Heavy Snow and Winter Weather in Washington, February 14 to 15, 2024

Area Forecast Discussion
National Weather Service Seattle WA
903 PM PST Wed Feb 14 2024

.UPDATE...Precipitation continues to slide northward this evening
associated with a low pressure system offshore of WA/OR. We've
received a few reports so far of rain or rain/snow mix for
southern Puget Sound. The major changes this evening are the
following:

* SNOW: A Winter Storm Warning was issued for Hood Canal due to
  upslope influence tonight into Thursday morning with continued
  easterly winds. HREF suggests approximately 70%+ chances of 4"+
  of snow in this area through Thursday, with slightly lesser
  probabilities on the NBM. Given the T/Td spread at the moment
  for much of the area, expecting periods of steady snow though
  tonight in Hood Canal. Furthermore, issued a Winter Weather
  Advisory for eastern portions of Kitsap County, with the best
  potential for light accumulating snowfall in interior areas,
  mainly towards KPWT.

* WIND: Strong east winds continue near the Cascade gaps this
  evening, with gusts of 45 to 50 MPH observed in Enumclaw. Given
  continued easterly flow and elevated gradients through tonight,
  have issued a Wind Advisory into early Thursday morning. Winds
  will likely be strongest near Enumclaw given a slight southerly
  component, but breezy winds also expected towards North Bend as
  well.

Uncertainty continues for a few other areas in regards to
precipitation type and snowfall amounts with this system.
Particularly the potential for accumulating snowfall for coastal
Grays Harbor County as well as northern Olympic Peninsula.
However, given low confidence have not adjusted the forecast much,
but these areas will need to be monitored for snowfall. JD

&&

.SYNOPSIS...A front will cross the region tonight, bringing in
widespread precipitation, cooler temperatures, and breezy winds
through Thursday night. Wet conditions will linger into Friday,
where a period of a rain/snow mix is possible for the lowlands
early Thursday and Friday mornings. Active weather will continue
through the weekend and into next week as temperatures follow a
warming trend, but no significant impacts are expected beyond
Friday morning.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...A low pressure system
will continue to progress towards the Washington coast this
afternoon and evening, tightening the pressure gradient and
maintaining breezy Fraser River outflow winds. This will also
enhance mountain gap winds with gusts to 40-45 mph through the
mountain passes.

A front will continue to lift across the region this evening,
spreading precipitation northward across western Washington into
Thursday morning. Cooler air will filter in and cause snow levels
to lower to 400-500 ft overnight tonight. For much of the lowlands
east and north of the Puget Sound, overnight low temperatures will
bottom out slightly above freezing, allowing precipitation to
fall as a cold rain or rain/snow mix with minimal accumulations.
Temperatures will warm Thursday morning, shifting precipitation
back to rain and melting any accumulations that do occur quickly.

Elsewhere over the Hood Canal and Kitsap Peninsula, cold air
enhanced by damming and upslope from the Olympics will create
more favorable conditions for snow accumulation. Ensembles
maintain a moderate (50 to 60 percent) chance of at least an inch
of snow accumulation through Thursday morning for these areas
along with parts of the Chehalis Valley and southern Puget Sound
lowlands south of Olympia. A Winter Weather Advisory remains in
effect across these areas through Thursday morning for up to 3
inches of snow which may cause slippery travel conditions during
the morning commute. Snow amounts may be locally higher for areas
of Kitsap west of Bremerton, where some ensembles show a chance
(30 percent) to 5 inches of snow accumulation.

While precipitation will lighten throughout the day Thursday over
the lowlands, the surface low will meander along the coast and
focus the bulk of the continued moisture fetch over the Cascades
from Mount Rainier southward. Areas including Paradise at Mount
Rainier and White Pass along Highway 12 are on track to see
roughly 15 inches of snow accumulation tonight through Thursday
evening. A Winter Weather Advisory for the southern Cascades of
Pierce and Lewis Counties will continue through Thursday evening
for snowfall totals of 12-15 inches that may cause difficult
travel conditions.

