777
FXUS66 KSEW 162229
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
329 PM PDT Wed Apr 16 2025

.SYNOPSIS...Upper level ridge building into the British Columbia
coast tonight will slide south over Western Washington by Friday.
The ridge will shift east Friday night with an upper level trough
over the area for the weekend. The trough will move east Monday
with a weaker trough for Tuesday. Another upper level ridge
beginning to build Wednesday.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...Satellite imagery shows
clear skies over Western Washington this afternoon. Gusty
northerly winds behind a trough that moved by to the east earlier
have kept temperatures mostly in the 50s as of 3 pm/22z.

Upper level ridge building into the British Columbia coast
tonight with dry northerly flow aloft over the area. We do have a
geomagnetic storm in progress with the Kp index near 8 at 3 pm.
This classifies as a G4 category storm ( the scale goes from G1 to
G5 with G5 being the strongest ). The magnetic field is currently
pointing north which does not bode well for a northern lights
display in Western Washington. If the field turns south we could
get some northern lights later tonight. Weather will not be a
problem with clear skies into Thursday morning. Lows in the mid
30s to lower 40s.

Upper level ridge remaining over British Columbia Thursday with
dry northerly flow aloft over the area. Northerly winds will pick
up in the afternoon but will not be as strong as today. This
combined with a little warmer temperatures aloft will push highs
into the lower to mid 60s.

Upper level ridge axis sagging south Thursday night. The ridge
axis will be right over Western Washington Friday making it the
warmest day in the next seven days. Many locations in the
interior from Seattle southward will get into the lower 70s. This
will be the second 70 degree plus day of the month for Seattle and
the third one this year. Mid to upper 60s for the remainder of
the interior. Northwesterly winds off the cool ocean will keep
temperatures along the coast in the lower 60s. Lows Friday morning
in the mid 30s to lower 40s.

Upper level ridge shifting east Friday night with an upper level
trough moving into the area Saturday. Trough axis moving through
Western Washington Saturday morning bringing showers to the area.
With the increasing cloud cover Friday night lows will remain in
the 40s. Highs Saturday much cooler with the trough overhead, in
the mid to upper 50s.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Extended models in good
agreement with an upper level trough remaining over Western
Washington keeping showers and cool daytime highs in the forecast
Sunday. Trough moving east Monday with showers coming to an end. A
weaker trough arriving Tuesday. Not much moisture with this
feature. Low level onshore flow will keep high temperatures near
60. Upper level ridge building offshore Wednesday with
temperatures aloft warming a little. Northwesterly winds will
again limit high temperatures along the coast to the upper 50s.
For the interior upper 50s to mid 60s. With the clearing there
could be some frost problems Tuesday night/Wednesday morning.
Felton

&&

.AVIATION...Northwest flow aloft becoming northerly tonight and
Thursday. Subsidence aloft will aid in area-wide VFR throughout the
upcoming TAF period. Breezy northerly surface winds with gusts up to
25 kt this afternoon for terminals KPAE south towards KOLM. Winds
diminish after 02-04z Thursday becoming light overnight into
Thursday morning. As mentioned, VFR tonight through Thursday.
Northerly winds again pick up Thursday afternoon.

KSEA...VFR conditions through the TAF period. Northerly winds 10-15
kt with gusts up to 25 kt. Winds will decrease to 5-10 kt by 04-05z,
gradually becoming light overnight into early Thursday morning.
Winds pick up again Thursday afternoon.

McMillian

&&

.MARINE...Frequent northerly wind gusts up to 21 kt has prompted a
SCA for Puget Sound this afternoon through the evening. A brief
window of SCA gusts are possible as well over the coastal waters for
a few hours as well this evening along with current high seas.

High pressure will be lock-solid over the NE PAC for the next
several days. However, a weak front is forecast to sneak around it
late Friday night into Saturday. Here we could see the next round of
headlines. Another weak disturbance looks to arrive on Sunday. 10 to
12 ft seas will gradually come down tonight allowing the current
Grays Harbor and coastal water zones SCAs to expire. Seas down to 4-
6 ft on Thursday before rising above 10 ft on Saturday.

McMillian

&&

.HYDROLOGY...No river flooding the next 7 days.


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...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-Grays Harbor Bar.

     Small Craft Advisory until 10 PM PDT this evening for Puget
     Sound and Hood Canal.

&&

$$