Gale Warning 3, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
830 PM PST Sun Jan 7 2024

.UPDATE...A few very isolated showers along the coast linger with
reduced activity in the Cascades. The forecast is still largely on
track with quite the lineup of incoming headlines for more active
winter weather starting tomorrow. Additionally, there is a slight
chance that at the onset of the precipitation in the morning,
combined with low temperatures in the low to mid 30s, that things
could initially start as a rain/snow mix. The favored areas would be
near Hood Canal and generally from Everett northward, but it may
occur in isolated pockets elsewhere before rain takes over in the
lowlands. Stay tuned to the forecast for updates as the activity
continues into the late week period. /Kristell

&&

.SYNOPSIS...An active weather pattern brings heavy mountain snow,
lowland rain, strong winds, and possible coastal flooding through
midweek. Cooler conditions develop for the latter half of the week
bringing a threat of lowland snow.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...A very active week of
weather for western WA and the Pac NW. A list of hazards include:
Heavy snow and blizzard conditions in the mountains, heavy rain in
the lowlands, strong winds, river flooding (Skokomish) and possible
coastal flooding.

The next incoming system will bring heavy snow in the mountains on
Monday with up to a foot of new snow. Snow levels will be higher
along the south slopes of the Olympics and heavy rain will force
sharp rises on the Skokomish River in Mason county. Minor flooding
is possible Monday night or Tuesday.

The following, stronger, system will move in Monday night into
Tuesday as a deep (970-975 mb) low shifts toward Vancouver Island.
This system will bring strong, widespread winds with gusts to 40-50
mph across most areas. Winds may be stronger along the coast and
Strait of Juan de Fuca. Strong winds will also impact the mountains
with gusts to 50-60 mph as well. Strong winds combined with heavy
snow will create blizzard conditions in the mountains with reduced
visibility in blowing snow. Strong onshore flow will persist Tuesday
night into Wednesday and the mountains will see an additional 1 to 5
feet of snow. Down in the lowlands, more rain on tap with storm
total rainfall amounts around 1-2". The highest amounts will be
along the coast. Meanwhile, as this system churns offshore, seas
will build with large swells reaching our coast - high surf
conditions possible.

Strong mountain winds and heavy snow continues into Wednesday with
snowfall rates decreasing toward the afternoon (as winds ease). Seas
will subside but we will also see high tides and possible minor
tidal overflow with King tides. We'll definitely look closer at
contributing factors to tidal anomalies like low pressure and winds.
33

.LONG TERM /THURSDAY THROUGH SUNDAY/...The air mass cools further
as we head toward the latter half of the week with northerly flow
aloft and brief offshore winds. Strong Fraser River outflow winds
may develop over the north interior with high pressure over interior
B.C. The focus then shifts to how cold we get and the potential for
lowland snow. There is still a lot of uncertainty in how cold we get
based on the ensemble spreads. However, even lows in the 20s (most
likely scenario) is much below normal and cool enough for snow. So
with cool temps and low snow levels there is a threat of seeing some
lowland snow Wed night through Saturday. There's at least a 30-40%
chance of seeing 1" or greater, but seeing significant amounts of 4"
or greater is generally 10% or less. If any one period stands out it
would be Friday night into Saturday as a wetter system moves in. We
could see a scenario of snow turning over to rain and where/when
this changeover occurs is always tricky thus keeping a rain/snow mix
in the forecast. Snow levels remain marginal on Sunday for a
rain/snow mix as well. 33

&&

.AVIATION...Northwest flow aloft over the region will transition
more to westerly flow on Monday as an upper trough moves towards the
area. Lingering light rain around Puget Sound but most areas dry
this evening with VFR/MVFR cigs. A warm front will approach the area
into Monday morning with increasing rain and lowering cigs through
tonight. Generally widespread MVFR cigs late tonight into Monday
with areas of IFR, and patchy LIFR along the coast. Rain will
increase for the area late tonight through Monday morning. A brief
rain/snow mix cannot be ruled out for KBLI in particular Monday AM,
but generally rain expected for the area. Cigs will remain
persistent MVFR/IFR through Monday. Light winds this evening will
increase S/SE into Monday morning.

KSEA...MVFR cigs this evening may briefly go VFR at times between 05-
09z. Otherwise, cigs will continue to remain MVFR after 09z and
through Monday morning. Rain will increase generally between 09z-12z
and continue through Monday. MVFR cigs on Monday with at least a 25%
chance of IFR cigs on Monday as well. Surface winds will transition
from more light NE to increasing S/SE later tonight into Monday.
JD

&&

.MARINE...The next round of winds increase as the warm front lifts
across the area tonight into Monday. A more significant period of
weather impacts arrives late Monday night and especially Tuesday as
a deep surface low, down into the 975 mb range, tracks north toward
Haida Gwaii. This will likely lead to widespread gales across the
waters, both southerly ahead and westerly behind. Gale Watch
continues for all waters except Puget Sound and anticipate an
upgrade on this as the next cycle of guidance some in and allows the
timing to be refined. Small Craft also issued for the eastern Strait
of Juan de Fuca and Admiralty Inlet for increasing southeast winds
on Monday. Confidence remains rather high for a lengthy period of
gales with this strong system as it passes, and the potential for
local storm force gusts through the Strait of Juan de Fuca late
Tuesday. Ensemble guidance continues to suggest a high likelihood
(60+% chance) of seas building above 25 ft over the coastal waters,
adding another layer of impacts to the storm. JD

&&

.HYDROLOGY...Heavy rainfall of 2-4 inches in the Olympics associated
with a strong frontal system will lead to sharp rises on streams and
rivers. The Skokomish River in Mason County is forecast to rise into
Minor Flood Stage late Monday night or Tuesday morning. No other
river flooding is forecast over the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through Tuesday morning for Hood Canal Area-Lower
     Chehalis Valley Area-Olympics.

     Winter Storm Warning from 7 AM Monday to 4 AM PST Tuesday for
     Olympics-West Slopes North Cascades and Passes-West Slopes
     North Central Cascades and Passes-West Slopes South Central
     Cascades and Passes.

     Blizzard Warning from 4 AM Tuesday to 10 AM PST Wednesday for
     Olympics-West Slopes North Cascades and Passes-West Slopes
     North Central Cascades and Passes-West Slopes South Central
     Cascades and Passes.

PZ...Small Craft Advisory until midnight PST tonight for Grays Harbor
     Bar.

     Gale Watch from late Monday night through Tuesday evening for
     West Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Watch from Monday evening through late Tuesday night 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 from 7 AM to 10 PM PST Monday for Admiralty
     Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 4 PM 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.

     Gale Watch from Monday afternoon through Tuesday 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.

&&