A landslide occurred near the town of Oso.
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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 landslide occurred near the town of Oso.
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 Apr 2, 7:30 PM PST, 4 hours 30 minutes earlier.
Area Forecast Discussion
National Weather Service Seattle WA
830 PM PDT Sun Apr 2 2017
.SYNOPSIS...Dry weather will return Monday and Tuesday as an upper
level ridge moves over the region. The weather will become wetter
again late this week as a series of fronts arrive.
&&
.SHORT TERM...Scattered showers this evening will end later tonight
as an upper trough over the area shifts inland. Monday will be dry
with an upper ridge moving to the coast and cool dry northerly flow
aloft over Washington. The freezing level is around 3000 feet. Low
temperatures tonight will dip into the 30s in most places. A few
upper 20s are not out of the question if the wind dies and some
clearing happens--note the KOLM GFS MOS calls for 29 tonight.
On Monday, morning cloudiness should give way to some afternoon
sunshine. Highs will rise a few degrees but still be in the 50s,
which is slightly below normal.
The upper ridge will slowly cross the area on Tuesday for another
generally dry day. A warm front from an approaching frontal system
will bring increasing clouds however and introduce a chance of rain
over western areas, mainly in the afternoon. Highs in the interior
will warm a few more degrees in the warm sector. A few spots might
reach 60.
A trailing cold front will move to the coast Tuesday night and
Wednesday but it will be very slow to push inland with the southwest
flow aloft nearly parallel to the front. The coast should see some
rain during this period most much of the interior could remain dry.
There are differences in the models with the ECMWF being a bit more
progressive and bringing rain to the interior Wednesday. The forecast
is a blend of the models for now. Schneider/Burke
.LONG TERM...Previous discussion...An upper trough will be offshore
Thursday through Sunday. Several short waves rotating around the
upper trough will push into Western Washington during this period
resulting in showery weather with slightly below normal
temperatures. Schneider
&&
.AVIATION...An upper trough will shift east tonight with high
pressure aloft building over the Pacific Northwest Monday and Monday
night. Moderate northwest flow aloft becoming light late tonight and
Monday. Moist in the lower to mid level and somewhat dry in the
higher levels. Air mass will continue to stabilize as the night
progresses...indicated best by the downward trend in shower
activity. Predominately VFR cigs.
A weak Puget Sound Convergence Zone has set up right along the
King/Snohomish county line. This may impact winds at SEA and BFI
with winds switching from east-northeasterly to northerly and
changing in speed from around 5 kts to up to 12 kts through at least
06Z tonight. After 06Z...winds are expected to be generally light at
most locations with speeds generally less than 5 kts.
KSEA...VFR cigs remain in place. PSCZ showers look to be remaining
north of the terminal...but would not rule out a stray light shower
through 06Z. Winds addressed in above discussion. Risk for showers
will continue to diminish through the night with dry conditions
Monday. dtm/SMR
&&
.MARINE...Moderate onshore flow will will decrease behind the trough
later tonight. Gale warning for the strait ended up hitting early
with winds gradually diminishing through the night. Current obs at
Race Rocks show winds well below thresholds...so will likely replace
gale warning with SCA for evening forecast package. Will likely
leave remaining headlines in place...or at least will not re-
evaluate for current issuance. Swell of 11-14 ft and northwest winds
15-25 knots over the coastal waters will also continue through
tonight with a small craft advisory in effect. Winds will ease over
the coastal waters Monday but hazardous seas of 10-12 feet will
persist.
High pressure will be centered over the waters on Monday and Monday
night, leading to weak gradients and light wind. A weak warm front
will bring increasing wind Tuesday and a weak cold front arrives
late Wednesday. dtm/SMR
&&
.HYDROLOGY...River flooding is not expected for the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Admiralty Inlet-
Central U.S. Waters Strait Of Juan De Fuca-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-East Entrance U.S. Waters Strait Of
Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De
Fuca.
Small Craft Advisory for hazardous seas from 3 AM to 5 PM PDT
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.
Small Craft Advisory for rough bar until 11 AM PDT Monday for
Grays Harbor Bar.
&&
www.weather.gov/seattle
You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.htmlThe national radar mosaic for the moment the first event began.
1 debris flow. Local standard time, as filed.
A small landslide occurred near the town of Oso, WA and SR530 was closed for precaution (4 mile stretch between Oso Loop Road and C Post Road.
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, April 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: 690715.