197
FXUS66 KSEW 272127
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
227 PM PDT Sat Apr 27 2024

.SYNOPSIS...The active weather pattern will continue into early next
week as a series of fronts pass through the region. Snow is expected
in the passes Sunday night into Monday. A trend toward temperatures
closer to normal and somewhat drier conditions is expected during
the later half of the coming week.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Light precip continues to
spread across the area this afternoon ahead of an occluded front
that will dissipates as it moves onshore this evening. A few showers
will linger over Western Washington overnight behind the front. An
upper trough west of Haida Gwaii will dig southward into the region
later Sunday into Monday for cool, showery conditions. The cooler
temperatures aloft will destabilize the atmosphere enough for a
slight chance of thunder as well as lower snow levels to most of the
passes by Sunday night into Monday. Relatively warm ground
temperatures may limit accumulations at Snoqualmie Pass. Nonetheless,
higher Steven Pass may accumulate somewhere in the range of 5 to
7 inches over a 12 hour period (06Z-18Z Monday). Another shortwave
arrives Monday night into Tuesday. The focus with the precip with
that system may be a little further south...perhaps mainly the
southern half of the CWA.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Deterministic model runs
have shown little to no run-to-run consistency for the long term
forecast over the past couple of days. And this meshes well with the
high degree of uncertainty expressed by the NBM during that time
period. There`s increasing confidence that we`ll see a short break
in the weather on Wednesday, but the forecast picture becomes
increasingly murky Thursday through Saturday. Despite the fact that
deterministic runs of the GFS/Euro have flipped from earlier
solutions, some of the ensemble means (the Euro in particular)
maintain some positive height anomalies late next week. Current
forecasts for late next week look awfully close to climatological
norms...and that`s probably not a bad approximation at this time.

27

&&

.AVIATION...West-southwest flow aloft through the TAF period as
upper level troughing moves across the Pacific Northwest. A mix of
IFR, MVFR, and VFR CIGs this afternoon with rain and showers pushing
across the area. Any lingering VFR ceilings should lower tonight to
mostly MVFR. S-SW surface winds for area terminals (W for KCLM)
between 8-12 kt. Gusts up to 20-25 kt are possible this evening as a
front passes.

KSEA...VFR CIGs currently with rain showers along with a 30% chance
of MVFR through the remainder of the afternoon. Rainfall may be
steadier at times this evening as a front tracks over the terminal.
A gradual trend back to MVFR through the night is expected.
Southwesterly winds through the TAF period, with gusts to 20 kt
possible through this evening. VFR should rebound into Sunday.

McMillian

&&

.MARINE...A frontal system is currently moving into area waters. SCA
are posted for most marine zones through this evening as the
aforementioned front passes. Most should be allowed to expire
tonight but a westerly surge through the strait will keep the
advisory going for the central and east strait through early Sunday
morning. Marginal wind gusts to SCA thresholds possible Sunday
afternoon (35% chance) over the offshore waters with another round
of Small Craft Advisories likely through the Strait with another
afternoon push and possibly through the beginning of next week.

Seas 6 to 8 feet tonight and through much of the day Sunday. Seas
look to increase to 8 to 10 feet Sunday night into Monday. Seas then
remain below 10 feet Tuesday onward.

McMillian

&&

.HYDROLOGY...No river flooding is expected over the next seven
days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory from 11 PM Sunday to 11 AM PDT Monday
     for West Slopes North Cascades and Passes-West Slopes North
     Central Cascades and Passes-West Slopes South Central
     Cascades and Passes.

PZ...Small Craft Advisory from 8 PM this evening to 5 AM PDT Sunday
     for Central U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 5 AM PDT Sunday for East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 11 PM PDT this evening for Admiralty
     Inlet-Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory until 8 PM PDT this evening 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.

&&

$$