Low pressure will shift westward Thursday night as weak ridging
amplifies towards western Washington. This will strengthen the
gradient and maintain breezy easterly winds. Another wave of
moisture will lift across western Washington, maintaining the
threat of more lowland mixed precipitation and higher elevation
snowfall. Temperatures across the lowlands will be even cooler
overnight into Friday morning, but the Seattle metro maintains a
low (20 to 30 percent) chance of falling below freezing. This will
minimize travel impacts for lowlands around the Sound, but colder
air in place across the Hood Canal area and Chehalis Valley may
allow for a brief round of additional light snowfall accumulation.
Light snow will also accumulate over the mountains, though amounts
will be light.

Weak ridging will build northward into the region on Friday,
allowing conditions to briefly dry out. Temperatures will
also warm up several degrees, peaking above the 50 degree mark
across the lowlands on Friday afternoon. Another round of
widespread precipitation will begin to move onshore late Friday
into Saturday as a deep low progresses towards the coast. Warmer
conditions will allow snow levels to stay above 3500 ft, resulting
in more lowland rain and mountain snow.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Active weather will
stretch into Sunday as the first in a series of frontal systems
pushes onshore. Medium range models and ensembles continue to show
a strong Pacific system moving into California, hinting at warmer
pattern with marginal wrap around moisture for much of the
Pacific Northwest into the middle of next week. The forecast
continues to reflect a warming trend through the long-term with
temperatures staying in the 50s across the lowlands and snow
levels to stay at or above 4000 ft, confining snowfall to higher
terrain of the Olympics and Cascades.

&&

.AVIATION...West to southwesterly flow into Thursday with an upper
low offshore of WA and OR. Offshore flow continues at the lower
levels. Precipitation continues to slide northward this evening
with rain or rain/snow observed as far north was PWT as of 9PM.
This will continue to move northward tonight, with a rain/snow mix
possible at most locations, particularly south Skagit County
southward. The best potential for accumulating snowfall is along
Hood Canal and towards the Kitsap Peninsula. Cigs will continue to
lower in areas of precipitation towards MVFR/IFR tonight into
early Thursday. Vsby reduction may occur as well with
precipitation. Shower activity will taper off later Thursday with
some improvement to cigs. Breezy east winds continue at the
surface.

KSEA...VFR cigs this evening continue to lower towards MVFR.
Precipitation likely to begin between 06-08z as a rain and snow
mix, with the potential to transition to snow late tonight into
early Thursday morning. Although uncertainty does exist in
precipitation type, at this time accumulations are not expected.
However, snow in the air may reduce slantwise and surface
visibilities. Showers return Thursday morning before tapering on
Thursday. Breezy east winds continue tonight, with sporadic gusts
of 20 to 30 kts possible. JD

&&

.MARINE...Offshore gradients will increase today as a 1000
mb low approaches the waters. The low will track northward into
the coastal waters tonight and weaken before dissipating Thursday.
Offshore gradients will continue Friday with a frontal system
moving inland Saturday.

Small craft advisories remain in place for easterly winds in the
Northern Inland Waters, the Strait of Juan de Fuca, and the
Coastal Waters into Thursday night. Possible gales over the coastal
waters Friday as a frontal system approaches, although with
easterlies continuing, confidence is lower on this outcome. Seas
building to 10 or 11 feet late Thursday afternoon into Thursday
evening with the seas subsiding below 10 feet Friday.

Kristell

&&

.HYDROLOGY...No river flooding is expected over the next seven
days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 10 AM PST Thursday for Bremerton
     and Vicinity-Lower Chehalis Valley Area-Southwest Interior.

     Winter Storm Warning until 10 AM PST Thursday for Hood Canal
     Area.

     Winter Weather Advisory until 1 PM PST Thursday for Olympics.

     Wind Advisory until 7 AM PST Thursday for East Puget Sound
     Lowlands.

     Winter Weather Advisory until 10 PM PST Thursday for West Slopes
     South Central Cascades and Passes.

PZ...Small Craft Advisory until 4 AM PST Friday for 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-Northern Inland Waters Including The San Juan Islands-
     West Entrance U.S. Waters Strait Of Juan De Fuca.

&&