After a powerful winter storm brought historic amounts of snow to the mountains in Southern California, an avalanche on the north-facing slopes of Mount San Jacinto in Riverside County was observed by nearby travelers. Three feet of snow had fallen at elevations near 8500 feet on the mountain.
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The episode as NWS SGX wrote it up.
After a powerful winter storm brought historic amounts of snow to the mountains in Southern California, an avalanche on the north-facing slopes of Mount San Jacinto in Riverside County was observed by nearby travelers. Three feet of snow had fallen at elevations near 8500 feet on the mountain.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Diego, CA wrote its last area forecast discussion before the first event at Feb 27, 4:45 AM PST, 4 hours 45 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
445 AM PST Mon Feb 27 2023
.SYNOPSIS...
A broad trough over the West will bring periods of light to moderate
precipitation today and Tuesday. A stronger disturbance will bring
more widespread and heavier rain and mountain snow Tuesday night and
Wednesday. Dry and slightly warmer weather is forecast Thursday
through Saturday.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
* Winter Weather Advisory for the mountains today and Tuesday
* Winter Storm Watch for the mountains Tuesday night through
Wednesday evening
It was cold last night in the wake of the departing cold upper
trough. Here's a sampling of the minimum temperatures through 4 AM.
Ontario 39, Temecula 32, San Juan Capistrano 35, Rancho Bernardo
38, Ramona 30, and the San Diego Airport 45.
In the mountains, Big Bear was 10, Wrightwood 23 and Julian 28.
In the deserts, Palm Springs 42, Thermal 36F, Borrego 34F, and
Victorville 34.
Radar detected a few light echos over the slopes of the San
Bernardino mountains and parts of Orange County last night which had
ended as of 4 AM. The morning will be generally dry, then light rain
will increase in coverage and move into San Bernardino and Orange
County through midday. The rain will then spread south into
Riverside and San Diego Counties this afternoon and evening. Highest
precip amounts will be on the southwest facing slopes of the San
Bernardino Mountains, with lighter amounts farther south in the
Inland Empire and San Diego County. The light rain and mountain snow
will continue tonight, then taper off from north to south Tuesday.
Winter Weather Advisories are in effect for the mountains with this
first shortwave.
After a brief break on Tuesday afternoon, a stronger shortwave will
bring more significant weather impacts, with heavier rain, mountain
snow and strong winds Tuesday night through Wednesday. Winter Storm
Watches are in effect in the mountains with this second shortwave.
High-resolution models project from 0.33" to 0.75" of rain west of
the mountains, and from 1-2" on the west and southwest facing
mountain slopes from orographically enhanced precipitation rates.
The deserts will see 0.01" to 0.25".
Snow levels will be from 3500-4500 feet with several inches of snow
between 4,000-6,000 feet, and perhaps over 1 foot in some mountain
locations above 6,000 feet.
On Wednesday night the trough moves east and the precipitation will
come to an end. Dry northwest flow follows Thursday through Saturday
with minor warming. Highs Friday and Saturday will actually get
above 60 west of the mountains, and above 70 in the lower deserts,
something we haven't seen since last Tuesday, Feb 21st.
&&
.AVIATION...
271030Z...SCT-BKN clouds with bases 3000-5000 feet MSL will continue
today. A band of -SHRA will move through the region (except deserts)
from northwest to southeast after 21-05Z this afternoon and eve.
Cloud bases would lower briefly to 2500 feet MSL and vis to 3-5SM in
SHRA. Another band of -SHRA will pass through with similar effect
on clouds/vis 08-16Z Tuesday.
Winds will increase today after 21Z over the mountains and deserts
with sfc gusts 30-40 kts with isolated gusts to 50 kts along the
wind prone desert slopes. These winds will continue through Tuesday
morning.
&&
.MARINE...
Winds will strengthen and seas will build late Tuesday, leading to
hazardous boating conditions Tuesday night through Wednesday night.
A few hours of gales and very hazardous seas are likely late
Wednesday. No hazardous marine conditions are expected today through
Tuesday, and Thursday through Friday. Check the Coastal Waters
Forecast for details and stay tuned for hazard information.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Weather Advisory from noon today to 4 PM Tuesday for
San Bernardino County Mountains.
Winter Storm Watch from Tuesday afternoon through Wednesday
afternoon for San Bernardino County Mountains.
Winter Weather Advisory from 4 PM this afternoon to 4 PM
Tuesday for Riverside County Mountains-San Diego County
Mountains.
Winter Storm Watch from Tuesday afternoon through Wednesday
evening for Riverside County Mountains-San Diego County
Mountains.
PZ...None.
&&
PUBLIC...Moede
AVIATION/MARINE...MMThe national radar mosaic for the moment the first event began.
1 avalanche. Local standard time, as filed.
An avalanche on Mount San Jacinto was captured in photos and video by nearby travelers, which were then shared by the Riverside County Mountain Rescue Organization. No other specific impacts are known at this time.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2023Every state in 2023This day in weather historyWarnings in California, February 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1080421.