779
FXUS66 KSEW 230245
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
745 PM PDT Thu May 22 2025

.SYNOPSIS...Warmer and drier conditions across Western Washington
through the end of the week as high pressure builds over the region.
An approaching front may bring some mountain showers Monday and a
slight pause on warmer lowland temperatures, but dry and warm
conditions return early next week. Another disturbance approaches
around the middle of next week, but confidence in a pattern change
is low.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...A quiet evening over
W WA with no echoes present on radar and a mix of high and mid-level
clouds on satellite. Current obs show most locations still seeing
temps in the 60s although starting to see some spots cool off into
the mid to upper 50s, especially near water. Will see at least some
of the cloud cover ease a bit more, as mid clouds from instability
due to daytime heating will flatten, then scatter out. Spots that do
clear out, especially in the SW interior, could see overnight lows
dip into the upper 30s...while remaining spots should see enough
scattered clouds to keep lows slightly warmer in the 40s.

Inherited forecast covers this well and remains on track, as such,
no need for any evening update. For additional forecast details,
please refer to the Previous Discussion section below.

18

From Previous Discussion...Temperatures have warmed into the 60s for
much of the interior already this afternoon under mostly sunny skies
across much of the region, while some banks of clouds remain along
the mountains and extending into the lowlands of Lewis County. With
zonal flow in place over the region and light low-level flow, not
seeing much change over the next 24 hours or so. Expect another day
with primarily sunny skies and temperatures again near normal on
Friday. It`s worth noting that some spots with clear skies and light
wind could drop into the upper 30s in the typically colder spots,
while most of the area will bottom out in the 40s.
Looking ahead to Saturday, the heights will rise over the region
in response to the upper low dropping from the Gulf of Alaska.
This will bring warming across the region with afternoon
temperatures into the 70s for the interior.

.LONG TERM /SUNDAY THROUGH THURSDAY/...The upper ridge remains
in place this weekend, with Sunday likely the warmest day for
most Expect temperatures to reach well into the 70s and a few of
the warmest spots could even approach 80. With the offshore
trough in place and the ridge axis shifting east, there is some
potential for increasing southwesterly flow aloft to perhaps
bring a focus for some convection near the Cascades late Sunday
or early Monday. While the chances for thunderstorms remains
somewhat low (around 10%) at this time, those with outdoor plans
in the Cascades over the holiday weekend will want to maintain
aware of this potential. With the passing disturbance on Monday,
expect temperatures to run a few degrees cooler with increasing
clouds and a cooler air mass.

Another round of higher heights on Tuesday/Wednesday with
another ridge building over the area will bring another round of
temperatures will into the 70s for the interior as southerly
flow aloft settles over the region. Confidence in the details of
the forecast break down around midweek with ensemble guidance
split between maintaining the high pressure over the region and
warmer temperatures to persist and allowing the next front to
push through the Pacific Northwest and bring slightly cooler,
cloudier conditions with a return of rain chances.

&&

.AVIATION...West flow aloft as the upper-level pattern trends
more zonal. VFR continues this evening across all terminals with
scattered to broken ceilings. There is a 30-50% chance of cigs below
3,000 ft exists for KHQM, KPWT, and KPAE overnight into Friday
morning. Friday will be VFR region-wide later in the morning into
the afternoon/evening. Mix of southwest to northwest winds at 5 to
10 kt continue this evening, which will become light and variable
tonight, and more west-northwest regionwide Friday.

KSEA...VFR conditions expected through the TAF period. Winds WSW 5-
10 kt this afternoon before becoming lighter and variable later this
evening/tonight Cloud coverage will vary throughout the period but
again, cigs aren`t expected to be less than 5,000 ft.

McMillian/HPR

&&

.MARINE...High pressure will maintain into the weekend. A weak
disturbance is still on track to dissipate before making it to the
coastal waters on Friday. As a result, impacts are unlikely. What
we`ll have to watch is diurnal westerlies through the Strait of Juan
de Fuca. For tonight, HREF guidance has a 60-80% chance of SCA gusts
(21-25 kt) occuring over the central/east strait. This is a marginal
situation as gusts appear to be infrequent but we`ll continue to
monitor the threat this afternoon-early evening.

The next front is currently forecast to arrive on Monday, with high
pressure remaining stubborn over the coastal waters shortly
afterwards. High pressure may trend into Wednesday as well but of
lesser strength.

Seas 3-5 ft tonight into Friday. A slight uptick in seas is expected
again Saturday night into Sunday, with seas building towards 5-7 ft.
Seas then look to persist within this range through the early part
of next week.

McMillian

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.

&&

$$