Heat in Washington, December 25 to 31, 2023

Area Forecast Discussion
National Weather Service Seattle WA
917 PM PST Sun Dec 24 2023

.SYNOPSIS...A front will continue to weaken across the area this
afternoon. A stronger system will impact Western Washington Monday
into Tuesday for lowland rain, locally gusty winds, and a mountain
wintry mix. Another system will move through Wednesday into
Thursday, with the active pattern continuing into late week.

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.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...The first front from
this afternoon has dissipated with the showers mostly having
pulled off to our north. Skies have cleared for a brief bit too
before additional clouds move in quickly tonight ahead of the
next frontal system. Some light snow continues off an on at the
passes according to latest observations. The main updates this
evening were to refresh winds and the expansion of the Wind
Advisory into western Whatcom and Skagit Counties with latest HREF
and NBM guidance bringing wind gusts up just a touch. With lots of
holiday decorations out as well, opted to go ahead and expand it.

Winds are relatively breezy for portions Admiralty Inlet and
towards San Juan Islands this afternoon, with southeast wind gusts
25 to 40 MPH. Winds will only briefly subside in these areas
tonight ahead of the next frontal system. The next system will
approach Western Washington late tonight and impact the area
Monday through Tuesday. Precipitation for the lowlands will be
rain, with the heaviest amounts over the Olympic Peninsula. The
forecast is a bit more tricky for the Cascade Passes given
continued easterly flow, and cold air entrained into these areas.
The freezing rain potential exists for the Cascade Passes,
particularly Snoqualmie Pass, and the western crest of Stevens
Pass. Precipitation will also mix with snow at times, and perhaps
brief periods of rain and snow. For this reason, a Winter Weather
Advisory was issued from Monday morning through Tuesday morning.
For those traveling over the Passes, check with WSDOT for the
latest Pass conditions. In addition, southeast winds will increase
Monday morning and continue to remain gusty into Monday night for
the northern coast, eastern Strait of Juan de Fuca, Admiralty
Inlet, and San Juan Islands. A Wind Advisory is in effect for
these areas with gusts generally 40 to 50 MPH. Winds will likely
also then increase Monday evening into Monday night elsewhere,
especially along the southern WA coast, and western Whatcom/Skagit
Counties.

The front will generally move out of the area midday Tuesday into
Tuesday afternoon for perhaps a few lingering showers, but
generally drier conditions. A warm front will the move northward
Tuesday evening into Tuesday night for additional precipitation
into Wednesday as the cold front slides across Western Washington.
Additional lowland rain expected during this period, as well as
breezy east winds through the Cascade gaps and light mountain
snow. Temperatures Monday through Wednesday will be tad warmer
than normal in the upper 40s to low 50s.

.LONG TERM /THURSDAY THROUGH SUNDAY/...The pattern Thursday into
Saturday will feature ridging across the interior Rockies and
troughing offshore. This will allow for additional precipitation
across western Washington as weakening fronts move across the
area. Periods of lowland rain, mountain snow, and breezy east
winds are expected late week. An upper low will then move eastward
into California allowing for showers lingering into Sunday, with
perhaps some drier weather early next week. Temperatures slightly
above normal across Western Washington during this period.

Davis/JD

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.AVIATION...South-southwest flow aloft this evening with deep
troughing over the northeastern Pacific. At the surface, winds
are light and somewhat variable this evening, though primarily
southeasterly. A mix of VFR and MVFR CIGs this evening, with some
patchy stratus around the Southwest Interior near HQM, OLM, and
PWT. A more substantial frontal system will bring rain and MVFR
to IFR ceilings tomorrow with gradual progression downward from
west to east. Offshore winds should remain light tonight before
beginning to pick up tomorrow.

KSEA...VFR conditions with light and variable winds, but primarily
southeasterly. CIGs should remain VFR through tonight. MVFR
conditions look possible tomorrow after around 18Z with more
substantial rain as the next frontal system moves towards the
area also bringing stronger southeasterly winds with gusts up to
20 kt possible after 18-20Z.

Davis/LH

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.MARINE...Added an SCA for Puget Sound and the Hood Canal this
evening with latest hi-res guidance bringing southeasterly wind
gusts above 20 kt for much of the zones into tomorrow afternoon.

Low-level offshore flow is present as a 1030mb surface high
resides east of the Cascades and low pressure is over the NE
Pacific. SCA remains over the coastal waters where winds are
increasing ahead of the next front. SCA winds will continue to
spread inland today along with the aforementioned frontal boundary
with SCA in place for most inland water zones. Activity will
continue into Monday as wind speeds will increase over all waters.
Inherited gale watches for the nearshore coastal waters and the
Eastern Strait have been upgraded to warnings. Additionally, the
Central Strait and Northern Inland Waters have been included into
this batch of Gale Warnings. The Western Strait and Admiralty
Inlet will see speeds remain in SCA criteria, although there may
be a brief lull in winds for the Western Strait at times tonight.
The SCA for rough bar at Grays Harbor has been extended. Lastly,
as alluded to in the previous discussion, models remain persistent
that while winds over the outer coastal waters will get close to
or slightly exceed 40 kts, they do not look to encroach on Storm
criteria /exceeding 48 kts/. As such, the Storm watch there has
been transitioned into a Gale Warning.

Combined seas 12 to 14 ft, rising to 15 to 18 ft in the nearshore
coastal waters Monday night while the outer waters may get as high
as 20 to 22 ft.

Davis/18

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.HYDROLOGY...A series of frontal systems will move across the
region this week, with the focus of heaviest precipitation
expected to be over the Olympic Peninsula. With heavier rain and
relatively high snow levels, expect increased potential for sharp
rises on rivers- especially those draining from the Olympics. The
Skokomish River at Potlatch may reach flood stage as early as
Monday night. Fluctuations in forecast QPF will impact the degree
to which the Skokomish River is expected to flood, with some
uncertainty in the current forecast. Elsewhere, rivers will rise
but flooding is not expected.

JD

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 7 AM Monday to 4 AM PST Tuesday for Admiralty
     Inlet Area-Eastern Strait of Juan de Fuca-North Coast-San
     Juan County.

     Wind Advisory from 10 AM Monday to 4 AM PST Tuesday for Western
     Skagit County-Western Whatcom County.

     Winter Weather Advisory from 4 AM Monday to 10 AM PST Tuesday
     for West Slopes North Central Cascades and Passes-West
     Slopes South Central Cascades and Passes.

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

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

     Gale Warning from 4 AM Monday to 1 AM PST Tuesday for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning from 4 AM Monday to 4 AM PST Tuesday 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-Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 10 AM Monday to 10 AM PST Tuesday for
     Puget Sound and Hood Canal.

     Small Craft Advisory until 1 AM PST Monday 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 1 AM Monday to 4 AM PST Tuesday 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.

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