657
FXUS66 KSEW 050354
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
854 PM PDT Sat May 4 2024

.SYNOPSIS...Cool and unsettled weather will continue over western
Washington into early next week. A pattern shift can be expected
by midweek as upper level ridging builds over our region, bringing
drier and a much warmer conditions to our area.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Cutoff upper low and
attendant surface low continue to slowly move across Oregon and
parts of the Great Basin this evening. Precipitation coverage has
dwindled to some extent on radar, though light drizzle, mist, and
otherwise damp conditions persist across most of western
Washington. Much of the remaining rain into tonight will be
focused along the coast, the Olympic Peninsula, and Olympia
southward as thats where the boundary is focused. Low temperatures
tonight won`t drop a whole lot with mid to low 40s across the
region.

The broad area of low pressure associated with an upper level
trough will continue to move eastward inland on Sunday, but will
still remain close enough to continue showers for western
Washington. With another trough right behind it, onshore flow will
be strong Sunday providing more wetter conditions, especially for
interior locations. Along with rain showers throughout the
interior, some snow can be expected in the higher Cascades..
generally around 4000 to 5000 feet, but will be rather light.

As the upper level trough crosses the region into Monday, cooler
air aloft will help produce some instability along with steep
lapse rates, which could help the development of some isolated
thunderstorms over the interior into Monday afternoon. Strong
onshore flow will continue as well, also prompting the development
of a potential Puget Sound Convergence zone into Monday evening.

Unsettled showery conditions look to continue through Tuesday and
Wednesday as the upper level trough lingers over the region.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...There is strong support
from ensemble guidance that a pattern shift is upon western
Washington, with an upper level ridge building over the region
starting on Wednesday. Although there are some small variations in
timing and placement of the upper level ridge, there is a general
agreement that much warmer and drier conditions will take place
throughout much of the long term, with NBM high temperatures in
the lowlands around mid to upper 70s into Friday and Saturday.

Davis/Mazurkiewicz

&&

.AVIATION...An upper low will move into the Oregon-California border
this evening with southeasterly flow aloft transitioning westerly on
Sunday. Generally VFR north of the Seattle terminals this evening
with MVFR/IFR across the coast and southern Puget Sound. CIGs will
continue to slowly lower through the night to where most all
terminals will be MVFR/IFR by Sunday morning. Light rain will
continue at times into early tonight, with another round of lighter
rain on Sunday. Some improvement to CIGs possible by Sunday
afternoon, especially north of Seattle, but generally MVFR to low-
end VFR expected through the TAF period. Southerly winds through the
TAF period, increasing overnight to 10 to 15 kt with gusts to 25 kt
possible in the afternoon tomorrow.

KSEA...MVFR ceilings this evening. CIGs will remain low-end MVFR
with potentially periods of IFR tonight into Sunday morning. CIGs
generally remain MVFR Sunday afternoon with light rain at times.
Southerly winds, increasing overnight, becoming gusty by tomorrow
afternoon and evening.

JD/LH

&&

.MARINE...A frontal system will move through the southern portions
of the waters into this evening. Another weather system will move
across the waters Sunday night into Monday. Northwesterly winds this
evening will transition more west to southwesterly tonight into
Sunday. A westerly push through the Central and Eastern Strait of
Juan de Fuca tonight will result in brief Small Craft Advisory level
wind gusts, for which a Small Craft Advisory is in effect through
tomorrow afternoon. West winds then increase through the Strait of
Juan de Fuca again Sunday afternoon into early Monday for another
round of SCA winds. Winds may also reach SCA for adjacent areas,
including Admiralty Inlet and Northern Inland Waters, and south of
the San Juan Islands during this period. In addition, winds will
increase Sunday afternoon into Monday morning for Puget Sound with
an increased likelihood of SCA wind gusts during this period.

Additional westerly pushes through the Strait of Juan de Fuca are
likely Monday and Tuesday evening. Winds will then transition more
northerly Wednesday into late week as high pressure builds into the
area.

Seas of 5 to 8 feet will continue into Monday before building to 9
to 12 feet Monday night through Tuesday.

JD

&&

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

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 2 PM 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.

&&

$$