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000 
FXUS66 KSEW 152208
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
208 PM PST Sun Dec 15 2019

.SYNOPSIS...Weak high pressure aloft will build over the area 
Monday and Tuesday. A warm front will brush western and northern
portions of the area Monday with some light rain. A broad upper 
level trough will develop over the northeast Pacific by midweek 
with a series of potent systems reaching the area into next 
weekend.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Scattered showers will
gradually dissipate over the area this evening as weak upper level
ridging starts to build into the area. Still a lot of low level
moisture continues to linger around the region. With light surface
winds, patchy fog is likely to form in the more fog prone valleys
overnight. Higher level clouds associated with a weak warm front 
offshore are already close to the coast and will spread into the
region later tonight. Some light rain associated with the warm
front is expected to reach coastal areas and perhaps the north
interior Monday. The remainder of the area should remain 
generally dry Monday and Tuesday. The air mass dries out somewhat 
on Tuesday as cross-Cascade easterly flow picks up. This should 
help limit fog coverage and give some areas at least some partial 
sunshine. A broad upper trough will deepen over the northeast 
Pacific Tuesday night and Wednesday with the first of a series of 
systems spreading widespread rain and mountain snow across the 
area on Wednesday.

.LONG TERM /THURSDAY THROUGH SUNDAY/...The extended forecast
period continues to look like an active string of weather for the
region. Deterministic model runs funnel a fairly significant 
stream of moisture into the region. Snow levels look to remain 
relatively low through much of period and this translates to some
significant snowfall in the mountains in the run-up to the 
Christmas holiday period. 7 day precipitation anomalies of both 
the GFS and Euro show some positive values of 1 to 3 inches for 
the region. This is leaning toward a decidedly wetter period from 
what we've seen recently. 27

&&

.AVIATION...A weak upper trough will be replaced by an upper ridge 
through Monday. NW flow aloft. Isolated showers should come to an 
end this evening. There will again be patches of fog and low 
clouds tonight. A warm front will clip the area on Monday for some 
areas of light rain on the coast in the morning.

KSEA...Skies have not cleared much today around Seattle so the moist 
and stabilizing air mass will probably lead to some low clouds 
tonight. Mid and high clouds from a warm front brushing the area 
later tonight will help to keep radiational cooling from letting 
much fog set up.

&&

.MARINE...A warm front will clip the area on Monday. After the warm 
front brushes by gradients will become more easterly on Tuesday. Two 
or three frontal systems will affect the area Wed-Sat.

&&

.HYDROLOGY...There are no flooding concerns through the first 
half of this week. The latter part of this week will be wet, but
snow levels will be relatively low. There will be some rises on
the rivers. The Skokomish in particular will bear some watching. 

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 7 PM this evening to 4 PM PST Tuesday 
     for Coastal Waters From Cape Flattery To James Island 10 To 
     60 Nm-Coastal Waters From James Island To Point Grenville 
     10 To 60 Nm-Coastal Waters From Point Grenville To Cape 
     Shoalwater 10 To 60 Nm.

     Small Craft Advisory until 5 AM PST Monday for Grays Harbor Bar.

     Small Craft Advisory from 1 AM Monday to 4 PM PST Tuesday for 
     Admiralty Inlet-Coastal Waters From Cape Flattery To James 
     Island Out 10 Nm-Coastal Waters From James Island To Point 
     Grenville Out 10 Nm-Coastal Waters From Point Grenville To 
     Cape Shoalwater Out 10 Nm-East Entrance U.S. Waters Strait 
     Of Juan De Fuca-Northern Inland Waters Including The San 
     Juan Islands.

     Small Craft Advisory from 1 AM to 4 PM PST Monday for West 
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

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