Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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376
FXUS66 KSEW 102308
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
308 PM PST Sun Dec 10 2017

.SYNOPSIS...A strong upper ridge will maintain dry and stagnant
conditions across Western Washington through Wednesday. The ridge
will break down by Thursday with rain returning Thursday night
and Friday. Wet weather will continue through the weekend with
strong moist flow over the area.

&&

.SHORT TERM...Fog was limited today due to dense cirrus clouds
that passed before sunrise. As a result, there was less
radiational cooling and therefore higher dew point depressions.
The visible satellite shows some patchy clouds or fog over Hood
Canal otherwise the rest of the region is sunny. Temperatures are
mainly in the 40s with 50s along the coast. Looks like
Quillayute, KUIL, hit 59 degrees which is a new daily record
high. Skies should remain clear tonight with fog reforming around
Puget Sound.

The dry conditions, light winds and poor mixing has lead to
stagnant conditions. This may result in deteriorating air
quality. An Air Stagnation Advisory remains in effect for the
interior lowlands - burn bans are possible.

There`s a slight change in the pattern on Monday when a shortwave
trough clips the NW portion of the ridge, slightly flattening the
heights over W WA. This features is dry but we could see a bit
more mixing with a weaker low level inversion. The strong ridge
will rebuild over the region Tuesday and Wednesday for similar
conditions...aka dry. The biggest forecast challenge will again
be fog coverage and temperatures. 33

.LONG TERM...It looks like Thursday will be our last dry day of
this stretch as the ridge will start to break down. We should see
rain returning by Thursday night or Friday as a trough moves in
from the west. The models have been waffling on the exact timing
of this system and it`s now slightly slower compared to
yesterday`s (faster) solutions. Moist west to northwest flow will
continue trough the weekend for more wet weather with snow in the
mountains. 33

&&

.AVIATION...A strong upper level ridge will remain over the
region for sly flow aloft. The low level flow will be light
offshore. Expect areas of LIFR CIGs/VSBYs to develop over the
interior lowlands overnight, continuing thru at least Monday
morning.

KSEA...Still expecting VFR conditions to prevail through much of
tonight. A few hours of dense fog is anticipated Monday morning.
Light northerly winds will become light and variable Monday
afternoon.

&&

.MARINE...Lower pressure offshore with higher pressure inland
will result in light easterly or offshore flow through midweek.
Expect a cold or occluded front to move across the area late
Thursday night or early Friday. This will cause the flow to become
onshore and strengthen.

&&

.HYDROLOGY...River Flooding is not expected for the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Air Stagnation Advisory until noon PST Monday for Admiralty
     Inlet Area-Bellevue and Vicinity-Bremerton and Vicinity-
     East Puget Sound Lowlands-Eastern Strait of Juan de Fuca-
     Everett and Vicinity-Hood Canal Area-Seattle and Vicinity-
     Southwest Interior-Tacoma Area-Western Skagit County-
     Western Whatcom County.

PZ...Small Craft Advisory until 2 AM PST Monday 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 9 AM PST Monday for Coastal Waters
     From Cape Flattery To James Island Out 10 Nm-Coastal Waters
     From Point Grenville To Cape Shoalwater Out 10 Nm-West
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

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