A fast-moving storm system moved from north to south across Southern California during the evening hours on December 27th and moved out on the morning of December 28th. Moderate to heavy precipitation was observed at many locations from the mountains to the coast, with some reports of rocks falling onto Highway 38 in the San Bernardino County Mountains.
Every event with a place to put it; 2 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.
A fast-moving storm system moved from north to south across Southern California during the evening hours on December 27th and moved out on the morning of December 28th. Moderate to heavy precipitation was observed at many locations from the mountains to the coast, with some reports of rocks falling onto Highway 38 in the San Bernardino County Mountains. High winds also occurred across multiple mountain and desert foothill locations with this storm.
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, 9:11 AM PST, 2 hours 49 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
911 AM PST Tue Dec 27 2022
.SYNOPSIS...
It will be cooler today under extensive cloudiness. A band of
light to moderate rain will move down the coast this evening and
overnight. High snow levels will keep this mostly rain for the
mountain communities. After this storm exits the region Wednesday
morning, most locations look to stay dry Wednesday afternoon
through early Saturday morning. The next storm will arrive
Saturday afternoon, bringing another round of precipitation with
the bulk of the rainfall likely occurring Saturday night through
Sunday morning. This storm could be a bit more impactful, with
more snow in the mountains, and locally heavier rainfall rates
late Saturday into early on New Years Day. Another storm system
could arrive Jan 3-4 for additional precipitation.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Update:
Extensive mid-high level cloudiness covers Southern california
this morning with some lower clouds near the coast. This is ahead
of the first storm system with rain moving south down the coast.
The rain lies north of Point Conception this morning and looks to
arrive into our northwest service area/Orange County at around
sunset with the band of light to moderate rain moving southward
overnight.
Latest HRRR shows total rainfall amounts with this system of
0.30-0.60" for areas along and west of the mountains and amounts
up to ~1" over Palomar Mountain and Mt. San Jacinto. Lower deserts
looks completely rain-shadowed and only 0.10" or less for the high
desert. These amounts are similar to our going forecast. The snow
level will be above 9,000 feet during the bulk of the
precipitation, lowering to 6500-7500 feet on the back end, so
not looking like any accumulating snowfall for the mountain
communities.
The rain will come mostly at dark tonight and early Wednesday
morning as the storm system is fast moving, so much of Wednesday-
Thursday-Friday now look dry for most areas. The next system over
New Years weekend will also be fast moving as well and may mostly
come at night too.
Previous Discussion:
Thickening high clouds are overspreading the region this morning
as an Atmospheric River pushes into northern CA. A patch of
stratus/fog was visible on satellite imagery earlier in the
evening, but if any remains it is obscured by the high clouds.
Given the coverage of high clouds and lowering dew points along
the coast with no eddy in sight, chances of any fog along the
coast this morning are diminishing. Expect some low cloud
development later this morning into the afternoon as the first
storm approaches.
Latest ensemble and deterministic model guidance has trended
towards lighter precipitation amounts for the first system later
today into Wednesday as the AR moves south and weakens. The
wettest members of the GEFS and ECE, which once upon a time had
amounts of 2" or more along the coast, are long gone. Hi-res
guidance suggests rainfall rates of 0.20" per hour or less for
coastal and valley areas, slightly higher along the upper west
facing coastal slopes where some orographic lift will occur. It's
quite unfortunate that with precipitable water forecast to be
around 1.5 inches that we lack forcing to generate more rainfall.
Nevertheless, we should still see decent totals - around
0.50-0.75" for the coasts/valleys, 0.75-1.25" for the mountains,
0.15-0.30" for the high deserts, and around 0.10" or less in the
lower deserts. The bulk of the precipitation will fall overnight.
Snow levels begin around 10,000 ft this evening, lowering to
around 6500-7500 ft behind the weak front as precipitation tapers
off. Most snowfall will occur just on the highest peaks of the San
Bernardino and Riverside mountains, with only trace amounts down
at 7000 ft. Precipitation will taper off from north to south
through the day wednesday. Gusty southwest to west winds will also
accompany this system tonight into Wednesday afternoon. Gusts
45-55 mph are expected along the mountain ridges and upper desert
slopes, with gusts generally 25-40 mph for remaining mountain and
desert locations.
Mostly dry weather will prevail Wednesday night and Thursday. Some
lingering moisture and upslope flow may produce light
precipitation along the coastal slopes of the mountains. However,
with the high to our southwest expanding back westward and mostly
anti-cyclonic flow aloft, do not anticipate any precipitation for
the remaining areas. A weak wave tries to move through to the
north on Friday, but precipitation chances remain low with only
light amounts expected.
The storm for the New Year weekend has trended slower, with the
heaviest precipitation now expected late Saturday into Sunday
morning, tapering off through the day. While moisture with this
system isn't as deep or as ample as the first, much stronger
forcing and instability will occur as a deeper, more robust short
wave moves through. Snow levels will start at over 8,000 ft again,
but will lower to around 6,000 ft by Sunday morning, with
accumulating snow possibly impacting travel through the mountains
on New Years Day. Based on the current forecast, this will
actually be the wetter of the two systems. There will be another
break in the precipitation late Sunday and Monday. There is the
potential for yet another storm sometime the following Tuesday-
Wednesday, however, ensemble guidance is all over the place with
regards to timing and amounts. One thing that is for certain is
that we will remain in a cool and unsettled weather pattern
through much of next week.
&&
.AVIATION...
271645Z...Low clouds and lower VIS VCTY KSAN based around 300-500 FT
MSL will clear out by around 19z. Then BKN-OVC AOA 15,000 FT MSL
through tonight. Mid-level clouds with bases 3000-5000 FT MSL
increasing this afternoon. Chc SHRA/RA after 00z Wed for Orange/San
Bernardino/Riverside Counties and after 03z Wed for San Diego
County. Locally reduced vis of 2-4 SM in RA. SHRA/RA ending across
Orange County by 09z Wed,
Breezy W-SW winds developing after 18z Tue for northern mtns/High
Desert, expanding farther south through tonight. Winds look to peak
02z-14z Wed, with gusts of 30-45 kt, local gusts to 50 kt, highest
over/east of mtn peaks.
&&
.MARINE...
A series of storm systems will bring rain, gusty winds and elevated
seas this week, with the first occurring tonight into Wednesday.
Northwest wind gusts of 20 to 25 kt and combined seas of 7 to 10
feet will be possible in the outer coastal waters, with highest wind
and seas occurring south and west of San Clemente Island. Additional
chances for rain, elevated seas and strong winds will redevelop late
this week into the weekend.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory until 4 PM PST Thursday for Orange County
Coastal Areas-San Diego County Coastal Areas.
PZ...Small Craft Advisory from 4 AM to 10 PM PST Wednesday 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...Gregoria (Update)/SS (Previous Discussion)
AVIATION/MARINE...AdamsThe national radar mosaic for the moment the first event began.
2 high wind, 1 debris flow. Local standard time, as filed.
High winds occurred across the Riverside County Mountains mainly during the afternoon on December 27th. A peak wind gust of 77 mph occurred at the Toro Peak HPWREN site.
High winds occurred across the Apple and Lucerne Valleys on the afternoon of December 27th. A peak wind gust of 63 mph was observed at the Lucerne Valley SoCal-Edison site.
CalTrans report of rocks falling into both lanes of Highway 38 due to rainfall in the area. Storm total rainfall of 0.30-0.60 inch occurred across the region.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2022Every state in 2022This day in weather historyWarnings in California, December 2022
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: 1068262, 1068265, 1068240.