An end of the year Pacific storm system brought breezy to locally windy condition to portions of the Western Washington lowlands on December 30.
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.
An end of the year Pacific storm system brought breezy to locally windy condition to portions of the Western Washington lowlands on December 30.
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 30, 4:23 AM PST, 3 hours 37 minutes earlier.
Area Forecast Discussion
National Weather Service Seattle WA
423 AM PST Wed Dec 30 2020
.SYNOPSIS...A series of systems will bring lowland rain, impactful
mountain snow, and gusty winds to Western Washington today and
again over the weekend. Wet and unsettled weather looks to
persist into the first week of 2021.
&&
.SHORT TERM /TODAY THROUGH FRIDAY/...The first in a series of
weather systems will continue to make its way across the region
today, bringing lowland rain, heavy mountain snow, and breezy
winds to portions of Western Washington. Latest observations this
morning indicate that locations along the Pacific Coast have
already received about an inch of rain, while locations near the
Sound generally range from a couple hundredths to a quarter of an
inch as of 2 AM this morning. Areas near the foothills have
generally received near half an inch so far. Latest NWAC observations
show about 5 inches of fresh snow at Stevens Pass and 7 inches
for Snoqualmie Pass over the past couple of hours. Overall, expect
lowland rain and mountain snow to continue into Thursday morning.
Gusty winds this morning will gradually ease this afternoon.
Here's what to expect:
Mountain Snow: Periods of heavy snow are expected across portions
of the Cascades and Olympics today. Snow levels will gradually rise
across the region throughout the morning, however, expect this to
be short lived as snow levels are expected to fall again this
afternoon and evening. Snow levels look to briefly rise near pass
level at Snoqualmie this morning, so could see snow transition to
a rain- snow mix for a few hours. Do not expect this to hinder
snow totals much for the area however. The passes could see an
additional 10 to 18 inches of snow through Thursday morning, with
up to 2 feet of fresh snow for elevations above 4500 feet. Those
with travel plans across the passes should remain aware of current
road conditions and be prepared for winter weather driving.
Rain: Periods of moderate to heavy rainfall will continue today,
especially if showers become more convective later this morning
and afternoon. Can expect to see an additional 1-3 inches for
areas along the Pacific Coast through Thursday morning, with an
additional half an inch to 1 inch for areas along the Sound.
Additional rainfall amounts for areas along the Cascade foothills
of 1 to 1.5 inches will be possible. With thunderstorms still a
possibility for the locations along the Pacific coast, could see
locally higher amounts for areas in the vicinity of any brief
heavy downpours.
Winds: Southeasterly winds have picked up across the region
overnight and will peak this morning before gradually easing later
this afternoon and evening. Strongest winds still on tap to be
near the Pacific Coast, Admiralty Inlet, the San Juans, and areas
near the northern inland waters. Winds 25 to 40 mph will be
possible, with gusts to 50 mph.
Thunderstorms: Guidance still supports a slight chance of
thunderstorms along the coast late this morning and into the
afternoon. With upper level temps decreasing to near -25 C late
and a shortwave trough moving across the area, cannot completely
rule out a lightning strike or two in the vicinity of the frontal
system.
Showers will linger into Thursday morning, before a shortwave
ridge traverses the region, giving Western Washington a brief
break ahead of the next system arriving on Friday. Another round
of lowland rain and mountain snow is on tap for Friday, before
another impactful system moves across the region Saturday and
Sunday.
.LONG TERM /SATURDAY THROUGH TUESDAY/...Wet and unsettled weather
will continue over the weekend as another impactful system moves
across Western Washington. Expect another round of heavy lowland
rain, heavy mountain snow, and potentially more widespread stronger
winds Saturday and Sunday. In addition will need to monitor the
potential for coastal flooding for coastal areas over the
weekend- with the combination of high astronomical tides and the
potential for strong winds with the incoming system. Details for
this weekend's system will be refined in the coming days, so stay
tuned to see how the forecast evolves. Ensembles continue to show
upper level troughing influencing the region into early next week,
so expect wet and active weather to continue into the first week
of January. 14
&&
.AVIATION...A vigorous frontal system is approaching Western
Washington this morning with strong southwest flow aloft. The air
mass is very moist with widespread MVFR ceilings and areas of IFR.
