Winter Storm Warning 5, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
220 AM PST Sat Feb 26 2022

.SYNOPSIS...Precipitation from an incoming system is expected to
begin late this morning for the coast before moving inland
throughout the day. This system will bring lowland rain, mountain
snow, and windy conditions to Western Washington. A second system
will impact the area starting Monday. Weather will remain active
through the rest of the week.

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.SHORT TERM /TODAY THROUGH MONDAY/...A return to active weather
begins today as a weather system continues to move inland. As the
system moves inland southerly winds will be increasing throughout
the day. A High Wind Warning has been issued for the San Juan,
Island and Northeastern Jefferson Counties, expect gusts up to
50 mph. Wind advisories have been issued for the coast as well as
Western Whatcom and Skagit counties where gusts of 40 mph are
expected. For the rest of the lower elevation areas of Western
Washington expect gusts 15-25 mph. Tree and power line damage is
possible, especially for areas under the warning and advisories.
Winds throughout the region are expected to ease late Saturday.

Precipitation from this system is expected to begin at the coast
by late this morning and move inland by late this afternoon.
Snow levels are expected to increase to 3000-3500 feet for the
Olympics and Cascades as this system moves through. Snowfall
accumulations are expected to be the greatest in the Western
Olympics where 1-2 feet of snow (at high elevations) is expected
by Sunday morning. The North Cascades are expected to see the
second highest accumulations of 1-1.5 feet expected. But
accumulation rates are expected to be slower in this region. The
greatest accumulations will be at higher elevations. For
reference, Stevens and Snoqualmie Passes will likely see 4-8
inches over a 24 hour period, with Stevens likely experiencing
the higher end of snow accumulations.

Conditions will ease slightly Sunday, but showers will remain in
the area, which will lead to additional snow accumulations in the
mountains. This relatively quieter weather will be short lived as
an atmospheric river (AR) is forecasted to impact the region
Monday.

This AR will bring more lowland rain and mountain snow to the
area. This is likely to prompt its own winter weather advisories
and warnings for the mountains. As the AR continues to impact the
region, snow levels will rise above the passes. Area rivers are
expected to respond to this AR, see hydrology section below for
more details.

Butwin

.LONG TERM /TUESDAY THROUGH FRIDAY/...Precipitation from the AR
will gradually taper off throughout the day Tuesday. Weather will
remain unsettled through the rest of the week as an upper level
trough slowly moves over the area. While precipitation is not
expected everywhere everyday, it will remain cloudy and damp.
Certainly a reminder that winter is not done quite yet.

Butwin

&&

.AVIATION...High level cloud cover continues to stream into the
region this morning from off of the Pacific, resulting in an
overcast deck around 20-25kft. These clouds are associated with the
next frontal system that should push across the area later today.
The trend will be for gradually lowering ceilings today, with rain
spreading in from west to east. By this evening, most sites should
drop from VFR ceilings to MVFR, with some vsby reduction possible.
South winds through the period, 8-12 kts today, increasing overnight
and early Sunday, with gusts 20-25kts likely.

KSEA...Cloud lowering from VFR to MVFR later this afternoon/evening
as rain spreads in. Rain will taper to widely scattered showers
Sunday. S/SE winds 8-12kts today, picking up tonight and early
Sunday to 10-15kts with gusts up to 25kts possible.

Kovacik

&&

.MARINE...High pressure over the inland NW will gradually be
replaced by lower pressure today as a frontal system approaches. In
response to the front, southerly winds will begin to increase in the
next few hours, especially over the coastal waters and northern
interior waters. Hi-res model guidance has been consistent in
showing persistent gale force winds for these areas after 12z this
morning, lending high confidence in this forecast scenario. Perhaps
the only recent thing of note is the potential for a period of winds
40-45kts through the East Entrance up towards the San Juan Islands
during the afternoon hours today. Elsewhere, remaining waters should
experience SCA level winds with this system.

Winds will gradually ease through the morning hours Sunday, however,
this looks to be short-lived as the next system, similar in strength
to today's, begins to approach the area. There will likely be
another round of gales for at least the coastal waters. Thereafter,
an active weather pattern will continue through the remainder of the
week, although winds currently do not look as strong as previous
systems.

Swells will begin to increase this afternoon and should reach 10
feet this evening. Seas will then gradually subside through the day
on Sunday before increasing again on Monday in association with the
next system.

Kovacik

&&

.HYDROLOGY...With two weather systems moving through the area this
weekend/early next week, area rivers are expected to respond. But
due to the recent stretch of relatively dry weather, many rivers
are currently sitting well below action stage. So even with these
two systems, most Western Washington rivers are expected to remain
below flood stage. That said, currently the Skokomish and
Snoqualmie (at Carnation) Rivers are forecasted to reach minor
flood stage late Monday/early Tuesday. Confidence in the
Snoqualmie River reaching flood stage is currently low.

Butwin

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory from 4 PM this afternoon to 1 PM PST
     Sunday for Cascades of Whatcom and Skagit Counties.

     Wind Advisory from 4 PM this afternoon to 8 AM PST Sunday for
     Admiralty Inlet Area-Eastern Strait of Juan de Fuca-San
     Juan County-Western Skagit County-Western Whatcom County.

     Wind Advisory from 10 AM this morning to 4 AM PST Sunday for
     Central Coast-North Coast.

PZ...Small Craft Advisory until 4 AM PST early this morning 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 Warning until 4 AM PST Sunday 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-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 Sunday for West Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 4 AM PST Sunday for Admiralty Inlet-
     Central U.S. Waters Strait Of Juan De Fuca-Puget Sound and
     Hood Canal.

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