362
FXUS66 KSEW 011749
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
949 AM PST Mon Dec 1 2025

.SYNOPSIS...
Weak weather systems moving down the backside of an
upper level ridge offshore will move through Western Washington
the next few days. One will arrive this morning with another
one later tonight into Tuesday. A third weak system will arrive
Thursday. The ridge offshore will weaken Thursday night opening
the door for a series of stronger systems to reach the area
Friday into the first part of next week.

&&

.UPDATE...
Generally quiet conditions across the region this morning.
Little to no impactful weather is expected today. The current
forecast is on track and no updates are planned this morning.
-Wolcott-

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Satellite imagery shows weak upper level ridge off the coast
with a weak weather system moving down the backside of the
ridge through British Columbia. High clouds over the area. Clear
skies Sunday evening allowed fog to form over the Southwest
Interior with visibility at Olympia and Chehalis a half mile or
less at 3 am/11z. Temperatures were mostly in the 30s.

Weak system moving through Western Washington this morning.
Doppler radar is picking up some echoes over the Northwest
Interior but with cloud heights above 10000 feet very little if
any of the precipitation is reaching the ground. This will
continue to be the case as the system moves through the area.
With temperatures near freezing in the Northwest Interior if any
precipitation does reach the ground in the next few hours could
see a few snow flakes/flurries in both Whatcom and Skagit
county. For the remainder of the area just a chance of light
rain. Fog in the Southwest Interior will dissipate later this
morning. Cloud cover will keep high temperatures in the mid 40s.


Another system will follow the same track tonight moving into
the area overnight into the early morning hours. This system is
a little stronger than the one this morning and actually carves
out a bit of a trough with it. Likely pops common across the
area but rainfall amounts will be light, less than a tenth of an
inch for most locations. Cloud cover will keep temperatures from
dropping tonight into Tuesday morning with lows just a few
degrees below the highs, upper 30s to mid 40s.

System moving out of the area from north to south later Tuesday
morning into Tuesday afternoon. Dry afternoon from Seattle
northward. Not much clearing behind the front keeping skies
mostly cloudy in the afternoon. Best chances for a little
clearing along the North Coast. Highs in the mid 40s to lower
50s.

Upper level ridge offshore nosing into the British Columbia
coast Tuesday night and Wednesday with dry northerly flow aloft
over Western Washington. Light flow in the lower levels combined
with the ridge axis offshore will keep skies mostly cloudy. The
cloud cover will limit fog formation with just patchy fog in
the fog prone locations like the Southwest Interior Tuesday
night and wednesday morning. Lows in the mid 30s to lower 40s.
Cloud cover will also keep high temperatures down, mostly in the
mid 40s.

November in Seattle was a warm one. The average monthly
temperature of 48.6 degrees was 2.1 degrees above normal. This
is the 7th warmest November in 81 years of records. The normal
average temperature in Seattle for December is 42.0 degrees. In
the top 10 warmest Novembers not including this year 8 out of
the 10 Decembers had an average temperature below 42.0 degrees.
Felton

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Extended models and ensembles in good agreement with another
weak system moving down the backside of the ridge into Western
Washington Thursday. Ridge offshore weakening Thursday night
opening the door to a series of stronger systems. The first
one arriving Friday with another later in the weekend. The
system on Friday could tap into some sub tropical moisture. Air
mass over the area not excessively warm, snow levels in the 5000
to 6000 foot range, keeping some of the precipitation in the
mountains in the form of snow. Snow levels slowly lowering over
the weekend and could be below the higher passes for the round
of precipitation later in the weekend. High temperatures in the
40s Thursday will warm a little into the lower 50s for the
remainder of the period. Felton

&&

.AVIATION...
West to northwest flow aloft will continue with an upper level ridge
centered well offshore. A weak frontal system will reach the area
tonight with deteriorating ceilings and areas of light
precipitation. With the exception of IFR/MVFR stratus across
portions of the Southwest Interior this morning, VFR ceilings will
prevail into this afternoon. Ceilings will lower to MVFR overnight
as light precipitation spreads into the region. A mix of MVFR and
IFR will prevail areawide on Tuesday with light surface flow and a
moist air mass in place.

KSEA...VFR ceilings will lower to MVFR tonight as a weak system
spreads some light rain across the area. Precipitation will
dissipate on Tuesday, but low MVFR or occasional IFR ceilings will
persist throughout the day tomorrow. Light and variable surface
winds will become southerly 7 knots or less tonight, then return to
light and variable or very weak northerly during the day on Tuesday.

27

&&

.MARINE...
High pressure will move out of the region today as a weak
system moves over the waters today through Tuesday with showers.
Northwest winds behind the system Tuesday will increase in the
coastal waters with winds of 15-25 kt (especially in the outer
coastal waters). Seas will also increase from 4-6 ft Monday to 9-12
ft Tuesday through Wednesday. Benign conditions are expected behind
this system, with light winds, and seas returning to 4-6 ft. A
stronger system Friday through the weekend may bring small craft
advisory level winds to the coastal waters, and a few of the north
interior waters. There is also a medium chance at this time for gale
winds in the Strait of Juan de Fuca. Seas will also increase to 9-13
ft with this system Friday through the weekend into early next week.

HPR

&&

.HYDROLOGY...
System reaching the area around Friday looks to possibly have
some sub tropical moisture entrained with it. The pattern is
progressive and snow levels are not excessively high, 5000 to
6000 feet. River flooding is not expected over the next 7 days.

November rainfall for Seattle was 5.71 inches, 0.60 inches
below normal. Only March and August have had above normal
rainfall this year. The yearly rain total for Seattle through
November 30th is 25.68 inches. The 8th driest January through
November in 81 years of records and the driest since 2002 with
25.38 inches. There have only been 6 years since records started
in 1945 where the yearly rainfall total in Seattle has been
less than 30 inches. The last time was 2000 with 28.66 inches.
Felton

&&

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

&&

$$