255
FXUS66 KSEW 041029
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
329 AM PDT Sat May 4 2024

.SYNOPSIS...A return to cool and unsettled conditions will
continue across the Pacific Northwest this weekend, with little
change through early next week. A shift in the pattern is then
expected for the second half of next week as high pressure aloft
likely develops over the region. This will bring a return of drier
and much warmer conditions to the region.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...Latest NWS radar imagery
reveals the steady precipitation has largely remained draped along
and south of a roughly Port Angeles to Mount Rainier line early
this morning. With the boundary making little significant
progress, still expect the progression of any rain north of
Seattle to be rather minimal through the morning today. Some light
rain likely expands inland and a little more north, but the focus
for the consistent precipitation will remain across the
southwestern portions of the local area. In fact areas of Whatcom
County near the border will likely remain mostly dry and also a
bit on the warmer side. The upper level trough slides east of the
region by early Sunday but remains close enough to continue to
spread some showers across the local area. More significantly, the
next cold upper trough induces stronger onshore flow as it
approaches, which will increase the rain coverage across the
region. With stronger orographic support, expect heavier rainfall
up in the mountains (and snow in the higher Cascades above 4000
ft or so) but some shadowing to keep rainfall totals in the
Seattle metro area notably lower. We stay locked in the active
pattern with the upper trough crossing the region into Monday. As
lapse rates steepen, will have the potential for some isolated
thunderstorms and stronger onshore flow will likely bring a
developing Puget Sound Convergence Zone.

.LONG TERM /TUESDAY THROUGH FRIDAY/...The start of the long term
period likely remains unsettled and showery with the lingering
upper trough still over the region. Strong support in the ensemble
guidance for a pattern shift around midweek though, with high
confidence in an upper ridge taking shape over or near the region.
While still some subtle variations among the various clusters of
solutions, the general trend suggests this warmer and drier
weather will be with us for the second half of the week. Have
maintained temperatures in line with the NBM, with likely
temperatures in the mid to upper 70s across much of the lowlands
late in the week.

&&

.AVIATION...Frontal system moving over the southern portion of
the area today. Upper level low associated with the front moving
inland near the Oregon California border this evening. The low
will slowly move east tonight and Sunday. Southeasterly flow aloft
becoming easterly tonight and westerly Sunday. In the lower levels
increasing onshore flow later this afternoon through tonight with
onshore flow continuing Sunday.

Wide variety of ceilings across the area today. MVFR ceilings from
about a Hoquiam to Tacoma line southward. VFR ceilings to the
north. MVFR ceilings expanding northward later this afternoon and
evening to around Everett. MVFR ceilings from Everett south
continuing through Sunday morning with VFR ceilings over the
Northwest Interior.

KSEA...Ceilings aoa 5000 feet into early afternoon. Ceilings
lowering to 3500-4500 feet after 21z and to 2000-3000 feet after
00z. Variable wind 5 knots or less becoming southwest 4 to 8 knots
after 00z. Felton

&&

.MARINE...A frontal system will move through the southern
portion of the waters today. Another system will move across the
waters Sunday night into Monday morning. High pressure will
build back over the area Monday night and Tuesday with the ridge
remaining in place Wednesday.

Small craft advisory westerlies in the Central and Eastern Strait
of Juan de Fuca tonight with the small craft winds continuing in
the Central Strait into Sunday morning. Small craft advisory
westerlies likely in the Central and Eastern Strait both Sunday
and Monday night with small craft advisory northwesterly winds in
Admiralty Inlet Monday night.

Seas building close to 10 feet Monday night into Tuesday. Felton

&&

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

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 6 PM this evening to 8 AM PDT Sunday
     for Central U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 6 PM this evening to 5 AM PDT Sunday
     for East Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$