A very cold airmass pushed into Western Washington at the end of December, resulting in cold air amidst sufficient moisture and lift as a modified arctic frontal boundary slid south. This made for significant lowland and mountain snow, with a period of drier but much colder weather for the following days.
Every event with a place to put it; 1 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 SEW wrote it up.
A very cold airmass pushed into Western Washington at the end of December, resulting in cold air amidst sufficient moisture and lift as a modified arctic frontal boundary slid south. This made for significant lowland and mountain snow, with a period of drier but much colder weather for the following days. Several climate sites reached record low temperatures during and shortly after the winter 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 Seattle, WA wrote its last area forecast discussion before the first event at Dec 25, 9:33 AM PST, 2 hours 27 minutes earlier.
Area Forecast Discussion
National Weather Service Seattle WA
933 AM PST Sat Dec 25 2021
.UPDATE...Snow and rain across much of the area this morning, the
the best chance for accumulating snow being recorded across areas
of Whatcom/Skagit County with a heavy band over portions of these
areas. Activity is more scattered along the coast and across
southern areas, with light wet snow accumulations with the
heaviest shower activity into this evening. Winds will be strong
across Whatcom County. Winter Weather Advisory for much of the
lowlands with Winter Storm Warning for areas of northern
Olympics and Whatcom/Island/Skagit.
&&
.SYNOPSIS...Areas of lowland snow through Sunday with colder
temperatures. Dry and cold weather for Monday. Cold Tuesday and
Wednesday with a weather system moving along the coast Tuesday.
Temperatures will increase a bit Thursday with another weather
system potentially bringing snow to Western Washington.
&&
.SHORT TERM /TODAY THROUGH MONDAY/...An upper trough just off the
coast will keep the weather showery today. It will be marginally
cold enough for snow or a rain/snow mix for most of the area
today. Winds will be southerly and temperatures slightly above
freezing. This should mostly limit lowland snow accumulations
today with the best chances for an inch or so over the higher
hills or in locally heavier shower bands that might set up.
The exception to this will be the Strait of Juan de Fuca and
Western Whatcom/Western Skagit Counties. Fraser outflow has
already begin over Western Whatcom County with colder air seeping
in. These northeast winds will also lead to upslope in the Strait
on the north side of the Olympics. Snow accumulations of 2-5
inches are possible in these areas today.
Tonight and Sunday look like the best chance for widespread snow
accumulations across Western Washington. A surface low will move
onshore over SW WA Sunday morning with winds turning northerly
all areas and modified arctic air moving into the area. It will
remain showery with the upper trough moving over the area.
Ensemble solutions suggest the mostly likely scenario is 1-3
inches for most areas with higher amounts possible in locally
heavier bands. As always, there is much uncertainty with exact
amounts but overall this does not seem like a big snowstorm for
most of the area. The Cascades will also be getting a good shot of
snow through Sunday with difficult driving conditions expected in
the passes.
Northerly flow aloft will quickly dry things out Sunday night
with the story then becoming cold weather. Highs today will be
mostly in the 30s, then mid 20s to lower 30s on Sunday. By Monday,
highs will be in the 20s all areas. Parts of Western Whatcom
County might have highs in the upper teens on Monday. Lows Monday
morning will be in the teens most areas with single digits for
Western Whatcom County.
In addition, increasing Fraser outflow will bring windy
conditions to Western Whatcom County, Wester Skagit County, and
the San Juan Islands the next few days. Gusts to 50 mph are
possible in these areas. Wind chills could drop to -5 to -10 over
Western Whatcom County on Sunday and perhaps as low as -15 Sunday
night/Monday morning.
There is also a small chance of thunderstorms near the coast
today and Sunday with the upper trough.
Finally, high astronomical tides and anomalously low atmospheric
pressure could lead to minor tidal overflow over Puget Sound
around the time of high tide today and again on Sunday. 16
.LONG TERM /TUESDAY THROUGH FRIDAY/...An upper short wave in the
north/northwest flow aloft will mostly pass to the west Monday
night and Tuesday but the coast and Southwest Interior could perhaps
get an inch of new snow from this glancing blow. Temperatures will
moderate a little but it will remain cold with highs in the mid
20s to lower 30s and lows mostly 15-25.
Wednesday should be another cold and dry day with northerly flow
aloft. There is enough spread in the ensembles to keep a mention
of a slight chance of snow in the forecast however. Temperatures
will be about the same as Tuesday.
