546
FXUS66 KSEW 121700
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
1000 AM PDT Sun May 12 2024

.SYNOPSIS...Upper level ridge over the area moving east this
afternoon. Weak upper level trough moving through tonight with a
weak upper level disturbance following Monday. Upper level ridge
building Tuesday and remaining in place through Friday. Upper
level trough reaching the area Saturday.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...Satellite imagery shows
weak upper level ridge over the area. Some patchy low stratus has
formed along the coast, but will likely dissipate by this
afternoon. Temperatures across the area in the mid to upper 50s,
up to 60 in Seattle as of 8AM this morning.

Upper level ridge moving east today. Light surface gradients this
morning turning onshore this afternoon. Marine air moving into the
area will drop high temperatures 10 to 15 degrees versus Saturday.

Upper level ridge well to the east tonight with low level onshore
flow continuing overnight. Weak upper level trough moving across
Western Washington. Not much moisture associated with this
feature. It will enhance the marine layer over the area. Weak
convergence over Snohomish and possibly Northern King County could
produce a light shower. Lows in the upper 40s to mid 50s.

Upper level ridge building well offshore Monday. Weak shortwave
embedded in the northwesterly flow aloft moving through bringing
just some cloud cover. This plus the stratus associated with the
marine push will make for a mostly cloudy day. Cooling trend
continues with highs only in the upper 50s to mid 60s.

Upper level ridge offshore building into Western Washington Monday
night into Tuesday. Surface gradients going northwesterly Monday
night which will limit the amount of stratus Tuesday morning. With
the warming temperatures aloft high temperatures will warm back up
above normal, in the 60s and lower 70s. Lows Monday night in the
40s.

Felton/LH

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Models starting to show
more consistency in the extended period with the upper level ridge
over the area Wednesday slowly weakening through Friday. Upper
level trough dropping down from the north Saturday. Surface
gradients remain onshore keeping temperatures from getting very
warm. Warmest day with the upper level ridge the strongest
Wednesday. Highs in the mid 60s to mid 70s. Highs slowly cooling
down to the 60s by Friday. Lows in the 40s. Upper trough bringing
more cloud cover and a chance of showers to the Cascades Saturday.
Highs remaining near normal, in the 60s.

Felton

&&

.AVIATION...Westerly flow aloft will back to southwesterly
tonight as an upper ridge gives way to a weak upper trough and
associated front that will cross the region late tonight into early
Monday. Some patchy MFR stratus developed near the coast this
morning but should scatter in the next few hours. However,
increasing onshore low-level flow will bring a push of IFR to low
MVFR stratus to the coast this evening. Meanwhile, expect ceilings
to gradually lower into the MVFR range early Monday morning with
gradual lifting to VFR possible later in the day.

KSEA...VFR with increasing high level moisture expected late this
afternoon into the evening. Ceilings expected to fall to the low end
of MVFR by 12Z-15Z Monday. Surface winds increasing northerly
through the day, with speeds reaching 6-8 kt this afternoon and
evening. Confidence on wind direction becomes lower after 12z, with
the most likely scenario being a return to southerly winds. However,
if the onshore push through the Strait of Juan de Fuca is stronger,
this could create a more variable wind direction or delay this
switch.

Cullen

&&

.MARINE...Broad surface ridging offshore with lower pressure inland
will remain the general synoptic situation through much of the week
ahead leading to varying degrees of onshore flow. Meanwhile, seas
remain rather choppy with the persistent winds over the coastal
waters.

A pair of weak systems passing mainly to the north of the
area tonight and Monday will enhance the onshore flow for gales
later today in the central/east strait and small craft advisory
conditions for adjacent waters as well as the coastal waters.
Onshore gradients look to temporarily weaken midweek before
additional weak systems increase the onshore flow again later in the
week. Seas will build a bit with each passing system to 7 to 9 feet,
with periods remaining short, around 8 seconds, through the middle
of the week.  All in all, this looks very much like a typical late
spring/early summer type of pattern.

27/12

&&

.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 from 2 PM this afternoon to 4 AM PDT Monday
     for West Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 2 PM this afternoon to 4 AM PDT Monday for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 3 AM PDT Monday for Northern Inland
     Waters Including The San Juan Islands.

     Small Craft Advisory from 5 PM this afternoon to 4 AM PDT Monday
     for Admiralty Inlet.

     Small Craft Advisory until 11 PM PDT this evening for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From James Island To Point Grenville
     Out 10 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville
     To Cape Shoalwater Out 10 Nm.

&&

$$