600
FXUS66 KSEW 172112
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
212 PM PDT Tue Jun 17 2025

.SYNOPSIS...A weak system will bring increased cloudiness and
chances of showers to western Washington on Wednesday. More
notable chances of precipitation are expected Friday into Saturday
as an upper low moves inland over the region. Warmer and drier
conditions are expected to return by early next week.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...A deep upper level low
spinning off SE AK and B.C. will be the main weather driver over
the Pac NW through the weekend - leading to cooler and wetter
weather.

For the short term, one last dry and mild day today but we are
seeing increasing clouds over the coast with moist, SW flow. A
weak frontal system is stalled offshore but the low will drive the
front inland on Wednesday for increasing showers over the region.
Overall, the coast and mountains may see a tenth to a quarter of
an inch with just a trace or a few hundredths in the interior
lowlands. We`re in post-frontal onshore flow Wednesday
afternoon/evening with showers mostly focused over the Cascades.

On Thursday, there`s a brief break in the weather as the low
wobbles a little south down 130W. Showers will then increase on
Friday as the low starts to track inland. Temperatures will track
cooler than average with highs in the low to mid 60s. 33

.LONG TERM /SATURDAY THROUGH TUESDAY/...A deep upper low will
keep the air mass cool and showery moving into the weekend.
Saturday looks like the wettest day with wetting rain across the
board. Up in the mountains, snow levels will be down to around
5000 ft with a few inches of snow on the higher peaks. In the
lowlands, there`s around a 40-50% chance of seeing greater than
0.15" through the day. Showers will decrease in coverage Saturday
evening as low starts to weaken and shift off toward the east.
Moving forward, early next week is trending drier as the low
departs and we`re under weak ridging from the west. Temperatures
will see a gradual increase with highs back in the low 80s
(interior) by Tuesday. The coast will remain cooler and in the 60s
with NW flow. 33

&&

.AVIATION...Southwest flow aloft will continue as an upper trough
and associated weak frontal system approach Western Washington.
The front will move onshore and dissipate early Wednesday. High
and mid level clouds will increase areawide with ceilings falling
to MVFR along the coast by early evening. These conditions will
spread to the interior terminals toward 09Z-12Z Wednesday morning.
MVFR ceilings with isolated to scattered showers will continue
through the morning on Wednesday with ceilings lifting back to VFR
in the afternoon as shower activity diminishes.

KSEA...VFR will continue into this evening under increasing high and
mid level clouds. Ceilings will then deteriorate to MVFR overnight
as a weak frontal system dissipates over the area. MVFR ceilings are
expected Wednesday morning with isolated showers in the vicinity.
Ceilings are expected to lift back to VFR Wednesday afternoon.
Surface winds S/SW 6 to 9 knots increasing to 10 to 15 knots at
times midday Wednesday. 27

&&

.MARINE...A weak front associated with a broad trough centered west
of Haida Gwaii will move onshore and dissipate early Wednesday
morning. Onshore flow will increase Wednesday afternoon into
Wednesday evening as surface ridging briefly rebuilds over the
coastal waters. Another trough and front will reach the area on
Friday with little impact. Surface ridging rebuilding well offshore
over the weekend combined with a weak trough over the inner coastal
waters may lead to some gusty northwest winds over the outer coastal
waters at times. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 2 PM Wednesday to 3 AM PDT Thursday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$