Heavy snow fell in the Cascades.
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.
Heavy snow fell in the Cascades.
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 17, 3:21 PM PST, 1 hour 39 minutes earlier.
Area Forecast Discussion
National Weather Service Seattle WA
321 PM PST Mon Dec 17 2018
.SYNOPSIS...A strong frontal system over the offshore waters will
move inland overnight and slow as it moves through the southern
interior of Western Washington Tuesday morning. The front will
finally exit to the southeast of the area midday Tuesday and
showery weather will continue into Wednesday. Another strong front
will move across the area on Thursday bringing more wind and rain.
A weak front may affect the area on Saturday, but a stronger front
will bring more wind and rain to the area late next weekend.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY/...The back edge of a strong
frontal system is moving through the offshore waters this afternoon.
It is expected to reach the Washington coastline around 10 PM
then slowly sag southeastward through the interior tonight through
Tuesday morning. This front will bring strong winds, heavy rains,
and heavy mountain snow to portions of the area as it passes.
Concerning wind: winds are gale force over the coastal waters and
are starting to increase along the coastline and in the north
interior. The latest short-term high-resolution models show winds
ramping up to 25 to 40 mph with gusts to 55 to 60 mph between
between 4 and 6 pm along the coast and continuing until the front
passes around 9 or 10 PM. In the north interior, winds will ramp
up about 7 PM and will continue until the front passes around
midnight. In both areas, winds are expected to be strongest near
shorelines and beaches. High wind warnings are in effect for these
areas.
Concerning rainfall: This incoming front has tapped into a
subtropical air mass west of Hawaii. The warm and moist air is
being transported rapidly ENE into our area under a strong jet
stream aloft. Thankfully, the front is progressive across most of
the area, and heavy rainfall rates over southwestern facing
mountain slopes and along the coast will only last 8-12 hours.
With the main jet stream axis aimed in at far southwestern
Washington and northwestern Oregon, the front will slow as it
drops southeast, and portions of the far southwest interior -areas
like the Willapa Hills in Lewis County and higher terrain east of
the I-5 corridor could see 2-5 inches of rainfall. A flood watch
has been issued for Lewis county in the south interior late
tonight through Tuesday afternoon.
Concerning snowfall: A period of heavy snow can be expected over
the mountains above 3500 to 4000 feet tonight through early
Tuesday. Snow levels will rise to above 5000 feet in the Olympics
late this evening limiting amounts at Hurricane Ridge to 5-10
inches. Stevens Pass and higher elevations surrounding Snoqualmie
Pass may see 12-18 inches of snow. Around 20 inches can be
expected a the higher and colder Mt Baker Ski Area. A winter storm
warning is in effect for the Cascades of Whatcom and Skagit
counties above 3500 feet, while winter weather advisories are in
effect for the Cascades of Snohomish and King counties above 3500
feet and the Olympics above 4000 feet.
Once the front moves southeast, expect strong onshore flow to
produce showery and breezy conditions later Tuesday through
Wednesday. The shower activity will increasingly become confined
to the mountains as we move toward Wednesday.
Another strong front will move through the area on Thursday. The
ECMWF is slower and not quite as deep as the GFS solution but
brings a deep low closer to Western Washington and a little later
in the day on Thursday. All-in-all, this front appears that it
will likely be a bit windier than tonight's front and rainfall
likely won't be quite as heavy. High wind watches or warnings may
be required for portions of the area as we get closer to the
event. Albrecht
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...Behind Thursday's
front conditions will become cooler with showers at times and snow
levels falling to 1500-2500 feet. Friday and Saturday may be dry
at times, but models show some weak shortwave trough activity
coming through a dirty ridge and across the region, especially on
Saturday. The next active frontal system moves through the area
Sunday with post-frontal showers on Monday. Forecasts represent a
model blend. Albrecht
&&
.AVIATION...A strong frontal system will move through the area
tonight with onshore flow behind the front on Tuesday. Southerly
flow aloft tonight will become westerly on Tuesday. The air mass
is moist and stable. It will become unstable on Tuesday.
Ceilings should lower tonight as a front arrives and rain
develops. MVFR low clouds should become widespread later tonight
with a few pockets of IFR.
KSEA...Mid and high clouds this evening should lower to MVFR after
midnight. There will also be some low level wind shear tonight
with strong south winds aloft. South wind 5-10 knots will
increase to 12-18 knots tonight and become gusty. Schneider
&&
.MARINE...A strong front will bring southerly gales to most waters
tonight. Moderate to strong onshore flow will follow on Tuesday.
There could be gale force west winds over the out Coastal Waters
around Tuesday evening. Onshore flow will ease on Wednesday.
A second strong frontal system will bring another round of
southerly gales to the area Wednesday night and Thursday. A third
round of southerly gales is likely on Saturday as the next in a
parade of strong storms moves into the area.
20-22 foot west swell are expected to affect the coast on
Wednesday. There is a chance even larger waves could affect the
coast Thursday. The combination of high astronomical tides, tidal
anomalies due to unusually low surface pressure, and large waves
could result in coastal flooding on Thursday. There is still a
good deal of uncertainty with the details but this will need to be
watched. Schneider
&&
.HYDROLOGY...Flooding continues on the Skokomish river in Mason
county. The river slowly receded today but remained within minor
flood stage. The river will rise again tonight as our next wet
frontal system moves in.
A Flood Watch is in effect for Lewis county from late tonight
through Tuesday afternoon. Heavy rainfall in SW Washington will
force sharp rises in the rivers, especially the rivers flowing off
the Willapa Hills where 4-5 inch rainfall bullseyes are forecast.
The Chehalis river near Doty is forecast to crest just below
minor flood stage. However, minor flooding is possible if rainfall
rates in the basin exceed guidance.
Looking ahead, we'll see another round of heavy precipitation on
Thursday but so far it looks like this will mainly affect the
Skokomish. Otherwise, additional river flooding is not
anticipated. 33
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch from late tonight through Tuesday afternoon for
Cascades of Pierce and Lewis Counties-Southwest Interior.
Winter Weather Advisory from 6 PM this evening to 6 PM PST
Tuesday for Cascades of Snohomish and King Counties.
Winter Storm Warning from 6 PM this evening to 6 PM PST Tuesday
for Cascades of Whatcom and Skagit Counties.
High Wind Warning until 1 AM PST Tuesday for Admiralty Inlet
Area-San Juan County-Western Skagit County-Western Whatcom
County.
High Wind Warning until 10 PM PST this evening for Central Coast-
North Coast.
Winter Weather Advisory until 4 AM PST Tuesday for Olympics.
PZ...Small Craft Advisory for rough bar until 4 PM PST Tuesday for
Grays Harbor Bar.
Gale Warning until 10 PM PST this evening 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.
Gale Warning until 4 AM PST Tuesday for Admiralty Inlet-Central
U.S. Waters Strait Of Juan De Fuca-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 Wednesday for Puget Sound
and Hood Canal.
&&
www.weather.gov/seattle2 heavy snow. Local standard time, as filed.
Paradise on Mount Rainier received 19 inches of snow in 24 hours, and 25 inches overall.
Snoqualmie Pass received 12 inches of snow in 12 hours. Stevens Pass received 18 inches of snow in 24 hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2018Every state in 2018This day in weather historyWarnings in Washington, December 2018
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: 791208, 791207.