167
FXUS66 KSEW 241027
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
327 AM PDT Tue Jun 24 2025

.SYNOPSIS...Zonal flow aloft over Western Washington today. A
series of weak systems will move by mainly to the north Wednesday
through Friday. An upper level ridge will build over the area
during the weekend with the ridge remaining in place for the first
part of next week.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...Satellite imagery shows
stratus right along the coastline with just a few high clouds over
the remainder of the area. Temperatures at 3 am/10z were in the
upper 40s and 50s.

Zonal flow aloft over Western Washington today with light flow in
the lower levels. Stratus along the coast will dissipate later
this morning. High clouds out ahead of a weak shortwave will
spread over the area in the afternoon. Highs a touch warmer today
versus Monday for the interior with 70s and lower 80s. Highs along
the coast remaining in the mid 60s.

The first in a series of weak shortwaves will move by to the
north late tonight into Wednesday. Increasing low level onshore
flow overnight will lead to mostly cloudy to cloudy skies by
morning. Slight chance of showers Wednesday for most of the area
with higher pops near the Canadian border. Highs will be much
cooler with most places in the 60s. The increasing clouds
overnight will keep lows in the 50s.

Weak upper level trough over Western Washington Wednesday night
into Thursday with another shortwave moving by to the north
Thursday. This feature a little stronger than the one for
Wednesday with higher pops over the area but still in the chance
category for most of the region. Like Wednesday highest pops
Thursday near the Canadian border. High temperatures continuing to
cool into the lower to mid 60s. Lows in the upper 40s to mid 50s.

.LONG TERM /FRIDAY THROUGH MONDAY/...Extended models in good
agreement with yet another weak feature moving by to the north
Friday keeping a chance of showers in the forecast and highs in
the 60s. This shortwave will be the last in the series.

All these shortwaves will give the area very little measurable
rainfall. The current June monthly rain total at Seattle-Tacoma
airport of 0.35 inches. If it stands through the end of the month
would be the 5th driest June on record. The current 5th driest
June is 0.43 inches in 1970, 6th driest 0.46 in 1979.

Upper level ridge beginning to build Saturday with 500 mb heights
around 580 dms by 00z Sunday. Low level onshore flow weakening and
becoming more northwesterly. Warming trend starting Saturday with
highs in the mid 60s to mid 70s.

Upper level ridge continuing to build Sunday with 500 mb heights
in the mid 580 dms by 00z Monday. Northwesterly onshore gradients
continuing through the end of the weekend. Highs continuing to
warm with 70s and lower 80s for Sunday. The exception to this will
be along the coast where afternoon northwesterlies off the cool
ocean will keep highs in the upper 60s.

Little change in the pattern Monday. Upper level ridge starting to
drift east but temperatures aloft remain warm over Western
Washington, model 850 mb temperatures in the plus 17c to plus 20C
range. Low level flow never turns offshore which will put a cap on
the highs. Over the interior temperatures continue to warm with
highs in the mid 70s to mid 80s. Afternoon seabreezes along the
coast will keep highs near 70. Felton

&&

.AVIATION...Upper-level flow southwesterly throughout the period.
Expect VFR area-wide today but shallow cigs look to start the day at
KHQM. NBM suggests a 70-75% chance of cigs below 1,000 ft between 12-
16z but should burn off shortly after. VFR into the evening but
marine stratus is slated to develop overnight with MVFR to IFR cigs
becoming widespread by 12z Wednesday morning. Light winds this
morning, increasing into the afternoon between 4 to 8 knots with low-
level onshore flow.

KSEA...VFR today through the evening. Light winds this morning,
becoming SW at 4 to 8 kt in the afternoon. MVFR cigs trending early
Wednesday morning but likely to lift and gradually scatter towards
the afternoon.

McMillian

&&

.MARINE...Onshore flow will continue over the next
several days, with westerly pushes expected down the Strait of Juan
de Fuca each evening. A SCA has been issued for the central/eastern
Strait of Juan de Fuca Tuesday afternoon through early Wednesday
morning. Westerly gusts appear favorable to reach criteria. A weak
frontal system will move into the waters on Wednesday followed by
high pressure building back over the waters towards the weekend.
Seas will generally persist between 3-5 ft across the coastal waters
through much of the week.


McMillian

&&


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 4 PM this afternoon to 3 AM PDT
     Wednesday for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$