391
FXUS66 KSEW 140937
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
237 AM PDT Tue May 14 2024

.SYNOPSIS...A ridge of high pressure will provide dry and warmer
conditions for the region through Wednesday. An upper trough dipping
southward from British Columbia will produce clouds and cooler
temperatures Thursday through Saturday along with a chance for
showers across mainly northern portions of the area. Below normal
temperatures and somewhat unsettled conditions could persist into
the early part of next week.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...An upper ridge centered
well to our southwest will build into the area today and Wednesday.
This will allow for dry conditions and a modest warming trend. Low
level onshore flow will keep temperatures in check with 60s for
coastal areas and mid 60s to mid 70s for the interior lowlands. The
upper ridge will flatten on Thursday in response to an upper level
trough moving onshore over British Columbia. This will act to
increase the onshore flow and the end result will be increasing
cloud cover and cooler temperatures. Onshore flow becomes relatively
strong Thursday afternoon into Thursday night and this will likely
initiate a convergence zone over Skagit/Snohomish counties.


.LONG TERM /FRIDAY THROUGH MONDAY/...An upper trough axis will be
over Western Washington on Friday for another mostly cloudy and cool
day. The best chance for showers will be over the mountains and
across northern portions of the lowlands. Snow levels will dip to
around 5000 feet...something to consider if you`ve got hiking plans
in the higher backcountry late this week. For the weekend and
beyond, uncertainty is the word for the day to day forecast. Cluster
plots show a considerable spread in solutions. Ensemble height
anomalies show ridging retrograding well offshore with a mean upper
trough position over the Northern Rockies heading into early next
week. While not a particularly wet scenario, this does suggest that
temperatures will be a little below average and shower chances will
linger...especially over the higher terrain.

27


&&

.AVIATION...Upper level ridging in the eastern Pacific will keep
northwesterly flow aloft over W WA at least into Wednesday. Surface
flow this early morning generally light and variable with a few
exceptions reporting northerly winds 5-10 kts. Majority of TAF sites
should see similar low level winds develop by this afternoon.

Widespread VFR conditions this early  morning with only UIL
reporting MVFR. Inherited forecast suggests MVFR conditions after
12Z for many sites although current models backing away from those
solutions. Will likely gear 12Z TAF updates more toward keeping VFR
conditions in place, although with some SCT lower clouds possible.
Locations more prone to lower cigs, such as HQM, OLM and PWT still
seem on track for MVFR to emerge in the early morning before lifting
by around 18Z. VFR conditions expected over the entire area this
afternoon and evening.

KSEA...VFR conditions expected to persist throughout the TAF period,
although some SCT020 possible after 12Z. Fair conditions expected
after 18Z, with only high clouds to consider. Northerly winds 6-10
kts will persist through about 15Z before turning light and
variable. Northerly winds 5-10 kts return by 20Z and persist into
early Wednesday morning.

18

&&

.MARINE...High pressure will build off the coast throughout this
week. North to northwesterly surface winds starting out over the
Pacific waters then pushing inland will give rise to SCA concerns
throughout the day. Headlines are staggered from west to east and
limited to the coastal waters and Strait at this time, although
consideration for Strait-adjacent waters may be needed depending on
future model solutions. At the very least, headlines with early
morning forecast package will cover the next 12-18 hours, allowing
for better near-term analysis. Another push down the Strait is
possible for Wednesday into Thursday while the coast may see speeds
ramp up for late Thursday and all of Friday.

Seas will hold around 4 to 6 ft through Friday before increasing 8
to 12 ft from Friday into the weekend.

18

&&

.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 11 PM PDT this
     evening for West Entrance U.S. Waters Strait Of Juan De
     Fuca.

     Small Craft Advisory from 2 PM this afternoon to 5 AM PDT
     Wednesday for Central U.S. Waters Strait Of Juan De Fuca-
     Coastal Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville Out 10
     Nm-Coastal Waters From Point Grenville To Cape Shoalwater
     Out 10 Nm.

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

     Small Craft Advisory until 5 AM PDT Wednesday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.

&&

$$