Northeast low level flow associated with a Fraser outflow event produced heavy lowland snow along the Eastern Strait of Juan de Fuca.
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.
Northeast low level flow associated with a Fraser outflow event produced heavy lowland snow along the Eastern Strait of Juan de Fuca.
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 31, 8:20 PM PST, 4 hours 40 minutes earlier.
Area Forecast Discussion
National Weather Service Seattle WA
820 PM PST Sat Dec 31 2016
.SYNOPSIS...Showers in the lowlands of Western Washington will turn
to snow overnight and taper off over Western Washington Sunday
morning. Cold Canadian air will move south over the region Sunday and
Monday. After several days of cold dry weather, there will be an
increasing chance of precipitation late next week as temperatures
moderate.
&&
.SHORT TERM...The snow that fell earlier today was mostly a fake-out
that occurred before strong onshore flow developed this evening. In
fact pressures have been falling rapidly all afternoon and evening
as the surface low develops over the region and the OTH-SEA gradient
was at +10mb at 8pm. In any season this is a strong marine push, and
marine air certainly does not help it snow in Seattle. That said,
Whatcom county is getting some wet snow showers this evening and many
of the webcams up there do show a little snow--elsewhere, you would
probably have to be on a pretty decent hill or in the foothills of
the Cascades to see much. Happily for snow lovers, it will get
rather cold aloft overnight as a cold upper low moves south
through the region--it will be -36c by daybreak and 500mb and with
that sort of temp aloft, any showers can quickly give a location a
couple inches of snow. There is not much precip in the models this
evening, so I am not hopeful--but I am also not brave enough to
take down the winter weather advisories when the best chance of snow
showers is still 6-12 hours away as I type this--3am to 9am.
Anyway, for now strong onshore flow this evening is keeping temps in
the lowlands above freezing but as the cold air aloft shifts south
and the onshore flow starts to relax the showers will turn to snow
overnight--but only as they taper off anyway. There are winter
weather advisories up for a few areas for 1-3" of snow--that might
very well happen in a few areas later tonight as the cold air aloft
moves overhead. There will be the tricky part when it is cold enough
but perhaps not yet too dry--as I said, 3am to 10am might be the best
window for scattered snow showers for the Seattle metro area. What is
an easy forecast is that wintry Canadian air will arrive through
Monday
with Fraser outflow and a hard freeze for all of Western Washington.
Monday and Tuesday nights should both be rather cold with teens in
the outlying areas and 20s elsewhere, highs will struggle and fail
to get above freezing in some areas.
.LONG TERM...Temperatures will remain below normal but slowly
moderate through the end of the week and there is a good chance that
precipitation will return by next weekend and that snow levels will
be low--perhaps still near sea level.
&&
.AVIATION...An upper trough will move over the area this evening.
Westerly flow aloft will ease and become variable tonight as a
weak upper low moves overhead Sunday morning. At the surface, a
front and an associated low will move south through the area
tonight. Fraser outflow will develop Sunday. The air mass is
moist and stable.
Areas of low clouds have become fairly widespread this evening,
with areas of light rain, snow, or rain and snow mixed. Low clouds
should continue to increase overnight as the front moves through.
Ceilings will improve from north to south Sunday as drier air
moves in behind the front. Precipitation should become
predominantly snow from north to south tonight as colder air
moves into the region.
KSEA...South wind 8-12 kt gusting 20 kt, switching to north
approximately 2 am and rising to 10-18 kt gusting 26 kt Sunday.
The wind will switch to northerly at KBFI about an hour earlier
than at KSEA. Low clouds tonight. Rain showers should change to
snow showers a little after midnight tonight with about inch of
accumulation possible by Sunday morning. Snow showers will taper
late Sunday morning and ceilings should improve in the afternoon.
McDonnal
&&
.MARINE...A surface low and an associated cold front will move
south through the waters tonight. Strong west to northwest flow
will develop behind the front over the Coastal Waters and Strait
of Juan De Fuca. The wind in the central and eastern Strait of
Juan de Fuca has risen to gale force, so a gale warning will be
issued. High-end small craft advisory winds will continue over the
coastal waters. 3Strong northeast offshore flow will develop
Sunday as high pressure builds into southern British Columbia.
Gale northeast winds are likely for the Northern Inland waters and
much of the Strait of Juan De Fuca.
Northeast offshore flow will continue Monday through Thursday.
Gale force northeast winds will probably come down to small craft
advisory strength for the Northern Inland waters Monday night.
Schneider
&&
.HYDROLOGY...River flooding is not expected the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 10 AM PST Sunday for Bellevue and
Vicinity-Bremerton and Vicinity-East Puget Sound Lowlands-
Hood Canal Area-Seattle and Vicinity-Tacoma Area.
Winter Weather Advisory until 4 AM PST Sunday for Western Skagit
County-Western Whatcom County.
Wind Advisory from 6 AM to 6 PM PST Sunday for San Juan County-
Western Skagit County-Western Whatcom County.
PZ...Small Craft Advisory for rough bar until noon PST Sunday for
Grays Harbor Bar.
Small Craft Advisory until 6 AM PST Monday 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 midnight PST tonight for Central U.S. Waters
Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
Juan De Fuca.
Gale Warning from 6 AM Sunday to 4 AM PST Monday for 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 midnight PST tonight for Admiralty
Inlet-Northern Inland Waters Including The San Juan Islands.
Small Craft Advisory from 6 AM Sunday to midnight PST Sunday
night for Admiralty Inlet-Puget Sound and Hood Canal.
&&
www.weather.gov/seattle
You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.htmlPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1027 PM PST SAT DEC 31 2016
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1026 PM SNOW 4 NNE LA CONNER 48.45N 122.47W
12/31/2016 M2.2 INCH SKAGIT WA TRAINED SPOTTER
1 HOUR SNOWFALL
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1236 AM PST SUN JAN 01 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1236 AM SNOW 4 NNE LA CONNER 48.45N 122.47W
01/01/2017 M3.5 INCH SKAGIT WA TRAINED SPOTTER
&&1 heavy snow. Local standard time, as filed.
Five CoCoRaHS stations reported heavy snow between midnight and noon of January 1, with amounts ranging from 3.5 to 7.0 inches.
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, January 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: 677524.