Washington State Forecast Discussion

Western Washington


344
FXUS66 KSEW 201047
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
247 AM PST Fri Dec 20 2024

.SYNOPSIS...A series of fronts will bring several rounds of light
precipitation into tomorrow, with breezy winds and slightly warmer
temperatures. A more active pattern is set to evolve and take
shape this weekend and last into next week, with an increased
chance of impactful weather arriving during the holidays.


&&

.SHORT TERM /TODAY THROUGH SUNDAY/...Showers have largely tapered
early this morning as shortwave ridging evolves and will keep
things drier through the morning hours. The next front will arrive
early in the afternoon and bring back precipitation to the area.

The weekend will be damp, with a few frontal systems moving
through. On Saturday, expect some breezy east winds through the
Cascade gaps in the morning, although high wind is not
anticipated. South winds will resume Saturday afternoon but will
not be particularly strong. Highs over the weekend will be
slightly warmer than average with afternoon highs in the 50s and
lows in the 40s. Snow levels will lower somewhat on Sunday for
light accumulations at the passes.

.LONG TERM /MONDAY THROUGH THURSDAY/...The pattern activity is
expected to amplify into next week, with additional systems
expected around the holidays. Probabilities in increased
atmospheric river activity accompanying these frontal systems have
increased as well. A stronger atmospheric river is possible by
midweek, lingering into Thursday with higher integrated water
vapor values, suggesting more rain and snow in the Cascades and
Olympics. In addition to heavy rain at times, there will be
periods of stronger winds. The CPC outlooks suggest a moderate
risk (generally 40 to 60 percent chance) of heavy rain and
mountain snow. The potential exists for implications to busy
holiday travel, but it is still somewhat early to get an
indication of what those will be, but this will be refined as more
is known about the storms on their way in the coming days.

Kristell


&&

.AVIATION...Southwest flow aloft will develop this
morning as upper level trough digs south offshore and warm front
moves by to the west of the area. Offshore flow will continue at the
lower levels with E/SE winds generally 5-10 kt.

Mainly VFR as cloud cover increases this morning, with areas of fog
and low stratus lingering across the Chehalis Valley and along the
Strait of Juan de Fuca. Shower activity will lift northward later
this morning, with brief MVFR conditions in showers. Conditions will
dry from the west through the afternoon and evening hours as showers
diminish. Drying overnight will give way to some fog development
that may impact the southern terminals Saturday morning.

KSEA...VFR ceilings through Friday, with brief MVFR conditions in
showers that develop today. Winds generally E to SE 4 to 8 kt
through the period.

15


&&

.MARINE...A series of fronts will cross the region over the next
several days, maintaining seas above 10 feet and periods of breezy
conditions through the weekend and into next week. A Small Craft
Advisory remains in effect for the coastal waters through the early
morning, which will continue through the afternoon for the inner
coastal waters and Eastern Strait of Juan de Fuca, and will be
replaced by a Gale Warning for the outer coastal waters. SCA
conditions will continue overnight into Saturday morning, with
potential Gale conditions developing later Saturday morning and into
the afternoon as a front once again brings in gusty winds over the
outer waters and maintains elevated seas.

Combined seas this afternoon 10 to 13 feet. Seas will then build
upwards to 15 to 19 feet Saturday and are favored to stay elevated
in the 15 to 25 foot range through the weekend and into early next
week. Seas are favored to ease briefly to 12 to 15 feet Tuesday
night into Wednesday before another round of elevated seas 17 to 21
feet the second half of next week.

15


&&

.HYDROLOGY...Additional incoming precipitation later this week looks to remain
light with only minor rises on area rivers expected. The Skokomish
River will continue to recede, but remain in the vicinity of flood
stage the next few days. The threat of river flooding across western
Washington will increase again mid to late next week, with ensembles
showing the potential for significant precipitation to return. While
discrepancies remain, this may cause an increasing chance of river
flooding and landslide concerns that may impact holiday travel.


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 6 AM this morning to 3 PM PST this
afternoon for West Entrance U.S. Waters Strait Of Juan De
Fuca.

Small Craft Advisory until 4 AM PST Saturday for Coastal Waters
From Cape Flattery To James Island Out 10 Nm-Coastal Waters
From James Island To Point Grenville Out 10 Nm-Coastal
Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Gale Watch from late tonight through Saturday afternoon 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.

Small Craft Advisory until 6 AM PST early this morning 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.

Small Craft Advisory from 3 PM this afternoon to 4 AM PST
Saturday 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.

Gale Warning from 6 AM this morning to 3 PM PST this afternoon
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.

&&