341
FXUS66 KSEW 172159
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
259 PM PDT Fri May 17 2024

.SYNOPSIS...Upper level troughing will be the main feature over
western Washington this weekend, keeping showery and cooler
conditions around. A weak ridge looks to briefly build in the area
for the start of next week, before troughing returns for more
cool and showery conditions.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...Upper-level trough is east
of the Cascades as its axis is over the Inland Northwest. Upstream,
a transient ridge is taking aim at western Washington as it`s
currently overhead Vancouver Island. As a result, we`ll see
mostly dry conditions across the area this evening. Can`t rule out
spotty light showers for higher elevations tonight. Otherwise,
benign weather is in the forecast. Overnight lows are to fall into
the low to mid 40s.

Widespread precipitation looks to return on Saturday. The next
upper-low is slated to arrive with rain showers and below normal
high temperatures in the mid 50s to near 60 F. A few showers are
to remain on Sunday, mostly over the mountains before conditions
dry out overnight as upper-level ridging builds overhead. This
will set up a dry day on Monday as deterministic models indicates
the aforementioned ridge axis nosing into BC and far western
Alberta. We`ll also see the warmest temperatures of the upcoming
week on Monday with highs in the mid 60s to near 70 F, around
average for mid-late May. But, rain and cooler temperatures will
soon return as the week continues. Overnight lows are to remain in
the 40s through the short term forecast.

.LONG TERM /TUESDAY THROUGH FRIDAY/...As hinted, we`ll be back to
regularly scheduled programming starting on Tuesday. Active weather
looks to resume as another upper-low out of BC dives south into
the region followed by an additional shortwave sliding through on
Wednesday. Showery and cool weather will continue into the long
term period with temperatures slightly below normal.

McMillian

&&

.Northwesterly flow will persist aloft today as an
upper level trough over WA/ID continues to push east and a ridge
of high pressure remains situated over the NE Pacific. Flow aloft
will become more westerly into Saturday as another trough drops
down into WA from BC. Post- frontal onshore flow will continue
tonight into Saturday. Radar this afternoon shows some light
showers in the north and central Cascades, but shows showers
gradually diminishing. Conditions widespread VFR this afternoon
and expect conditions to remain so through tonight. With the low
level air mass remaining moist, and with onshore flow continuing,
expect to see another round of MVFR cigs develop overnight into
Saturday morning. An approaching shortwave will bring another
round of showers to the area on Saturday and could result in
localized MVFR to IFR conditions at times across area terminals.

KSEA...VFR conditions to persist through tonight. With low level
moisture, could see another round of MVFR conditions develop
early Saturday. Winds generally S/SW persisting at 8 to 12 kt,
with a few gusts to 20 kt. Winds look to ease towards 5 to 10 kt
overnight and then shift to the N, but persist at 7 kt or less
Saturday afternoon into evening. Showers will possible at times on
Saturday. 14

&&

.MARINE...High pressure over the NE Pacific will interact with
lower pressure inland and will maintain onshore flow across the
region through the weekend. Strongest winds will likely be along
the Strait of Juan de Fuca with Small Craft Advisory winds looking
to persist through late tonight. The next frontal system then
looks to move across the area waters on Tuesday.

Seas hovering at 7-9 ft across the coastal waters this afternoon.
Expect seas to continue to subside towards 5-7 ft over the weekend
and to persist into early next week. 14


&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT Saturday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

&&

$$