Boston Harbor, Washington Weather Forecast Discussion

620
FXUS66 KSEW 271537
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
837 AM PDT Sat Sep 27 2025
.SYNOPSIS...A frontal system will clip the northern portions of
Western Washington today, bringing light rain. Another frontal
system will move through the region Sunday through Monday bringing
widespread precipitation. An active weather pattern is favored
through late next week as additional frontal systems are expected to
impact the region.
&&
.SHORT TERM /TODAY THROUGH MONDAY/...No major updates have been
made this morning. See below for previous forecast discussion and
updated aviation sections.
Light shower activity is expected to continue throughout the day
today across the northern portions of Western Washington as a
frontal system clips the northern part of the region. Rainfall
amounts are expected to remain light, generally 0.10 or less.
However, the north coast may see up to 0.30 inches. Widespread
rain is expected Sunday and Monday a frontal system pushes through
Western Washington. Thunderstorms remain possible Sunday evening,
with a 10%-20% chance along the coast. Another chance (10%-15%)
for thunderstorms is possible along the Cascades and foothills
Sunday afternoon. Rainfall amounts with this frontal system from
Sunday to Monday will be around 0.25-1.00 inches for the interior
and 1.00-2.00 inches for the coast.
.LONG TERM /TUESDAY THROUGH FRIDAY/...Ensemble guidance continues to
generally favor unsettled conditions to continue into next week, as
additional frontal systems are expected to impact the region.
Guidance is in good agreement that a low pressure system will drop
down from the Gulf of Alaska Tuesday into Wednesday and remain
offshore. However, there is some uncertainty regarding the forecast
Thursday and Friday. As for Thursday, differences become apparent
between the deterministic models. The GFS model has the center of
the low pressure system moving southward into Oregon/California,
which favors a slightly drier solution for Western Washington. The
European model has the center of the low pressure system moving
inland into Western Washington, which favors a wetter solution. At
this time, the majority of ensemble members (85%) seem to favor a
solution similar to the European model. Uncertainty continues into
Friday, with ensemble members being almost evenly split between weak
ridging and troughing over Western Washington. Moreover, guidance
continues to show a small chance of thunder next week, with
probabilities between 10%-20%.
29
&&
.AVIATION...A weak cold front slowing inland this morning continues
to produce light showers across north interior terminals. Radar was
tracking activity moving northeast from the Kitsap area up to Skagit
County, and a few areas of drizzle in the south interior up through
King County moving east. Cigs are VFR with mid to high clouds
everywhere except the coast (MVFR continues along there and models
even suggest lower cigs down to LIFR by this afternoon as the front
moves in). While VFR conditions will continue in the interior
tonight, chances of IFR/LIFR increase inland Sunday morning (40-
60%), with onset expected 10-14Z, with lifting/scattering to VFR
taking place 18-21Z. Flow aloft will increase and shift from west to
southwest. Light WSW winds 3-6 kt will shift north 5-10 kt after 00Z
and become light and variable tonight/Sunday morning shifting back
to the south.
KSEA...VFR conditions with mid and high clouds through the morning
with a few light rain showers possible early. Ceilings will lift and
scatter out by late afternoon, then build back in by 4-6Z, with a 40-
50% chance of ceilings at or below 1kft by 14z. Light SE winds
tonight may become VRB between 12-18z then W/NW during the afternoon
into the evening 5-10 kt, then back to light and VRB
overnight/Sunday morning before picking up out of the S 3-6 kt.
Cook/HPR
&&
.MARINE...An approaching frontal system will bring lower
ceilings/visibilities and showers over the coastal waters during the
afternoon with elevated seas, 8-11 ft through the weekend. An
additional frontal system Sunday into Monday will maintain elevated
seas at or around 7-9 ft Sunday through Monday. Ensembles now
showing anywhere between 80 to 100% odds of small craft advisory
winds and gusts over the coastal waters, and the interior waters
(particularly East Strait of Juan de Fuca and Northern Inland
Waters) Sunday into Monday. A stronger system digging southward from
Alaska Tuesday and Wednesday will likely increase seas up to 10-15
ft Tuesday into Thursday, with increased odds of strengthened south
winds in the coastal waters, Strait of Juan de Fuca and interior
waters.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for Coastal
     Waters From Cape Flattery To James Island Out 10 Nm.
Small Craft Advisory until 11 PM PDT this evening 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.
&&
$$

NWS SEW Office Area Forecast Discussion