691
FXUS66 KSEW 231744
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
944 AM PST Mon Dec 23 2024

.UPDATE...A pleasant start to the day with mostly clear skies and
temperatures in the mid to upper 40s across western Washington.
Take in the sunshine while you can, as clouds will increase later
this morning into this afternoon as the next system moves into the
area. Winds will also begin to increase tonight. The forecast
remains on track, with the updates to the discussion below. 62

&&

.SYNOPSIS...The active pattern continues with multiple frontal
systems moving through the area bringing periods of rain, mountain
snow, and gusty winds. The focus shifts towards Christmas into
late next week with potentially higher-impact systems with heavy
rain and snow and gusty winds, especially when combined with
holiday travel.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...Today will feature a
somewhat longer reprieve from more active weather, with the next
front arriving tonight into Tuesday morning. Right now, scattered
showers linger along the Olympic Peninsula and in the Cascades.
This will largely taper off into the late morning hours. Expect
partly cloudy conditions with a high in the low 50s today.

Going forward into Tuesday, the next storm will arrive and bring
another round of rain and stronger winds. Wind direction will be
out of the east to southeast for much of Tuesday morning before
transitioning to southerly as the frontal system gets nearer to
the coast. Cascade gaps, northern Olympic Peninsula and immediate
coastal locations will see the strongest winds. Right now, the
forecast calls for gusts in these locations to be between 35 and
40 mph through late Monday night into early Tuesday morning.
Precipitation should become more scattered by Tuesday evening.

Tuesday night will be more quiet, but the next, more substantial
system will arrive on Wednesday. The storm on Wednesday has more
of an atmospheric river profile, and will contain much more QPF
than the previous few systems. The highest rainfall totals will be
over the coast and Olympics for around 3 to 4 inches of rain with
locally higher amounts. An inch to one and a half inches is likely
for the lowlands. Consequentially, snow levels will lower to
around 3000 feet over the Cascades, causing heavy snow at all of
the passes. Wind will again pick up late Wednesday morning from
the south, with the windiest locations being the eastern Strait of
Juan de Fuca, northern Puget Sound and Salish sea and along the
immediate coast.

Building waves along the coast will create multiple periods of
high surf conditions Monday through Wednesday. Initial rounds of
high surf will have longer periods and cause further run up on
beaches, with the next few rounds causing breakers Tuesday and
Wednesday.


.LONG TERM /THURSDAY THROUGH SUNDAY/...Wet weather continues on
Boxing day and beyond as more systems move into the PNW. Heavy
mountain snow, moderate to heavy rain and breezy winds are all
expected into the long term period of the forecast. Another round
of seasonably higher tides in this timeframe will need to be
monitored, as coupled with more storms there could be coastal
flooding and erosion impacts.

Kristell


&&

.AVIATION...West flow aloft with weak high pressure briefly shifting
over the region. Another front approaches late today bringing a
return of stronger southwesterly flow. A few lingering patches of
fog in the southern interior portions around KOLM and KCLS will be
short-lived this morning. VFR conditions remain elsewhere and
otherwise today, with increasing high and mid clouds through the day
ahead of the front. Expect gusty east winds to develop through the
Cascade gaps this evening, with gusty southerly flow developing
ahead of the front early Tuesday with the strongest winds near the
coast. Meanwhile, expect lower ceilings and reduced visibility in
rain to reach the coastline toward 03z tonight and pushing into the
interior by 06-09z.

KSEA...VFR conditions with light wind this morning. Increasing high
and mid clouds with dry conditions for the afternoon with another
round of rain reaching the terminal after 06Z Tuesday. Surface winds
becoming east/southeast later this afternoon and becoming gusty,
before returning to southerly overnight. 12

&&

.MARINE...Easterly gradients will tighten during the day today
as a surface low deepens to around 980 millibars 400 nautical miles
west of Hoquiam by the late afternoon. It is expected to continue to
deepen to sub 970 millibars as it lifts northeastward toward Haida
Gwaii Monday night. This will push an occluded front across area
waters early Tuesday. Gales are expected with this front across the
coastal waters and near the entrances to the strait with small craft
advisory conditions across all other waters.

A secondary system will quickly follow on its heels Christmas
night into Boxing Day. Similarly, this system also has strong
potential to produce another round of gales (or stronger) for the
coastal waters and strait entrances. This pattern is expected to
persist into next weekend as a series of vigorous fronts and
strong surface lows impact the waters. Seas look to remain quite
hazardous for the foreseeable future with wave heights over the
coastal waters remaining in the 15 to 20 foot range much of the
time.

27/15

&&

.HYDROLOGY...A series of frontal systems will move through western
Washington next week and bring several rounds of precipitation. The
most hydrologically significant system will be the atmospheric river
arriving Christmas into Thursday, with few breaks in the
precipitation late week into next weekend.

The Skokomish river has receded from moderate to minor flood stage
this morning. This recession could be fairly short lived as the next
round of rain arrives Monday night into Tuesday and continues
thereafter as more systems arrive. Another rise into moderate flood
is possible by Thursday.

Other area rivers in the southwest interior such as the Chehalis and
Newaukum are forecast to reach moderate flooding with as much QPF
that is expected. Additionally, a handful of Cascade basins and
rivers are showing potential for at least action stage but will need
to be monitored. All of the precipitation also carries an increased
risk of landslides which, if they occur, have the potential to
impact holiday travels.

Kristell/McMillian

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...High Surf Advisory until 9 PM PST this evening for Central Coast-
     North Coast.

PZ...Small Craft Advisory until 4 AM PST Tuesday for Grays Harbor Bar-
     West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 4 AM PST Tuesday for Central U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning from 4 PM this afternoon to 7 AM PST Tuesday for
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 4 PM this afternoon to 7 AM PST
     Tuesday for Admiralty Inlet-Northern Inland Waters
     Including The San Juan Islands.

     Small Craft Advisory from 7 PM this evening to 7 AM PST Tuesday
     for Puget Sound and Hood Canal.

     Small Craft Advisory until 4 PM PST this 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.

     Gale Warning from 4 PM this afternoon to 4 AM PST Tuesday 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.

&&

$$