122
FXUS66 KSEW 231727
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
927 AM PST Sun Feb 23 2020
.SYNOPSIS...It will be windy today behind a cold front with
scattered showers, heavy mountain snow and a few thunderstorms.
Dry conditions will return briefly later Monday into early
Tuesday before a weak front brings few showers to the area Tuesday
and Wednesday. Another frontal system may bring rain to the area
late in the week or early next weekend.
&&
.SHORT TERM /TODAY THROUGH TUESDAY/...A pre-frontal squall line
brought a burst of wind, rain, and a few thunderstorms earlier
this morning but that has moved off to the east and weakened. A
cold front will continue to work its way inland this morning with
showers but also some sunbreaks. Winds will pick up again this
afternoon as strong onshore flow develops. No headlines are
expected for now but it will be quite blustery. There will also be
a more general slight chance of thunder today as an upper trough
moves over the area. The best chance for thunder should be this
afternoon. Lastly, snow will pile up in the mountains today and
tonight with difficult travel conditions expected.
Showers will become largely confined to the mountains tonight and
perhaps in a Puget Sound Convergence Zone near the King/Snohomish
county line. Snow levels will fall to a few hundred feet above
sea level by Monday morning. Showers should be isolated at most by
that time and lowland accumulations are not expected. The drying
trend will continue on Monday as high pressure aloft builds in
from the west. Monday night and the first half of Tuesday should
be largely dry as an upper ridge transits the area. Rain chances
will return later Tuesday, mainly coast and north interior, as a
weak front arrives. Schneider
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Previous discussion...A
weakening frontal system will be crossing the local area at the
start of the long term period. A few light showers may hang around
in its vicinity, but should gradually wane through the afternoon
hours. The upper level ridge will attempt to recover and deflect
the storm track to the north on Thursday, though a few showers may
still sneak into northern sections of the area. Even if the ridge
is successful in deflecting moisture northward, its presence will
be short-lived, as it appears troughing offshore will deepen late
in the week and early next weekend. This will likely bring a
frontal system our way.
Kovacik
&&
.AVIATION...Strong front in the Cascades at 18z with post frontal
onshore flow increasing this afternoon into this evening. Air mass
unstable this afternoon into the evening hours. Westerly flow
aloft becoming northwesterly this afternoon.
Ceilings mostly VFR into Monday morning with a scattered to broken
layer around 4500 feet. Scattered showers with ceilings lowering
to near 2000 feet in the showers through 06z. Developing
northwesterly flow aloft will keep shower activity out of the
central Puget Sound for the most part. Convergence zone developing
north of KPAE with ceilings near 1000 feet and visibility 3-5sm in
moderate rain showers.
KSEA...VFR ceilings for the most part. Showers moving inland could
drop ceilings briefly down to near 2000 feet until around 22z.
Southerly winds 12 to 18 knots gusting to 25 to 30 knots until
around 06z. Felton
&&
.MARINE...Strong onshore flow developing behind the Sunday morning
front over the waters this afternoon with the strong onshore flow
continuing until Monday morning. Gale force winds along the coast
and Strait of Juan de Fuca and waters in the vicinity of the East
Entrance to the Strait into early Monday morning with small craft
advisories for the remainder of the waters. Onshore flow will ease
Monday with a surface ridge of high pressure building inland.
The high will remain over the area on Tuesday. A weak front will
dissipate over the waters Tuesday night into Wednesday.
Seas over the Coastal Waters will briefly build to 20-24 feet this
afternoon and evening before subsiding again by early Monday
morning. A high surf advisory remains in effect. Felton/14
&&
.HYDROLOGY...River flooding is unlikely for the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning until 4 AM PST Monday for Cascades of
Pierce and Lewis Counties-Cascades of Snohomish and King
Counties-Cascades of Whatcom and Skagit Counties.
High Surf Advisory from 1 PM this afternoon to 1 AM PST Monday
for Central Coast-North Coast.
Winter Weather Advisory until 10 PM PST this evening for
Olympics.
PZ...Small Craft Advisory until 6 PM PST Monday for Grays Harbor Bar.
Gale Warning until 1 AM PST Monday 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-West Entrance U.S. Waters Strait Of Juan De Fuca.
Gale Warning until 6 AM PST Monday for Central U.S. Waters
Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
Juan De Fuca.
Small Craft Advisory until 6 PM PST this evening for Admiralty
Inlet-Northern Inland Waters Including The San Juan Islands.
Gale Warning from 6 PM this evening to 1 AM PST Monday for
Admiralty Inlet-Northern Inland Waters Including The San
Juan Islands.
Small Craft Advisory until 6 AM PST Monday for Puget Sound and
Hood Canal.
&&
$$
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