484
FXUS66 KSEW 252212 AAA
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
206 PM PST Sat Jan 25 2025

.SYNOPSIS...An upper level ridge centered offshore will gradually
build into the region through the early portion of the coming
week. This will lead to dry conditions and chilly overnight
temperatures. The ridge will weaken by midweek and a series of
systems will bring a return of lowland rain and mountain snow
Thursday into next weekend.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...An upper ridge centered
offshore and north-northeasterly flow at the surface and aloft
have led to a crisp, dry mid-winter day across Western Washington.
This general pattern will remain fairly static heading into Sunday
and Monday. Surface gradients turn lighter over time and this will
likely contribute to more patchy freezing fog across the
Southwest Interior, south Puget Sound, and outlying river valleys
over the next couple mornings. Overnight lows will remain on the
chilly side. Tonight`s forecast lows were edged downward closer
to the 25th percentile of the NBM. For the most part, this keeps
most spots just above cold weather advisory criteria, but it
wouldn`t be surprising to see Olympia dip below the 20F threshold
once again Sunday morning. Upper ridging begins to weaken more
noticeably by Tuesday...signaling a coming shift from the
persistently dry pattern of the past nearly two weeks.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Model agreement with
the turn toward a cool unsettled pattern in the second half of the
week is good, but ensemble agreement with respect to the depth and
track of an expected upper trough trails off pretty quickly by
next weekend. And that could have implications in terms of both
precip type and amounts by Saturday. The mountains will certainly
get several inches of snow, but it`s also worth mentioning that
lowland snowfall probabilities are creeping upward. The NBM is now
putting a good swath of the interior lowlands in the 20-40%
chance of a fraction of an inch snow by late Saturday...which is
up from generally 20% or less as of yesterday. It`s still early
yet, but definitely something that we`ll be monitoring. 27

&&

.AVIATION...Northerly flow continuing aloft and at the surface this
afternoon with VFR cigs prevailing. Winds have increased a bit above
expectations in central Puget Sound, with other locations generally
reporting winds in the 5 to 8 kt range. The VFR cigs and northerly
winds are expected to continue overnight and into tomorrow morning.
Models are not suggestive of fog or stratus to impact main terminals
overnight. There could be some pockets of freezing fog near OLM and
the coast overnight.

KSEA...North winds have picked up to between 10 and 14 kts this
afternoon. Have opted to carry this trend to around 05Z before the
speeds drop down to the 5 to 7 kt range. Northerlies as well as VFR
cigs are expected throughout the rest of the afternoon and into the
overnight hours. Another increase out of the north to 7 kts likely
early tomorrow afternoon.

Kristell

&&

.MARINE...Surface ridging strengthens over interior British
Columbia and east of the Cascades today while a broad surface trough
deepens well to the south over California. This will lead to
northerly or weak offshore flow. This general pattern remains in
place into early next week. The next front will approach the coastal
waters around the middle to later half of next week.

Seas 5 to 6 ft for much of the weekend. Seas will ease further, down
to 3 to 5 ft, Monday and remain that way into the middle of next
week, rising again ahead of the aforementioned front that is likely
to arrive Thursday night. Timing on that front may vary as the
models struggle sometimes with pattern changes after prolonged
ridging, but nevertheless, a return to some marine headlines may be
warranted.

Kristell

&&

.HYDROLOGY...No river flooding is expected in the next 7 days.

&&

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

$$