Heavy snow fell in the Olympics and north 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 Olympics and north 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 19, 4:30 AM PST, 1 hour 30 minutes earlier.
Area Forecast Discussion
National Weather Service Seattle WA
430 AM PST Tue Dec 19 2017
.SYNOPSIS...A strengthening low center will track from near
Forks to Mount Vernon this morning. A strong cold front will
sweep in behind the low center, ushering in a colder air mass and
lowering snow levels later today. Look for heavy snow in the
mountains today and gusty winds with the frontal passage. Showers
will follow the front tonight and then end on Wednesday. A cold
and dry air mass will be in place starting Wednesday and
continuing through Christmas Day. On Thursday night and Friday
morning, a system diving southeast through B.C. will increase
clouds with a low chance of some light lowland snow.
&&
.SHORT TERM...Nice baroclinic leaf signature in satellite imagery
just off the coast early this morning. This is classic of
cyclogenesis and the early stages of a rapidly deepening low
center. Models are in lock-step agreement with bringing the low
center onshore later this morning near Destruction Island and
continuing E-NE from there. To the right of the low track, south
winds will pick up in the next few hours, thus the Wind Advisory.
Looking for peak wind gusts around 45 mph south of the low track.
Perhaps the more interesting thing is what is happening to the
left of the low track. Heavy precip, strong dynamical cooling
aloft, and a northeast upslope breeze into Port Angeles really
cooled the column overnight. CLM is now reporting 33F and snow.
The UW-WRF seems to be the only model right now explicitly showing
snow along the Strait this morning. It is, in fact, quite bullish,
showing 7 inches or so of snow at Port Angeles this morning. In
the official forecast, have indicated snow level around 100 to 200
feet with lesser snow accumulation above that. Have gone with a
Winter Weather Advisory from Port Angeles west to near Clallam Bay
for up to 4 inches of snow. Counting of some melting as the snow
falls to avoid the heavier snowfall accumulation solution.
In the mountains, Snoqualmie Pass is still reporting snow. The
temporary changeover to rain later this morning is appearing
briefer, so have lowered the snow level forecast today to 3000
feet and increased the forecast accumulation at Snoqualmie Pass.
Once the low exits east this afternoon, a strong and sharply
defined cold front will quickly sweep across Western Washington.
Snow levels will drop to 1500 feet around sunset, and widespread
precip will turn to showers. Showers will focus in the Cascades
and along a southward-moving wind shift at the leading edge of
northerly winds emanating at first from the Strait of Georgia,
then from the Fraser River Valley in B.C.. With a colder and drier
air mass spreading in from interior B.C., showers will taper off
and eventually end on Wednesday. Over the interior lowlands, this
will be a case where sufficiently cold air for snow is basically
chasing the last few showers out. As such, could be a few
snowflake sightings and some spotty light dustings of snow on
Wednesday morning, but this should largely be a non-impactful
occurrence.
Thursday will simply be cold and dry under northwest flow aloft.
Haner
.LONG TERM...Still eyeing a chance of light lowland snow on
Thursday night and Friday morning. This is still far from certain,
though. All models show an upper impulse and surface cold front
sweeping southeast through the interior of B.C. early Friday. The
ECMWF and Canadian models are consistent with their previous runs
in producing precip over Western Washington. Meanwhile, the GFS is
also consistent with its previous runs in keeping the period dry
and precip-free. The NAM is siding with the GFS. Only about 3 of
the GFS's 20 ensemble members show measurable precip at Seattle
early Friday. So the model stalemate continues. The end result is
30-40 PoPs for light snow and rain along the I-5 corridor. If the
most bullish models are right, could get up to 2 inches of snow
in places. This is far from certain at this point, so check back.
Friday night through Sunday night look dry and cool, as an upper
ridge axis approaches and passes. Latest GFS and ECMWF now show a
north-south oriented front spreading precip onto the coast later
Christmas Day, but GFS ensembles are not very supportive.
Official forecast remains dry for now, but day shift will need to
re-evaluate. Haner
&&
.AVIATION...A frontal system will move through the area today. An
upper low will cross the area tonight. Southwest flow aloft will
become variable tonight. The air mass is moist and stable.
There will be a mix of MVFR and IFR low clouds across the area
today. There will be some drying behind the front later today and
tonight but some low clouds will linger. A Puget Sound Convergence
Zone is expected to sag south through Puget Sound tonight.
KSEA...MVFR ceilings should lower to IFR this morning as heavier
rain arrives. Ceilings should lift a bit late in the day as a
front pushes inland. A Puget Sound Convergence Zone could bring
lower clouds again for a few hours tonight. Light northeast wind
will become south 10 to 20 knots with gusts 30-35 knots today.
Winds will ease late in the day and shift to north after midnight
tonight. Schneider
&&
.MARINE...A vigorous frontal system will move through the area
today. An associated surface low will move onto the coast a
little south of UIL this morning and then move inland on an
east/northeast track. Gale force winds are likely south of the
low track with small craft advisory strength winds elsewhere.
There could also be a brief westerly gale in the Strait of Juan de
Fuca this afternoon behind the low.
Offshore flow will develop Wednesday and continue Thursday
through Saturday. A 1050 MB surface high moving into southeast
British Columbia will strengthen the offshore flow Friday and
Friday night. Schneider
&&
.HYDROLOGY...River flooding is not expected the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory until 4 PM PST this afternoon for Bellevue and
Vicinity-Bremerton and Vicinity-East Puget Sound Lowlands-
Hood Canal Area-Lower Chehalis Valley Area-Seattle and
Vicinity-Southwest Interior-Tacoma Area.
Winter Storm Warning until 10 PM PST this evening for Cascades
of Pierce and Lewis Counties-Cascades of Snohomish and King
Counties-Cascades of Whatcom and Skagit Counties.
Winter Weather Advisory until 11 AM PST this morning for Eastern
Strait of Juan de Fuca-Western Strait of Juan De Fuca.
Winter Storm Warning until 3 PM PST this afternoon for Olympics.
Wind Advisory until 10 AM PST this morning for Central Coast.
PZ...Gale Warning until 10 AM PST this morning for 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.
Small Craft Advisory until 10 AM PST Wednesday for Coastal
Waters From Cape Flattery To James Island 10 To 60 Nm.
Gale Warning from noon today to 6 PM PST this evening for
Central U.S. Waters Strait Of Juan De Fuca-East Entrance
U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory until 4 PM PST this afternoon for Admiralty
Inlet-Northern Inland Waters Including The San Juan Islands.
Small Craft Advisory until 4 PM PST this afternoon for West
Entrance U.S. Waters Strait Of Juan De Fuca.
Gale Warning until 4 PM PST this afternoon for Puget Sound and
Hood Canal.
Small Craft Advisory until 10 PM PST this evening for Coastal
Waters From Cape Flattery To James Island Out 10 Nm.
&&
www.weather.gov/seattle2 heavy snow. Local standard time, as filed.
Mt. Baker picked up 19 inches in 24 hours, 6 AM 12/19 to 6 AM 12/20.
The Waterhole SNOTEL near Hurricane Ridge got 19 inches of snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2017Every state in 2017This day in weather historyWarnings in Washington, December 2017
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: 799290, 799291.