A wetter and slightly warmer system will move into the area from
the northwest Wednesday night and Thursday. Highs are expected to
warm into the mid 30s to lower 40s with southerly winds developing
for most of the area. It's too far out to pin down rain/snow
details but a likely scenario is precipitation starting as snow
Wednesday night then gradually changing to rain on Thursday with
snow lingering longest in the usual interior cold pockets. Drier
northerly flow is expected on Friday in the wake of Thursday's
weather system. It will remain chilly with highs in the mid 30s
to lower 40s. 16
&&
.AVIATION...South to southwesterly flow aloft for much of the day
today as an upper level low digs in off the coast. The atmosphere
remains moist and generally stable.
Mix of cigs over W WA this morning as scattered showers remain in
place over much of the area. Most locations ranging MVFR to IFR,
however along the coast, starting to see some VFR conditions emerge.
Radar trend seems to support that given a temporary break in the
echoes, however given that the upper low is still in place and
echoes are still present over the coastal waters, safe to say that
lower cigs remain a possibility for those coastal terminals as these
showers make their way inland. Minimal improvement to cigs expected
over the TAF period, although as the low slowly moves east, some
lifting is possible Sunday afternoon.
Southerly winds to persist at 8-12 kts, becoming gusty to 20 kts at
times for areas across the southern Sound. Switch to northerly winds
expected between 06-09Z SUN. Worth pointing out that as southerly
surface winds transition to more northerly, the penetration of
colder air will allow for any precip associated with showers to
become either a wintery mix or snow, expected to be all snow by 12Z
Sunday morning. The exception to this will be BLI, where northerly
winds are already in place and, as such, showers there continue to
fall as snow.
KSEA...MVFR ceilings for the TAF period. Rain will continue at the
terminal through the day as winds are expected to remain southerly
at 7-12 kts. Winds may ease somewhat during the day before becoming
northerly later tonight (06-09Z). Temperatures at that time will be
cold enough that showers moving over the area will be in the form of
snow, with accumulations possible. 14/18
&&
.MARINE...A low pressure system will slowly fill over the area
today as a modified arctic front drops south through the region.
A small craft advisory remains in effect for the coastal waters
for high end small craft winds and seas above 10 feet. Winds
across the Northern Inland waters will increase late today as the
Fraser River outflow strengthens across the area. North/northeasterly
winds will persist throughout the weekend, likely maintaining
headlines across the majority of the area waters through early
next week. Precipitation will likely change over to snow across
the area waters today. With winds and temperatures well below
freezing tonight into early next week (especially over the
Northern Interior waters) freezing spray will become a concern and
will need to be monitored going forward. All that said, inherited
headlines and forecast look good and see no reason for an update for
the late morning forecast package. 14/18
&&
.HYDROLOGY...River flooding is unlikely for the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 4 PM PST Sunday for Bellevue and
Vicinity-Bremerton and Vicinity-Central Coast-East Puget
Sound Lowlands-Everett and Vicinity-Hood Canal Area-Lower
Chehalis Valley Area-North Coast-San Juan County-Seattle
and Vicinity-Southwest Interior-Tacoma Area.
Coastal Flood Advisory until 1 PM PST this afternoon for
Admiralty Inlet Area-Bremerton and Vicinity-Everett and
Vicinity-Hood Canal Area-Seattle and Vicinity-Tacoma Area.
Winter Weather Advisory until 4 AM PST Sunday for Cascades of
Pierce and Lewis Counties-Cascades of Snohomish and King
Counties-Cascades of Whatcom and Skagit Counties.
Wind Advisory until 4 AM PST Monday for Western Whatcom County.
Winter Storm Warning until 4 PM PST Sunday for Admiralty Inlet
Area-Eastern Strait of Juan de Fuca-Western Skagit County-
Western Strait of Juan De Fuca-Western Whatcom County.
Wind Advisory from 4 PM this afternoon to 4 AM PST Monday for
San Juan County-Western Skagit County.
PZ...Small Craft Advisory until 4 PM PST this afternoon for Grays
Harbor Bar-Puget Sound and Hood Canal.
Small Craft Advisory until 4 AM PST Sunday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From Cape Flattery To James Island Out 10 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville Out 10
Nm-Coastal Waters From Point Grenville To Cape Shoalwater
10 To 60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm-West Entrance U.S. Waters Strait Of
Juan De Fuca.
