Washington State Forecast Discussion

Western Washington


684
FXUS66 KSEW 030001 CCA
AFDSEW

Area Forecast Discussion...CORRECTED
National Weather Service Seattle WA
401 PM PST Mon Dec 2 2024

.SYNOPSIS...High pressure will continue to amplify into western
Washington into early this week, allowing for dry conditions and
periods of morning fog and low stratus. The upper ridge will weaken
towards the middle of next week as the next storm system approaches,
bringing in the next chance for widespread precipitation across the
region.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...High pressure remains in
control through Wednesday for an extended period of dry and stable
conditions. Light winds and poor mixing is leading to stagnant
conditions in the interior where low clouds and fog linger. As a
result, temperatures remain cool and in the 30s and 40s. It's
sunny up in the mountains, though. Low clouds will settle again
overnight with dense fog possible for the Tuesday morning commute.
Freezing fog is also possible, especially around the south sound.
A trough will override the ridge on Thursday with a period of
light rain. Winds and mixing will also increase, helping to scour
out the low level air mass. 33

.LONG TERM /FRIDAY THROUGH MONDAY/...A warm front clips the area
on Friday for rain and high elevation snow (snow levels
7000-9000ft). Western WA is in the warm sector with mild highs in
the 50s. Low temps will also remain above freezing. A baroclinic
band shifts S/SE into western WA on Saturday for more rain and
heavier mountain rain/snow. Snow levels will lower to around
3000-3500 ft by Saturday night. We're under cool NW flow Sunday
and Monday with showers mainly impacting the Cascades (heavy
snowfall possible in the North Cascades). A ridge brings drier
weather moving into Monday, with a break in the precip noted in
the ensemble members. 33

&&

.AVIATION...Visibilities have gradually started to improve
across some of the terminals into VFR/MVFR. Some terminals
experienced some temporary improvement, but have now returned back
to IFR/LIFR conditions. Some terminals (KPWT, KPAE, KOLM) have
remained in IFR/LIFR conditions throughout the day. It is likely
these terminals will not see much improvement through the daylight
hours as conditions are expected to worsen shortly after the sun
sets around 0Z. Expect widespread fog and visibilities that may
decrease below 1 mile. Conditions should improve back to VFR once
the sun comes out around 21Z. However, confidence is low at this
time at how quickly the fog will dissipate.

KSEA...After some temporary improvement, MVFR conditions have
settled in at the terminal and are expected to go back to LIFR as
early as 3Z on Tuesday. As of now, the fog is expected to lift
around 21Z. However, based on how slow the fog was to dissipate
throughout the day on Monday, it is likely the fog may linger
shortly past 21Z.

MGF

&&

.MARINE...High pressure will remain situated over the Pacific
Northwest through midweek. This will lead to widespread fog and
limited visibility less than 1 NM possible. Waves will be
generally be between 5 to 8 ft over the coastal waters. A series of
weather systems will begin to impact the area on Thursday. A much
stronger system begins to move through on Friday that may lead to
waves between 10-15 ft along with stronger winds.

MGF

&&

.HYDROLOGY...An upper ridge will remain in place across Western
Washington through Wednesday. A frontal system will move through on
Thursday for lighter QPF amounts. Another weather system Friday into
Saturday is forecast to bring heavier QPF amounts. In addition, snow
levels are expected to rise later Friday into early Saturday to 7000
to 9000 feet. This, combined with rainfall, will result in rises on
rivers across Western Washington. At this time, the Skokomish River
is the main river of concern for potential river flooding during
this period. However, other area rivers will need to be monitored
due to the higher snow levels Friday into Saturday. JD

&&

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