning, mainly over the
eastern San Bernardino Mountains as well as across San Diego
County for the mountains westward. Showers remain light with
rainfall rates below one-tenth inch per hour. Showers will taper
off from north to south through the day, ending by the late
afternoon. Additional rainfall amounts where showers occur will
range anywhere from a couple hundredths of an inch to around 0.15
inch, with isolated amounts up to 0.40" on the west slopes of the
San Diego County mountains. Show levels will fall to 3200-3700 ft
this morning, though by that point any additional snow will
mainly be confined to the San Diego County mountains. There's
around a 60% chance of at least 1" of snow on I-8 near Pine
Valley which could impact travel later this morning, changing back
over to rain by the early afternoon as snow levels begin to rise.
Otherwise gusty west winds will continue across the mountains and
deserts today with local gusts to 50 mph below the passes. High
temperatures will be around 7-15 degrees below normal today.
Warmer and drier Tuesday as weak ridging moves over the area with
highs a couple degrees below normal.

Ensembles remain in generally good agreement with the arrival of
another upper level trough late Wednesday through Friday, bringing
a return of precipitation and gusty onshore winds in the mountains
and deserts. This is still forecast to be the wettest system of
the week as both the EPS and GEFS show a weak Atmospheric River
moving into Southern California Wednesday evening with ensemble
mean IVT around 300 kg/m/s. This will result in more widespread
and heavier precipitation Wednesday night through Thursday
morning, with scattered showers following for late Thursday
morning through Friday afternoon as a second short wave moves
through the mean trough. There are some differences in the depth
and timing of the main trough, the former resulting in spread in
precipitation amounts. In general there is a 60-75% chance of at
least 0.50" for the coasts and valleys, and a 20-40% chance of at
least 1". For the mountains, there is a 40-80% chance of at least
1", and a 10-35% chance of at least 2", with the highest
probabilities on the south slopes of the San Bernardino mountains.
For the high deserts, there is a 20-45% chance of at least 0.25",
and around a 15-25% chance in the low deserts. Snow levels will
be upwards of 7000 ft at the onset of precipitation Wednesday
afternoon/evening, quickly falling to around 4000-4500 ft by
Thursday morning, and as low as 3500-4000 ft on Friday morning.
For the 5500-6500 ft level, there is around a 65-75% chance of at
least 6" of snow and a 15-30% chance of at least 10". There is
once again potential for snow along I-15 and I-8 through the
mountains.

Warmer and drier weather follows for next weekend with high
temperatures near seasonal averages. Ensembles are in good
agreement with the arrival of another upper trough early next
week, though they still struggle with the timing with the overall
trend being slower. A few members bring precipitation in as early
as Sunday night, though the majority have something closer to
Monday morning or afternoon. There is considerable spread in
precipitation amounts with this system, but overall looks like it
will result in more beneficial rain and mountain snow.

&&

.AVIATION...
031030Z...Coast/Valleys/Mountains...SCT clouds vcnty
KSNA and KONT with BKN clouds with bases 3500-4500 feet MSL with
tops to 7000 feet with SCT -SHRA mainly in San Diego County through
19Z. Coastal slopes locally obscured in -SHRA/FG up to crests.
Scatter out to continue vcnty KSNA and KONT along with KSAN and KCRQ
after 19Z. Breezy west-northwest winds with areas gusting to 20-30
kt, especially near the immediate coast and over higher terrain
leading to MOD-STG up/downdrafts in lee of mountain ridges. Winds
gradually diminish after 02Z.

Deserts...SCT to locally BKN clouds near mountains above 6000 feet
MSL. Breezy west-northwest winds with areas gusting to 30-40 kt,
strongest through 01Z near desert mountain slopes, leading to MOD-
STG up/downdrafts and occasional rotors near mountains and areas of
reduced vis 3-5SM in BLDU. Winds diminish after 02Z.

&&

.MARINE...
Northwest winds of 20-25 knots with some gusts exceeding 30 knots
and seas 9-14 feet will lead to hazardous boating conditions today
and tonight. Winds and seas will gradually subside tonight. The
Small Craft Advisory contains more details. Stronger westerly winds
and higher seas will arrive Wednesday night and continue into Friday
morning, generating hazardous boating conditions.

&&

.BEACHES...
A long-period swell from the west-northwest will bring high surf and
dangerous swimming conditions today into tonight. Surf of 4-8 feet
with sets up to 10 feet can be expected, with highest surf in
southern San Diego County. Surf will gradually subside tonight. The
High Surf Advisory contains more details. Additional high surf is
likely Thursday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory until 10 PM PST this evening for Orange
     County Coastal Areas-San Diego County Coastal Areas.

     Winter Weather Advisory until 10 AM PST this morning for
     Riverside County Mountains-San Bernardino County Mountains.

     Wind Advisory until 10 PM PST this evening for Apple and Lucerne
     Valleys-San Diego County Deserts-San Diego County Mountains-
     San Gorgonio Pass near Banning.

     Winter Weather Advisory until noon PST today for San Diego
     County Mountains.

PZ...Small Craft Advisory until 2 AM PST Tuesday for Coastal Waters
     from San Mateo Point to the Mexican Border and out to 30 nm-
     Waters from San Mateo Point to the Mexican Border Extending
     30 to 60 nm out including San Clemente Island.

&&

PUBLIC...SS
AVIATION/MARINE/BEACHES...MM