100
FXUS66 KSEW 150419
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
919 PM PDT Tue Oct 14 2025

.UPDATE...Only update for the evening is an added frost advisory
tomorrow morning for portions of south Puget Sound, south interior,
the north coast along the west/central Strait of Juan de Fuca areas,
and the Hood Canal areas. The remainder of the forecast is on track
through the rest of the week and weekend. Previous discussion
follows with updated aviation section. HPR

&&

.PREV DISCUSSION... /issued 236 PM PDT Tue Oct 14 2025/

.SYNOPSIS...An upper level ridge will continue to provide dry
conditions along with seasonal daytime temperatures and cool
nights through Wednesday. A weakening front will lead to a chance
of a little rain later Thursday into Friday before a stronger
system arrives over the weekend with rain, wind, and mountain
snow.

.SHORT TERM /TONIGHT THROUGH FRIDAY/...An upper trough over
central and southern California will shift eastward into the Great
Basin on Wednesday allowing the ridge offshore to shift a little
closer to Western Washington for more sunshine and a modest bump
in temperatures. Surface gradients will be light by Wednesday
morning which should allow for a little more morning fog coverage
across south Puget Sound and the Southwest Interior.

The offshore ridge starts to flatten Wednesday night into Thursday
in response to an upper trough entering the Gulf of Alaska. This
will allow a weakening front to reach Western Washington Thursday
night into Friday. The front will have minimal impact by the time
it reaches the area with only a few hundredths of QPF expected across
the lowlands east of the Olympic Peninsula.

.LONG TERM /SATURDAY THROUGH TUESDAY/...While the initial front
won`t have much in the way of impact, it will, however, set the
stage for a more active pattern this weekend. The offshore ridge
is expected to give way as a 150+ knot jet stream carves out a
broad upper trough over the northeast Pacific. This is expected to
push a relatively strong frontal system into the area Saturday
night into Sunday. Snow levels will be initially high in the
warm sector of the system. Ensembles show a considerable spread in
the QPF amounts with this system, but there`s enough concern to
warrant a day 5 Excessive Rainfall Outlook from the Weather
Prediction Center for portions of the Olympic Peninsula. Snow
levels are expected to fall back to the higher passes behind the
front on Sunday.

Ensemble height anomalies lend a high degree of uncertainty to
the forecast Monday and beyond. As such, a generic "chance of
showers" forecast is a good compromise at this time.

27

&&

.AVIATION...Upper level ridge nosing into Southern British
Columbia with upper level low over the Great Basin giving
northerly low aloft over the area. Northerly flow in the lower
levels becoming onshore Wednesday evening. Clear skies through
Wednesday. While gradients will be weaker tonight with calm
winds, the risk for fog remains very low due to dry dewpoints
still in the region with the northerly low level flow. If any fog
forms, it is likely that it will be patchy in nature and mostly
confined to river valleys and the Southwest Interior.

KSEA...Clear skies through Wednesday. Northeast wind 10 to 15
knots becoming 6 to 10 knots after 11z. Winds switching to
southerly 4 to 8 knots after 03z Thursday. Felton

&&

.MARINE...Northerly or weak offshore flow across the waters will
weaken tonight as an area of low pressure to south of the area
departs and an offshore surface ridge expands into the coastal
waters. A weak front will arrive Thursday night into Friday with
little to no impact. A much stronger frontal system will reach
the waters Saturday night into Sunday with headlines expected for
most of the waters. Coastal seas will build into the double digits
this weekend and could exceed 15 feet by later Sunday.  27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Frost Advisory from 2 AM to 9 AM PDT Wednesday for Eastern
     Kitsap County-Eastern Strait of Juan de Fuca-Lake Crescent
     Area Including US 101-Lowlands of Pierce and Southern King
     Counties-Northern Washington Coast-Western Strait of Juan
     de Fuca-Willapa and Black Hills.

PZ...None.
&&

$$