Brier Weather Station

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 Latitude N 47° 46' 49"    Longitude W 122° 16' 48"    Elevation 341 ft

445
FXUS66 KSEW 132213
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
213 PM PST Thu Feb 13 2025

.SYNOPSIS...A frontal system will move through Western Washington
tonight, bringing snow to southwestern Washington and a rain/snow
mix elsewhere. A wet pattern is expected to continue through the
weekend and early next week as several rounds of weather systems
are expected to move trough the region, bringing lowland rain and
mountain snow.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...Radar and satellite
imagery showing a band of precipitation working its way north from
Oregon into southern Washington. There is quite a bit of dry air
at the surface due to the gusty easterly winds that occurred last
night and this morning, with dewpoint depressions ranging from 20
to 35 degrees. As such, it is taking some time before
precipitation is actually reaching the surface. As of 2PM, snow
has accumulated from Pierce County southward to Lewis County.
Prepare for rapid changes in visibility and road conditions as the
snow comes down.

Breezy easterly winds are continuing this afternoon but will
begin to ease this afternoon, with the wind advisory for the East
Puget Sound Lowlands set to expire this evening.

The aforementioned northward-moving band of snow will move
northward this afternoon with light accumulations expected from
Tacoma southward. This band will begin to fall apart as it moves
northward towards the Seattle area this evening, with very light
to no accumulations expected this evening through the northern
half of the region. This, and the easing easterly winds, will
prime the atmosphere for the next round of precipitation that
will arrive overnight into Friday morning. This will be coming
from the west as the back edge of the system moves inland. Here we
will have the best chance for seeing some accumulations,
particularly through the Southwest Interior and the Cascade
foothills. Surface temperatures look to be quite close to freezing
but hover just above freezing, so any snow that falls will be
quite wet and mixed in with rain as well.

Through Friday morning, there remains a 50-80% chance of
seeing 1 inch of snow in areas south of Tacoma and east of
Aberdeen through the Southwest Interior, as well as the Cascade
foothills. The Seattle metro area and Kitsap Peninsula only has a
30-40% chance of 1 inch of snow, with probabilities near 0% north
of Snohomish County, along the Pacific Coast, and along Strait of
Juan de Fuca.

There is a slim chance (20-40%) of some isolated pockets of
freezing rain in southwestern Washington, particularly through the
higher elevations of Lewis and Grays Harbor counties south of US
12 and west of I-5 where temperatures tonight look to hover just
below freezing. Significant icing is not expected in these areas,
especially as other precipitation types will likely be mixed in
through the overnight period.

Showers will move inland and taper off Friday morning. Showers may
linger over the mountains with upslope flow as the winds return to
onshore, otherwise mostly dry conditions will prevail Friday
afternoon and evening. Snow levels will rise to around 1000 to
1500 ft by Friday afternoon. Temperatures will also warm into the
low to mid 40s on Friday. Lows will be in the low to mid 30s.

The next frontal system will move into the region Saturday
afternoon with showers persisting through Sunday. This system will
be much warmer with snow levels returning to the 3000 to 3500 ft
range. Overall the QPF forecast has been trending lighter with
this system, so significant hydrologic impacts are not expected at
this time, though small rises on rivers due to lowland snowmelt
is possible. Significant mountain snowfall at the passes is
expected, with around a 45 to 55% chance of seeing at least 8" of
snow at Stevens and Snoqualmie Passes by Sunday afternoon.

.LONG TERM /MONDAY THROUGH THURSDAY/...Extended models are
showing good agreement in the long-term for the warmer and wet
pattern extending into next week. There may be a break in the
precipitation on Tuesday, particularly for the interior, before
the next system arrives mid-week next week. Highs next week will
be in the upper 40s to near 50, with lows in the upper 30s to near
40. Snow levels look to remain in the 3000-3500 range next week,
meaning additional chances for accumulating snow through the
mountain passes.

62

&&

.AVIATION...An organized low off the coast of OR will continue to
move inland along the WA/OR border tonight into Friday. Expect the
flow aloft to switch from southwest to northwest.

An occluded front to the south has lifted snow showers into the
southern terminals this afternoon (as of 21Z light snow has been
reported in Olympia and Hoquiam with visibilities between 3/4 and 2
SM). The drier air over northern Puget Sound/areas north may limit
some of the precipitation from reaching the ground/accumulating (
warmer temperatures to the north will lead to a rain/snow mix for
areas north of Olympia). Mid to high level ceilings will remain for
areas that do not see precipitation this afternoon tonight.
Otherwise, ceiling and visibility reductions are expected with some
of the heavier precipitation bands that move up from the occluded
front. Gusty winds out of the east/northeast will also diminish
going into the afternoon/evening (windiest terminals have been
coastal areas and sites closest to the slopes of the Cascades).

More precipitation is expected tonight/Friday morning with wrap-
around moisture from the low moving inland, bringing more rain/snow
mix for most terminals south of Whatcom County. Ceilings will
decrease to MVFR as a result, with a few spots potentially seeing
IFR ceilings Friday morning (South Interior and over Puget Sound
waters, as well as Cascades/Olympics). Areas that receive IFR will
have conditions improve to MVFR later Friday morning. Winds will
become light out of the southwest during the day Friday, and onshore
for some coastal areas.

KSEA...Rain/snow showers have arrived this afternoon. Brief
visibility reductions are possible if any heavier band tracks over
the terminal. Otherwise, precip rates are expected to remain light
with this first round of precipitation. Another round of rain/snow
mix is expected late tonight into Friday morning. Probabilities for
an inch of snow at SeaTac remains 30% between 18Z Thur - 18Z Fri.
Expect ceilings to drop to MVFR Friday morning and remain MVFR for
the day. Gusty northeast winds at 8 to 12 kt (with gusts to 20 kt)
will drop to around 5 to 10 kt tonight into Friday, and transition
to the southwest late Friday morning.

HPR

&&

.MARINE...A low off the coast of OR will move inland tonight into
Friday, with increasing pressure gradients. Gusty winds continue
over parts of the Strait of Juan de Fuca and Coastal Waters - will
leave the current small craft advisories up, but expectation is for
winds to decrease over these areas this evening. Rain/snow showers
will continue over portions of the interior and coastal waters this
afternoon into Friday morning (which may reduce visibilities at times
for mariners). The outer coastal waters will continue to see seas up
to 10 ft into Friday afternoon (before dropping back to 7 to 9 feet
into Saturday morning.

Once the low passes, the flow will flip back to onshore/northerly
with lighter winds expected on Friday. Another disturbance Saturday
will flip winds back to the south, and bring gusty winds over the
coastal waters and west/east portions of the Strait of Juan de Fuca.
At this time, the probability of gale wind gusts is very low (less
than 10%), but may change as hi-res guidance becomes available. Seas
will rise up to 8 to 11 feet Saturday into Sunday, and increase
again to 10 to 14 feet Monday before decreasing under 10 feet
Tuesday.

HPR

&&

.HYDROLOGY...No river flooding is expected in the next 7 days.


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 8 AM PST Friday for East Puget
     Sound Lowlands-Hood Canal Area-Lower Chehalis Valley Area-
     Southwest Interior-Tacoma Area.

     Wind Advisory until 5 PM PST this afternoon for East Puget Sound
     Lowlands.

PZ...Small Craft Advisory until 10 PM PST this evening for Central
     U.S. Waters Strait Of Juan De Fuca-Coastal Waters From Cape
     Flattery To James Island Out 10 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 until 7 PM PST Friday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.

&&

$$

NWS SEW Office Area Forecast Discussion

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