Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 241011

Area Forecast Discussion
National Weather Service Seattle WA
311 AM PDT Fri Mar 24 2023

.SYNOPSIS...An active pattern will remain over Western Washington
Friday through the weekend with an upper level trough over the
area. In addition to mountain snow, colder temperatures will
leave the door open for at least a chance of a wintery mix of
precipitation in the late night and early morning hours into
Sunday. Drier weather is in store early next week.


.SHORT TERM /TODAY THROUGH SUNDAY/...More showers are expected
across western WA today and tonight with strong onshore flow and
a cool upper low overhead. The air mass is slightly unstable with
a chance of thunderstorms, especially near the coast. Up in the
mountains, snow levels remain low (around 1500 ft) with more
accumulating snow possible at all Cascades highway passes - a
Winter Weather Advisory remains in effect. With the cool air mass
in place, temperatures will fall below average.

The air mass will remain cool and showery as we move into
Saturday although total precipitation amounts will be lighter.
Snow levels Saturday morning will be quite low (500-1000 ft) and
we may see a rain/snow mix at times in the lowlands. However,
significant and/or widespread accumulations are not expected.

Western WA is in between systems on Sunday but we`re still under
a broad trough that covers much of the West. There`s still a
little moisture and lift over the area but the overall consensus
in the ensemble guidance is that precipitation amounts will be
light. A few cloud breaks will help nudge temps upwards with highs
near 50. 33

.LONG TERM /MONDAY THROUGH THURSDAY/...Model ensemble guidance
points toward drier weather as we move through early next week.
This is due to a strong system offshore that shifts inland to our
south Monday and Tuesday. The low level flow pattern will be
turning offshore for less cloud cover. This will help temperatures
climb closer to normal with highs in the mid 50s. Lows will still
be cool, though, and in the 30s. An upper ridge keeps drier
weather in the forecast as we move into mid week. The ridge then
flattens and the flow turns more zonal toward the latter half of
the week with a return to a wetter pattern possible. 33


.AVIATION...Upper level trough will remain over western Washington
today, with west to southwesterly flow aloft. The air mass is
moist and somewhat unstable. Latest radar shows scattered shower
activity across the region early this morning, resulting in a mix
of MVFR and VFR conditions across the terminals. Overall, expect
conditions to lower and become more widespread MVFR by daybreak.
MVFR conditions then look to persist into the afternoon hours,
with shower activity expected to be ongoing throughout the day.
May see some improvement for terminals to VFR this afternoon,
however expect those in shower activity to remain MVFR and even
IFR at times. A PSCZ looks to develop across the central Sound
this afternoon and persist into this evening. W/SW surface winds
will increase across the region again this morning, becoming gusty
to 20-25 kts at times.

KSEA...MVFR ceilings persist across the terminal this morning and
are expected to remain MVFR into the afternoon. A PSCZ may drift
over the terminal during the afternoon hours, temporarily reducing
cigs and visibilities further. Expect improvement back to VFR by
late afternoon (likely between 23-02Z). Surface winds will persist
from the SW at 10-15 kts, becoming gusty to 20 kts at times through
the day. 14


.MARINE...A surface trough will move inland today, keeping onshore
flow breezy across the area waters. As such, small craft advisories
remain in effect for the majority of the area waters this morning,
except for the central and eastern Strait of Juan de Fuca, where
another round of gales are likely this afternoon and evening - and
where a gale warning is now in effect. Onshore flow will continue
across the area waters this weekend, but will be weaker, with
surface high pressure residing well offshore and with lower
pressure inland east of the Cascades. Flow will then turn offshore
early next week as a low digs southward over the offshore waters.

Seas will continue to build to 14-17 feet across the coastal
waters today and will remain elevated into Saturday, before
gradually subsiding back below 10 feet late in the weekend. 14


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


WA...Winter Weather Advisory until 5 AM PDT Saturday for West Slopes
     North Central Cascades and Passes-West Slopes South Central
     Cascades and Passes.

PZ...Small Craft Advisory until 5 AM PDT Saturday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville Out 10
     Nm-Coastal Waters From Point Grenville To Cape Shoalwater
     10 To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm-Grays Harbor Bar-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning from 9 AM this morning to 7 PM PDT this evening for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 11 PM PDT this evening for Admiralty
     Inlet-Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory until 5 AM PDT early this morning for Puget
     Sound and Hood Canal.


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