Heavy precipitation occurred across northern portions of the SGX CWA from December 28-30. Widespread precipitation amounts greater than 1 inch occurred across Orange and San Bernardino Counties, with 2 to 3 feet of snow reported in the San Bernardino County Mountains.
Every event with a place to put it; 12 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SGX wrote it up.
Heavy precipitation occurred across northern portions of the SGX CWA from December 28-30. Widespread precipitation amounts greater than 1 inch occurred across Orange and San Bernardino Counties, with 2 to 3 feet of snow reported in the San Bernardino County Mountains.
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 Dec 27, 2:00 PM PST, 5 hours 40 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
200 PM PST Mon Dec 27 2021
.SYNOPSIS...
A low pressure system from the northwest will bring precipitation
again, including snow in the mountains, along with strong gusty west
winds this afternoon and evening. Additional precipitation is
possible at times from Wednesday through Friday from a closed upper
level low pressure system off the coast of southern California.
Heavy snow will be possible in the mountains from this storm. Well
below average high temperatures will warm slightly late this week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Mostly cloudy skies prevail as precipitation was starting to move
into the area, especially northern Orange County and the western
part of the Inland Empire. The track of the next wave is a little
slower than what the models were showing Sunday, so most of the
precipitation should begin in most areas late this afternoon. The
HRRR and local WRF are showing hourly maximum hourly precip rates
below 1/2" per hour, so debris flow concerns in the burn scars are
minimal for today/tonight. Precipitation amounts should stay
moderate as the models/ensembles have trended downward a bit,
including a bit of a downward trend to the snow in the mountains.
HREFv3 has the probability of greater than 6" of snow in 6 hours
down to 70-80 percent versus 90 percent in yesterday's runs in the
San Bernardino/Riverside County mountains. Overall, 4-8" of snow
looks good for the mountains above about 5000 feet, with the
possibility remaining of over 1" of snow per hour in the heaviest
time period late this afternoon/early this evening. Strong winds
will prevail in the mountains/deserts due to the strong height
gradients aloft and associated 50-55 knot winds at 700 MB. High-
resolution models show gust potential of over 70 MPH locally on the
upper desert mountain slopes late this afternoon and this evening.
Due to the slower track of the system, the San Diego County part of
the winter storm warning was extended to 3 AM Tuesday, but areas
farther north will still expire at midnight tonight.
The big picture continues to be the winter broad deep long-wave
trough over the western US through Fri/Sat followed by some weak
ridging over the weekend as the trough shifts east. Tue should have
a few showers, mostly light, due to the next wave, but the key point
will be the unusually cold high temperatures, with the chance that
all locations west of the mountains and perhaps even in the lower
deserts remaining below 60, with some locations in the far inland
valleys maybe not even reaching 50! Due to cloud cover and ground
moisture, we at least avoid a freeze at lower elevations the next
few nights.
The storm system Wed-Fri from the north will be slower moving,
partly due to the upper low closing off to our west. This will be
accompanied by deep moisture, with saturation at times possibly
approaching/reaching 500 MB. Timing of the precipitation is still
uncertain, but there is the potential of an inch or more of rainfall
Wed-Fri near the coast (best chances Wed-Thu). Orographics might not
be as good as with previous systems in the mountains, but ENS is
showing a lot of members with heavy snowfall in the San Bernardino
Mountains, specifically 13" on average among the members 18Z Wed-18Z
Thu in the grid box containing Big Bear, and since that includes
some lower elevations, that is a bit conservative. A few locations
above about 7500 feet could get 2-3 feet of snow Wed-Fri. The
atmosphere does warm some, with 700 MB temps rising to around
-5 C by Thu, so snow levels should be a little higher, but not high
enough to preclude snow above about 5500-6000 feet. The closed low
should go inland around Fri, but the track will determine what
happens with our precipitation then, with a more southerly track in
northern Baja meaning less here but a more northerly track across
SoCal could prolong signification precipitation.
Next week has a lot of uncertainty with GEFS solutions generally
showing more troughing off the coast which would result in more
precipitation over the West Coast, including SoCal, and ENS
solutions showing more of less zonal flow and mostly drier weather.
Cluster analysis shows about 50/50 odds for either solution.
&&
.AVIATION...
272100Z...SCT-BKN030-050 through 23Z with isolated -SHRA. Clouds
thickening and lowering to BKN-OVC020-030 between 23Z-09Z with more
widespread showers moving in from the northwest. CIGS down to 015
and vis lowering to 2-5 miles in the heaviest showers tonight.
Mountain slopes becoming obscured in clouds/fog/pcpn tonight. W-NW
winds 25-35 kt in the mtns and desert slopes with gusts to 60 kt and
moderate to strong up/downdrafts and LLWS.
Showers ending most areas tonight except isolated showers Tuesday in
the mountains and in San Diego County. Mountain occasionally
obscured in clouds and fog Tuesday.
&&
.MARINE...
A Gale Warning is in effect through 4 PM Tuesday. West winds
increasing to 20-30 kt with gusts to 35 kt this afternoon and
continuing tonight and Tuesday. The strongest near-gale force winds
will occur tonight, decreasing a bit on Tuesday but remaining at
Small Craft Advisory levels through mid-afternoon. Scattered showers
through Tuesday, most widespread tonight.
