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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS66 KSEW 301619
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
919 AM PDT Thu Mar 30 2023

.SYNOPSIS...
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A weak upper level trough will move across the region
late today, bringing a chance of showers to portions of western
Washington. A unseasonably strong frontal system will then move
across the area Friday night into Saturday, bringing gusty winds,
lowland rain, and periods of heavy mountain snow to the area. Cool
upper level troughing will remain over the region into early next
week for continued shower activity and below normal temperatures.
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&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
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Satellite imagery shows low
clouds along the coast and over the Lower Chehalis Valley and central
Puget Sound with high clouds over the central and southern
Cascades. Temperatures at 9 am/16z were in the lower to mid 40s.

Northwesterly flow aloft today and tonight with a weak upper level
trough moving through late this afternoon/this evening. Can`t rule
out a few showers with the trough but for the most part it will be
dry.

Main weather producer in the next week is a unseasonably strong
cold front that will reach the coast Friday night and move inland
early Saturday. Rain, mountain snow and breezy conditions ahead
and with the front. Winter storm watch is up for the Cascades
beginning 00z Saturday for snow in all the passes. Cold, unstable air
mass settling over Western Washington behind the front later Saturday
keeping showers in the forecast.

Current forecast looks good this morning. No updates. Felton

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Previous discussion
follows. Cool and unsettled weather will persist through much of
the extended period. An upper level low looks to swing through the
region Sunday into Monday, which will keep shower activity in the
forecast. With a cold airmass remaining in place, snow levels
will be rather low (between 400-600 ft) by early Monday morning.
Should enough moisture linger for any heavier shower activity,
cannot rule out a rain/snow mix for some lowland locations during
the early morning hours. Temperatures will remain unseasonably
cool Sunday and Monday, with highs generally in the 40s to low 50s
and overnight lows expected to dip into the low to mid 30s.

The upper level low looks to exit the Pacific Northwest to the
south and east on Tuesday and looks to be replaced by an upper
level ridge building into the region near midweek. The GFS and
ECMWF ensemble solutions continue to show a reduction in the
number of wet solutions for the period, but do still have 20-30
percent of the solutions showing some light precipitation. Thus,
showers remain in the forecast for both days for now, but do not
expect conditions to be as wet as over the weekend. Afternoon
highs will warm a few degrees each day - and will be in the 50s.
Overnight lows look remain in the 30s. 14
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&&

.AVIATION...
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Light northwesterly flow aloft will transition more
westerly tonight as an upper trough moves towards the area. MVFR low
clouds have spread into portions of the central Puget Sound this
morning with onshore flow. Slow improvement to VFR expected for most
areas in low clouds later this morning into the early afternoon.
MVFR may linger for the immediate coast. A few light rain showers
will be possible today mainly along the coast. MVFR cigs are likely
again later tonight into Friday with increasing rain potential and
breezy winds on Friday.

KSEA...MVFR cigs this morning with onshore flow. Cigs will improve
to VFR later this morning into the early afternoon. VFR this evening
with MVFR likely later tonight into Friday. Southwesterly winds
generally 7 to 12 kts. JD
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&&

.MARINE...
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Onshore flow through today with the strongest winds
through the central portions of the Strait of Juan de Fuca, a Small
Craft Advisory is in effect for this area. Increasing southerly
winds on Friday as a frontal system moves towards the area. Small
Craft Advisory winds are likely over all the waters Friday afternoon
into Friday night, a slight chance for gales across portions of
Admiralty Inlet and the Eastern Strait of Juan de Fuca. Winds will
remain elevated through the weekend with onshore flow. Seas of 4 to
6 feet today will subside to 2 to 3 feet on Friday, building into
Friday night and Saturday. JD
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&&

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

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Watch from Friday afternoon through Sunday
     afternoon for West Slopes North Cascades and Passes-West
     Slopes North Central Cascades and Passes-West Slopes South
     Central Cascades and Passes.

PZ...Small Craft Advisory until 11 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 11 AM PDT this morning for East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$