063
FXUS66 KSEW 180321
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
821 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.

&&

.UPDATE...Evening remains dry and a mix of clouds and sun
continue through the evening. Updated aviation section below,
otherwise forecast remains on track.

HPR

&&

.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

&&

.AVIATION...West to northwest flow continues into Saturday with an
upper trough over the Pacific Northwest. Generally VFR mid to high
clouds this evening with onshore flow at the surface. Another trough
will move through on Saturday for lowering cigs into Saturday
morning. Generally MVFR Saturday morning with some areas remaining
low end VFR. In addition, light rain increases Saturday morning and
continues into the afternoon, especially over central Puget Sound
with convergence activity. MVFR cigs will slowly improve to VFR,
generally 3000-5000 ft Saturday afternoon before some SCT/BKN later
Saturday. Rain showers dissipate later Saturday. Localized IFR
cannot be ruled out either Saturday morning, but expected to be
isolated. Light S/SW west tonight with increasing onshore flow on
Saturday.

KSEA...VFR conditions continue through early tonight. Cigs will
begin to lower tonight into Saturday morning with low level moisture
and a system moving towards the area. MVFR cigs expected to develop
late tonight into Saturday morning, with slow improvement to VFR
Saturday afternoon. Rain potential increases Saturday afternoon
before dissipating in the evening. Southerly winds continue into
Saturday morning before shifting north Saturday afternoon. Although
north winds are expected to remain generally below 7kt on Saturday,
there may be brief periods of N winds 7-10 kts. JD

&&

.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.

&&

$$