892
FXUS66 KSEW 232309
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
310 PM PST Sat Nov 23 2024

.SYNOPSIS...An upper-low continues to churn off the Pacific coast
through the start of the new week with active weather persisting.
Conditions will settle by midweek and into the Thanksgiving holiday
as guidance hints at the return drier weather but cooler
temperatures.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Current satellite imagery
not too terribly different from this morning with plenty of clouds
over W WA this afternoon, although there are some holes in the cloud
cover over the southwestern part of the CWA in portions of Grays
Harbor, Mason, Thurston and Lewis counties. Radar showing echoes
focused mainly over the northern halves of Grays Harbor and Mason
counties to points north. Much like this morning, echoes having a
hard time crossing the Sound, although some light ones have found
their way as far as western portions of Whatcom and Skagit counties.

Deterministic and ensemble models remain fairly consistent, keeping
the upper level low wobbling out over the Pacific waters, churning
as it does so. This will bring waves of precip to the area...but
nothing particularly organized per se...instead defaulting to
activity more shower-like than anything else. With the main
highlight of the past week being wind, models continue to suggest
that some increased winds will still be possible early this evening
for locations adjacent to the Strait, the north Sound and the
Northern Interior waters /including western Whatcom and Skagit
counties/. While speeds will be nowhere near the order of magnitude
as yesterday or the windstorm of last Tuesday/Wednesday, speeds up
to 20 mph with occasional gusts up to 30 mph will still be possible
in these areas. Speeds will gradually ease this evening and tonight
with no further wind issues expected for the short term.

Some upper level ridging looks to build into the area for Sunday,
however given the proximity of the aforementioned upper low, this
ridge will not be enough to bring any significant drying to the
area, keeping showers in the forecast. The low finally starts to
push inland Monday however a consensus is emerging that the storm
track may end up being to the south of WA. This would allow for some
drying in the northern third of the CWA Monday with gradually
diminishing PoPs for the remainder of the area throughout the day.
Solutions remain in sync with each other, showing the upper low
finally moving inland Tuesday...with the storm track pulling south
of the area. Ensemble members largely in agreement that a period of
dry weather is expected to start here, though some members are
hesitant to scour out any shower activity just yet.

Daytime highs remain generally in the same ballpark throughout the
short term, ranging in the upper 40s to lower 50s. Overnight lows
will not show much in the way of variance either, ranging in the
upper 30s to lower 40s for most lowland locations.

18

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...A shortwave ridge builds
into the area Wednesday, serving as the leading edge of a larger
ridge centered over the Pacific. Between the two is what could be
construed as a very minor trough if the viewer should squint hard
enough. This feature, to use the loosest definition of the word, has
the potential to bring in some moisture that could result in
showers, however the majority of ensemble members currently favor a
drier solution here...keeping the run up to the Thanksgiving
holiday, as well as the day itself...generally dry. The
aforementioned larger Pacific ridge starts to shift toward W WA for
the remainder of the long term, and this would serve to keep an
uneventful weather pattern over much of the western US. NBM still
clinging to some source of moisture, hence the slight chance PoPs in
the forecast...but only a few stray ensemble members are turning in
solutions that would result in precip. The vast majority favor a
continued dry period.

That said, temps in the long term will cool a few degrees from the
short term, with lowland daytime highs generally in the mid to upper
40s. Overnight lows will show more significant cooling, but again
remaining persistent throughout the period, ranging in the lower to
mid 30s.

18

&&

.AVIATION...Upper level low off Vancouver Island moving southwest
through Sunday. Southwesterly flow aloft over Western Washington.
Air mass moist and somewhat unstable. Showers embedded in
southwesterly flow aloft moving through the area into Sunday.

VFR conditions through Sunday morning with ceilings lowering to MVFR
in heavier showers.

KSEA...VFR conditions through Sunday morning with ceilings.
Showers arriving at the terminal Later Sunday morning lowering
ceilings to MVFR. Ceilings improving back to VFR in the afternoon.
Southerly wind around 10 knots easing to 4 to 8 knots after 04z.
Winds becoming easterly 4 to 8 knots after 09z. Felton

&&

.MARINE...A 995 millibar surface low west of Vancouver
Island will continue to weaken overnight as it drifts slowly south.
The low will drift into the Oregon coastal waters and dissipate
early next week as surface ridging builds over the interior of
British Columbia.

Small craft advisory winds over portions of the coastal waters until
Sunday afternoon. Small craft advisory winds in the Strait of Juan
de Fuca until Sunday afternoon as well.

Seas 7 to 9 feet subsiding slightly Sunday and Monday. Felton

&&

.HYDROLOGY...The Skokomish River crested Saturday morning about
three tenths of a foot above flood stage. The river will recede
barely below flood stage tonight and remain within a half a foot of
flood stage into Monday morning.

For the remainder of the rivers no flooding is expected at this
time. The lack of hydrologically significant precipitation and lower
snow levels into next week will limit runoff and reduce flooding
chances. Felton

&&

.CLIMATE...Through 3 pm there has been no measurable rain at
Seattle-Tacoma airport. If the showers miss the airport the
remainder of the day the consecutive days with measurable rain
streak at the airport will come to an end at 14 days. The last time
there was a streak longer than 14 days was 15 days from January 15
to 29 in 2018. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 6 AM to 1 PM PST Sunday for West
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 10 PM this evening to 1 PM PST Sunday
     for Central U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 4 PM PST Sunday for East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 1 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 Out 10 Nm.

     Small Craft Advisory until 1 PM PST Sunday for Coastal Waters
     From Point Grenville To Cape Shoalwater Out 10 Nm.

&&

$$