Small Craft Advisory until 4 PM PST Sunday for East Entrance
U.S. Waters Strait Of Juan De Fuca.
Gale Warning until 10 PM PST Sunday for Northern Inland Waters
Including The San Juan Islands.
Small Craft Advisory from 4 PM this afternoon to 4 PM PST Sunday
for Central U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 4 AM to 10 PM PST Sunday for Admiralty
Inlet-Puget Sound and Hood Canal.
&&
www.weather.gov/seattleThe national radar mosaic for the moment the first event began.
15 heavy snow, 7 cold/wind chill, 1 high wind. Local standard time, as filed.
A winter storm brought heavy snow to Western Whatcom County around the Christmas holiday. Reports generally ranged from 8 to 15 inches.
Heavy snow affected much of Western Skagit County during the final week of December. New snow accumulations generally ranged from 6 to 12 inches.
A Winter Storm affected most of the San Juan Islands during the final week of December. Reports from the Islands generally ranged from 3 to 6 inches.
A Winter Storm brought heavy snow to the northern side of the Olympic Peninsula during the last week of December. Snow was orographically enhanced, resulting in an average of 10-20 inches for locations along the East Strait of Juan de Fuca, with most of the 20 inch reports located just south of Port Angeles.
Amidst strong Fraser Outflow, the ASOS at the Bellingham. Airport measured a wind gust of 63 mph around 0730 local time.
With Western Whatcom experiencing the strongest Fraser Outflow at the beginning of the winter storm event, a record low temperature was set at Bellingham of 11F, which replaces the old record of 12F set in 1971.
A Winter Storm affected the Everett area right after the Christmas holiday as modified arctic air pushed into the area. Average snow totals ranged from 5 to 7 inches.
A Winter Storm affected the North Coast of Washington during the final week of December. Average snowfall totals were around 4 inches.
A Winter Storm affected the Central WA Coast just after the Christmas holiday. Average snowfall totals ranged generally from 3 to 6 inches, although isolated higher amounts around 9 inches were noted.
A Winter Storm brought an average of 6 to 12 inches of new snow to the Hood Canal area during the final week of December.
A Winter Storm brought heavy snow to the Southwest Interior during the last week of December as a modified arctic airmass moved in. An average of 5 to 10 inches was reported after the storm across the area.
A Winter Storm during the final week of December resulted in an average of 4 to 6 inches across the Tacoma area.
A late December Winter Storm brought an average of 3 to 5 inches to the Bremerton area as a modified arctic front pushed across the area.
A Winter Storm brought heavy snow to the Seattle area during the last week of December as a modified arctic frontal boundary pushed across the area. The Seattle metro area received an average of 4 to 6 inches of snowfall.
A Winter Storm during the last week of December resulted in an average snowfall total of 4 to 6 inches across the Bremerton area.
A winter storm brought heavy snow to the Lower Chehalis Valley Area, resulting in generally 8-12 inches of new snow accumulation.
A Winter Storm brought heavy snow to the Admiralty Inlet Area, including Whidbey Island and Camano Island. Snowfall totals in this area generally ranged from 3-8 inches, with isolated higher amounts towards 10 inches, especially the northern portion of Whidbey Island.
A record low was reported at the Quillayute ASOS on the morning of Dec 27th at 19F. This replaces the previous record low temperature of 23 from 1978.
A record low was reported at the Bellingham ASOS on the morning of Dec 27th at 9F. This replaces the previous record low temperature of 12 from 1971.
A record low was reported at the Hoquiam ASOS on the morning of Dec 27th at 25F. This replaces the previous record low temperature of 26 from 1954.
A record low was reported at the SeaTac ASOS on the morning of Dec 27th at 20F. This replaces the previous record low temperature of 22 from 1948.
A record low was reported at the SeaTac ASOS on the morning of Dec 28th at 17F. This replaces the previous record low temperature of 20F from 1968.
A record low was reported at the Hoquiam ASOS on the morning of Dec 28th at 21F. This replaces the previous record low temperature of 25F from 1978.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2021Every state in 2021This day in weather historyWarnings in Washington, 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: 998736, 998738, 998739, 998740, 998623, 998624, 998741, 998742, 998743, 998744, 998745, 998746, 998747, 998748, 998749, 998810, 998812, 998625, 998626, 998627, 998628, 998629, 998630.