Deckerville, Washington Weather Forecast Discussion

095
FXUS66 KSEW 090335
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
835 PM PDT Mon Sep 8 2025
.SYNOPSIS...Upper level low just offshore will push inland tonight
into Tuesday. The low will weaken but remain in the area through
Friday. A splitting system will try to move into the area during
the latter half of the weekend.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...A few
thunderstorms developed over the North Cascades this evening and
have started to dissipate over the last hour. In addition,
showers and thunderstorms continue to track northwards in
northern Oregon, primarily over the Cascades. This convection is
expected to continue into Washington tonight, although it may
slowly dissipate as it does so. With that said, showers, along
with a slight chance of thunderstorms, will be possible later
tonight across the southern Cascades, mainly around Mt. Rainier.
Will need to monitor if any showers drift westwards into Puget
Sound into early Tuesday morning. No major forecast updates
this evening. Previous discussion below.
Satellite imagery shows large upper level low off the coast
with the low center just west of Crescent City. Doppler radar
has a few showers over Skagit and Whatcom county with the
precipitation mostly likely not reaching the ground in most
locations. Some clearing over the southern portion of the area
has allowed temperatures to climb into the mid to upper 70s.
Temperatures mostly in the mid 60s to lower 70s over the
northern portion of the area and along the coast.
Upper level low slowly moving east overnight. With the low center
so far south not much in the way of dynamics over Western
Washington. Air mass somewhat unstable over the Cascades so will
keep a chance of showers with a slight chance of thunderstorms
until a couple hours after sunset. For the remainder of the area
varying degrees of cloud cover. Light onshore flow tonight with
stratus forming along the coast spreading inland early Tuesday
morning. Lows tonight in the 50s.
Light onshore flow Tuesday morning with areas of stratus to start
the day. Stratus retreating back to the coastline by midday. Upper
level low slowly moving inland but like this evening little in
the way of dynamics over Western Washington. Afternoon heating
with a slightly unstable air mass will create a chance of showers
from about the Puget Sound eastward. Highs will be near normal,
mid 60s to mid 70s.
Upper level low stalling over the Pacific Northwest Tuesday night
through Thursday. Low level flow remaining light onshore for more
rounds of morning stratus late light and morning hours with a
slight chance of showers in the afternoon and evening mainly
Puget Sound eastward. Slight chance of thunderstorms near the
crest Wednesday evening. Lows in the 50s. Highs both days in the
mid 60s to mid 70s.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...Some differences in the
models with respect to the timing of when the low kicks out of the
area. The GFS is a little faster moving the low into Idaho and
Montana. Even with the slower timing of the ECMWF chances for wrap
around moisture to get back into Western Washington are slim.
With the low still in the vicinity will keep slight chance pops
over the Cascades Friday with the best chances for showers late in
the day.
Low well to the east Saturday with a temporary ridge trying to
build over Western Washington while a frontal system tries to make
its way into the area. Blend has chance pops over the entire area
by Saturday night. Ensembles agree with less than 20 percent of
the solutions showing light precipitation Saturday night and a few
more solutions with precipitation Sunday. Blend keeps the chance
pops going into Monday while the operational runs build another
temporary upper level ridge into the area. Just enough ensemble
solutions to keep chance pops in the forecast but even the wet
solutions are very light with the precipitation. Will not be
surprised if future runs dry out the forecast for Monday.
Light onshore flow through the period will keep highs near
normal, upper 60s to mid 70s. Lows mostly in the 50s. Felton
&&
.AVIATION...An upper level low will move inland over OR tonight into
early Tuesday with light south to southeasterly flow across the
area. Lots of high clouds over the area with some stratus along the
northern coast. Status looks to redevelop along the coast and push
inland through the Strait of Juan de Fuca and through the Chehalis
gap, with IFR cigs or lower for BLI, HQM, and CLM. Period of reduced
visibility due to fog will also be possible at these locations.
Elsewhere across the interior, MVFR to locally IFR will be possible
as low-level moisture will allow low clouds to redevelop. Ceilings
should quickly raise and scatter in the morning on Tuesday, with the
exception of the coast where stratus will likely hang on into the
afternoon. Light, scattered showers look to develop Tuesday morning,
especially across the southeastern portions of the CWA, spreading
north across the area during the day. Chances for thunderstorms over
the Cascades Tuesday afternoon. Mostly light winds area-wide
tonight, with north to northwest winds 10 kt or less during the day
Tuesday.
KSEA...VFR conditions this evening with high clouds over the
terminal. Stratus will likely redevelop and lower early Tuesday
morning for a period of MVFR to potentially IFR (10-15% chance) from
around 13-17Z Tue before lifting and scattering to VFR late Tuesday
morning. Winds remain northerly 5 kt or less tonight, returning to
northwesterly 5-8 kt during the day Tuesday.
62
&&
.MARINE...Weak surface low pressure over the waters will remain in
place for the next few days with winds and waves remaining below
advisory thresholds. High pressure starts to build later in the
week, bringing a slight bump in winds and an a push of westerly
advisory winds is possible in the Strait of Juan de Fuca late
Thursday. Seas build to around 4 to 6 feet around Wednesday through
Friday. Another low pressure system could bring stronger conditions
into the weekend.
&&
.FIRE WEATHER...Thunderstorm chances will continue across the
Cascades in the late afternoon or evening hours through Wednesday
as an upper level low slowly moves over the Pacific Northwest.
The day with the highest probability for storm development will
be Tuesday but even on Tuesday it is less than 25 percent. Most
likely area in the Cascades will be the North Cascades. Primary
threats from any thunderstorms will be gusty outflow winds, brief
heavy downpours, small hail, and frequent lightning.
Outside of thunderstorm activity, increased moisture, cloud cover,
and seasonal temperatures will help to suppress fire weather
impacts into the first part of next week. Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$

NWS SEW Office Area Forecast Discussion