249
FXUS66 KSEW 041004
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
304 AM PDT Fri Apr 4 2025

.SYNOPSIS...High pressure will build into the region through the
remainder of the week, allowing conditions to dry out and warm up.
Wet and cooler conditions are on track to return towards the end
of the weekend and continue through mid-week as troughing settles
into the Pacific Northwest.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...With dry northerly flow
aloft, temperatures will continue to dip early this morning into
the 30s across the lowlands. Patchy fog alongside areas of frost
are favored to develop south of the Puget Sound, including Olympia
southward across the Chehalis River Valley. A Frost Advisory
remains in effect for these areas through the mid morning. High
pressure will continue to amplify inland throughout the day today,
allowing for mostly sunny skies by the afternoon and temperatures
peaking in the mid 60s across the lowlands.

High pressure will continue to amplify and shift inland through
Saturday, maintaining mild conditions across western Washington.
However, incoming cloud cover from an approaching storm system
will limit temperatures to the upper 60s to low 70s for most
areas Saturday.

The next chance for widespread precipitation increases late
Saturday night as a front moves inland across the Pacific
Northwest. Precipitation will reach the coast by early Sunday
morning, filling in eastward throughout the day. Southwest flow
aloft will maintain mild temperatures in the 60s across the
lowlands with snow levels between 6000-7000 feet on Sunday.

.LONG TERM /MONDAY THROUGH THURSDAY/...A cold front will push
inland late Sunday into Monday, maintaining widespread showers as
temperatures cool back into the 50s and snow levels lower to
2500-3000 feet. Moist westerly flow is favored to continue
through the first half of next week, with periods of breezy winds,
persistent rainfall over the lowlands, and periods of
accumulating mountain snow.

Ensembles show ridging rebounding over the western US towards the
end of next week, but a large amount of uncertainty remains over
the northwestern extent of the ridge. However, offshore troughing
maintains a slight chance of precipitation throughout the extended
forecast period.

15

&&

.AVIATION...North winds aloft as an upper level ridge begins to move
eastward towards western Washington. VFR conditions remain across
the region early this morning, with winds generally out of the north
to northeast. Some fog and patchy IFR cigs are possible later this
morning, generally after 15Z in places like OLM, PWT and HQM, but
isn`t expected to last much longer than 18Z. However, temperatures
in these locations may be cold enough for some frost. Elsewhere,
expect northerly winds and VFR cigs throughout the TAF period.

KSEA...VFR conditions remain at the terminal early this morning and
likely through the rest of the TAF period , with northeasterly winds
between 7 and 10 kts. Wind speeds will ease to around 5 to 7 kts
after 12Z, but remain northerly. After 06Z tonight, winds may become
southeasterly.

21

&&

.MARINE...Broad high pressure over the northeast Pacific will remain
in place through Sunday, continuing the period of light winds and
seas. The next frontal system will move through the waters on
Sunday, bringing a quick round of breezy winds which may require
headlines. Additional systems look to traverse the area waters early
next week, keeping breezy conditions in the forecast.

Combined seas 3 to 5 feet through the rest of the week and into the
weekend. Seas will start to gradually build upwards Saturday night
into Sunday, reaching 10 to 13 feet Sunday and remaining in the 8 to
12 ft range through early next week.

62/21

&&

.HYDROLOGY...No river flooding is expected over the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Frost Advisory until 9 AM PDT this morning for Lowlands of Lewis
     and Southern Thurston Counties-Middle Chehalis River Valley-
     Olympia and Southern Puget Sound.

PZ...None.
&&

$$