FXUS66 KSEW 171632
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
833 AM PST Sun Jan 17 2021

.SYNOPSIS...An upper level ridge will set up over the area with dry
conditions through at least Tuesday. A weak disturbance may clip the
area Tuesday night. The next disturbance arrives later in the week,
likely ushering in a cooler air mass.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...No updates this morning.
High pressure and offshore flow will lead to dry conditions
through Tuesday. We`ll likely see areas of low clouds or fog
during the morning hours, especially near the sound. Lows will dip
into the 30s again with highs mostly around 45-50. A weak system
may track S/SW from B.C. on Tuesday night for a chance of
showers, mainly in the north Cascades. This is a quick-moving
system and precipitation amounts look rather light.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...High pressure and
offshore flow will continue into Wednesday leading to cooler and
drier conditions. Late in the week, next Thursday or Friday, a
trough will dig offshore which may spread moisture into western
WA. Precipitations amounts look light with just a few hundredths
of an inch over the lowlands. Snow levels will be low, around
1500-2000 ft, and could see light rain/snow mix in areas near the
Cascades.

Our cool period will continue into the weekend with low snow
levels and overnight temps near freezing. ECMWF and GFS ensemble
members show potential for lowland snow (Sunday or Sunday night)
but amounts look spotty and light. It`ll all depend on timing
(snow levels, moisture, temperatures) which is all still
uncertain. 33

&&

.AVIATION...Westerly flow aloft becoming northwesterly by late
morning as an upper level ridge builds offshore. Low level onshore
flow increasing this morning with the onshore flow pattern
continuing into the afternoon. Light low level flow tonight into
Monday morning. Continuation of onshore flow will limit much in the
way of ceiling and visibility improvements across the region today.

Front moving through interior at 10z with ceilings 4000-5000 feet
ahead and with the front and 1000-1500 feet with local ceilings
below 1000 feet and visibility 3-5sm in fog behind the front.
Post frontal conditions will spread over the entire area 14z-18z
this morning. Improving trend late afternoon with ceilings rising to
3500-4500 feet. Ceilings lowering back down to below 1000 feet with
local visibility 1-3sm in fog after 09z tonight.

KSEA...Ceilings near 4000 feet lowering to 1000-1500 feet 14z-18z.
Ceilings improving after 22z to 3500-4500 feet by 02z. Ceilings
lowering back down below 1000 feet after 09z tonight. Southerly wind
6 to 10 knots becoming northerly 4 to 8 knots around 00z.
Felton/Kristell

&&

.MARINE...High pressure will build over the waters today and
remain in place through Monday night. A weakening system will arrive
Tuesday. High pressure will rebuild Wednesday and Wednesday night.
Another system will arrive Thursday.

Small craft advisory west winds developing in the Central and
Eastern Strait of Juan de Fuca this morning. Westerlies easing late
this afternoon. Small craft advisory west winds possible behind the
front over the coastal waters Tuesday night.

Westerly swells remaining in the 11 to 15 foot range through Monday.
Swell subsiding Monday night with swells around 7 feet Tuesday.
Felton


&&

.HYDROLOGY...No river flooding is expected in the next 7 days. The
lower reaches of the Chehalis river will continue to run high
from Montesano down to Grays Harbor this morning. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 4 PM 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-Grays Harbor Bar-West Entrance U.S.
Waters Strait Of Juan De Fuca.

Small Craft Advisory from 8 AM this morning to 4 PM PST this
afternoon for Central U.S. Waters Strait Of Juan De Fuca-
East Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

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