&&
.HYDROLOGY...
Precipitation will increase from northwest to southeast late this
afternoon, with a little bit of a delay in timing compared with
previous forecasts. Precipitation should peak this evening then
decrease from the northwest overnight. Rainfall is expected to range
from 0.2 to 0.3 inch near the coast, to 1 to 1.5 inch in the
mountains with one-tenth inch or less in the deserts. Snow levels
will rise to 4500 to 5000 feet in the afternoon, then fall to 3500
to 4000 feet late tonight. This system will be moving fairly quickly
but could locally produce brief rainfall rates of 0.25 to 0.45 inch
per hour.
An upper level low pressure system off the coast of southern
California will likely bring additional precipitation Wednesday
through Friday. Confidence remains lower with timing and amounts
given uncertainties in the track of this upper low, but amounts
could be substantial, with more than an inch near the coast likely.
The greatest potential of greater precipitation amounts would be for
Wednesday into Thursday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning until midnight PST tonight for Riverside
County Mountains-San Bernardino County Mountains.
Winter Storm Warning until 3 AM PST Tuesday for San Diego County
Mountains.
High Wind Warning until 3 AM PST Tuesday for Apple and Lucerne
Valleys-Coachella Valley-San Diego County Deserts-San
Gorgonio Pass Near Banning.
PZ...Gale Warning until 4 PM 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/HYDROLOGY...Maxwell
AVIATION/MARINE...MoedeThe San Diego radar (KNKX), 28 km away, was scanning. The volume nearest the first event began at 07:59 UTC.
5 high wind, 5 heavy snow, 2 heavy rain, 1 flood, 1 flash flood, 1 dense fog, 1 astronomical low tide. Local standard time, as filed.
Wind gust of 73 mph reported at Volcan Mountain.
Wind gust of 63 mph reported at Harrison Peak.
Widespread rainfall reports of 2 to 5 inches, locally higher across Orange County through the duration of the event.
Widespread rainfall reports of 2 to 5 inches, locally higher across San Bernardino County through the duration of the event.
Department of Highways reported widespread snow amounts of 4 to 9 inches across the San Bernardino Mountains on the evening of December 29. Rime icing was reported for 24 to 30 hours and snow water equivalent of 0.5 to 0.75 inch. Numerous trees and powerlines down at the following locations:
Powerline down in roadway at 21622 Sawpit Canyon Road.|Trees and powerlines reported down on Highway 189 with vehicles trapped near Strawberry Peak.|Downed trees blocking Kuffel Canyon Road in both directions at Highway 18.|Downed tree blocking road on La Casita Drive.|Downed powerline on Sugar Cone Lane.|Downed powerline on Lake Forest Road.|Live wire down on Highway 189 on roadway to Blue Jay. Area was cutoff at Highway 189.|Live wire down on West Victoria Court on vehicle.|Downed tree on Oakmount Lane which took out two powerlines.|Downed powerline on Oak Road. Numerous reports of power outages and downed powerlines.|Downed tree covered in snow on Ocean View Drive and City Creek Road.|Downed powerline on Valley Ridge Drive and Wilderness Road.|Downed tree on Meadow Brook Drive and Meacham Drive.|Downed power pole and lines on Rim of the World Drive at Highway 330.|Downed trees and powerlines in Running Springs.|Tree fell on wires on Nob Hill Drive.|Downed tree on Oak Glen Drive and Wild Oak Drive, so plow was unable to plow road.|Downed powerlines on Walnut Hills Drive and Spyglass Drive, and vehicles are driving on powerlines.|Downed powerline on Pioneer Road.
Mt Baldy Ski Area in San Bernardino County reported snow of 24 to 36 inches Top of the Notch 7800 to 8300 feet. Most of the snow occurred on December 30. Nearest gauge indicated 4 inches of water equivalent.
Trained spotter reported 11.5 inches of snow in Wrightwood at 6275 feet.
County Official reported 10 inches of new in Wrightwood at 5900 feet.
County official reported 14 inches of snow at the end of Baldy Road at 6400 feet. Report of Mt Baldy Road closed at Ice House Canyon with 15 inches of snow reported. 2.3 inches of snow water equivalent.
Water up over the curbs and onto the sidewalks all over Old Town Seal Beach. 1.58 inch of rain since noon Wednesday.
Debris flow reported 1 mile NNE Crestline. The Department of Highways reported boulders in northbound lanes of SR138 / Old Mill Road.
Dense fog with a visibility of 1/8 mile reported 6 SE Lucerne Valley.
Whitewater RAWS reported a peak wind gust of 68 mph.
Whitewater South reported a peak wind gust of 61 mph.
Whitewater (015SCE) reported a peak wind gust of 64 mph.
Wind gust of 75 mph reported at Toro Peak.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, December 2021
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: 999275, 999276, 999271, 999272, 999257, 999269, 999264, 999262, 999261, 997229, 997231, 999267, 999278, 999280, 999279, 999277.