Crystal Mountain, Washington Weather Forecast Discussion

916
FXUS66 KSEW 092309
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
409 PM PDT Tue Sep 9 2025
.SYNOPSIS...An upper low south of the area will continue to
weaken and shift eastward. This will spread moisture into the
region, with showers and isolated thunderstorms developing near
the Cascades and moving into the region. Weak high pressure
Thursday and Friday will bring some drier conditions, but
another disturbance brings a return of rain to the region late
in the weekend.
&&
.SHORT TERM /TODAY THROUGH THURSDAY NIGHT/...As the upper low to
our south continues to advance very slowly eastward, we`re
seeing developing of showers and isolated thunderstorms. Expect
these mostly in the North Cascades and around Mt. Rainier this
afternoon and evening. The chance will remain into Wednesday
will less coverage and these confined mostly to just the high
Cascades as the best support continues to shift eastward.
Daytime highs Wednesday are not expected to change very much,
with the interior lowlands generally in the lower to mid
70s. This falls right around normal values for this time of
year.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...Models remain with out
consensus with regards to next incoming system. While most solutions
keep conditions dry Friday and even into Saturday morning, variances
emerge by Saturday evening where a few ensemble members prove to be
a little agressive in introducing PoPs. Additional members leaning
to an overnight Saturday solution but the slim majority seem to be
converging around Sunday morning, however even then differences of
opinion on the track of the incoming low will result in a wide array
of expected precip amounts. Thus, while PoPs do re-enter the
forecast Saturday through the remainder of the long term, mustering
anything more than a 50 pct chance could be a bit of a stretch. The
active weather will keep temperatures seasonable, with interior
lowlands seeing highs in the lower 70s and overnight lows in
the mid to upper 50s.
&&
.AVIATION...Mainly VFR with areas of MVFR/IFR in lingering low
stratus along the coast and northern interior between KPAE and KBLI.
Scattered showers and isolated thunderstorms will continue over the
Cascades today, but are not favored to move over the lowlands.
Onshore flow overnight into Wednesday morning will bring another
push of IFR/LIFR marine stratus and patchy fog  inland across
western Washington before conditions improve into Wednesday
afternoon...right around seasonable norms for this time of year.
Highs Thursday may even dip slightly below those norms, residing
in the upper 60s to lower 70s.
KSEA...VFR with passing mid and high clouds this afternoon and
evening. Light northerly winds will continue this afternoon, turning
more westerly this evening and becoming light and variable early
Wednesday morning. MVFR to IFR conditions will likely return around
10z-13z Wednesday morning, scattering out around 17z-19z for a
return to VFR conditions with scattered clouds Wednesday afternoon.
15
&&
.MARINE...Weak low pressure offshore today will shift inland on
Wednesday with a stronger onshore push down the strait Thursday
night - Small Craft Advisory winds are possible. Onshore flow will
also maintain periods of patchy fog over the coastal waters and
through the Strait of Juan de Fuca through the middle of the week.
High pressure will develop offshore on Friday. A weak front will
dissipate over the Coastal Waters this weekend.
Seas will generally remain between 4 and 7 feet into early next week.
15
&&
.FIRE WEATHER...Thunderstorm chances will continue across the
Cascades later this afternoon into the evening hours. An upper
level low will slowly move over the Pacific Northwest, keeping
a chance of thunderstorms in the forecast for Wednesday. The day
with the highest probability for storm development will be this
afternoon with chances ranging 20-35%, with the best chance for
thunderstorms being in the 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 continue to help suppress fire
weather impacts into the first part of next week.
Mazurkiewicz
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$

NWS SEW Office Area Forecast Discussion