These conditions are expected to persist across the region through
the day. Gusty SE surface winds are expected near the coast and
across the interior north of KPAE through midday. The front will
move onshore late this morning then stall across the region into
tonight for a continuation of low MVFR/IFR ceilings in rain and
surface visibilities down to 3-5SM at times.
KSEA...Ceilings expected to alternate between low MVFR and IFR in
rain throughout the day and into tonight as front moves into the
area and stalls. Southerly surface winds will gradually ramp up
later this morning and should be 10 to 15 knots from 18Z through
this evening with gusts of 20 knots possible. Winds just above
surface will rise to near 40 knots at 2000 feet before daybreak
today and have included mention of LLWS potential in TAF through
late this morning. 27
&&
.MARINE...Expecting an extended period of active weather to
impact area waters through early next week as a series of
strong frontal systems move through the region. A frontal system
moving onshore later this morning will bring gales to the coastal
waters as well as Northern Inland and adjacent waters. Coastal
seas will be in the double digits from today through the
foreseeable future for an extended period of rough seas.
The next in a series of systems arrives Thursday night into Friday
with another round of likely gales for the coastal waters and
portions of the inland waters. Forecast models are inconsistent with
the details for the weekend and early next week, but confidence
remains high that this will be a very active period with additional
periods of gale force wind (or higher) affecting a large swath of
area waters. In addition, coastal seas are expected to rise above 20
feet over the weekend. 27
&&
.HYDROLOGY...The first in a series of weather systems will continue
to move through the region today. Snow levels will briefly rise
this morning, before falling again late this afternoon and evening.
Overall, expect lower snow levels to prevent runoff and river
flooding for most Western Washington rivers into the weekend. The
exception remains the Skokomish River, which is forecast to reach
minor flood stage late this morning. A flood watch is currently
in effect for Mason County. Expect the river to recede slightly
before rising again over the weekend as another pair of systems
move across Western Washington. 14
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 4 AM PST Thursday for Cascades of
Pierce and Lewis Counties-Cascades of Snohomish and King
Counties-Cascades of Whatcom and Skagit Counties.
Flood Watch from 7 AM PST this morning through Thursday
afternoon for Hood Canal Area-Lower Chehalis Valley Area-
Olympics.
Wind Advisory until 1 PM PST this afternoon for Admiralty Inlet
Area-San Juan County-Western Skagit County-Western Whatcom
County.
Wind Advisory until 10 AM PST this morning for Central Coast-
North Coast.
Winter Weather Advisory until 10 PM PST this evening for
Olympics.
PZ...Small Craft Advisory until 4 PM PST Thursday for Grays Harbor
Bar.
Gale Warning until 4 PM PST this afternoon 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.
Gale Warning until 6 PM PST this evening for Admiralty Inlet-
East Entrance U.S. Waters Strait Of Juan De Fuca-Northern
Inland Waters Including The San Juan Islands.
Small Craft Advisory until 4 AM PST Thursday for Central U.S.
Waters Strait Of Juan De Fuca-Puget Sound and Hood Canal-
West Entrance U.S. Waters Strait Of Juan De Fuca.
&&
www.weather.gov/seattle1 strong wind. Local standard time, as filed.
Fort Ebey State Park was forced to close for a period of time on December 30 due to numerous downed trees, per WA State Parks. The ferry service from 8am-1030am from Port Townsend and Coupeville were cancelled due to high wind and rough seas.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2020Every state in 2020This day in weather historyWarnings in Washington, December 2020
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: 934887.