Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

000
FXUS66 KSEW 101729
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
929 AM PST Sun Dec 10 2017

.SYNOPSIS...A strong upper ridge will maintain dry and stagnant
conditions across Western Washington through the middle of the
week. The ridge looks like it will break down mid week with the
first chance of rain Thursday or Thursday night. Another system
will follow the first one keeping at least a chance of rain in the
forecast into next weekend.

&&

.SHORT TERM...Fog coverage is less extensive this morning
compared to the past few days. This is due to passing, dense
cirrus clouds overnight which lead to less radiational cooling and
thus higher dewpoint depressions. The end result, just patchy fog
in the south sound. This means more sunshine across the region
today with temperatures this afternoon mainly in the mid to upper
40s. The coast will see 50s again. Skies should remain clear
tonight for more fog.

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 remain over the region on Tuesday for similar
conditions...aka dry. 33

.LONG TERM...Previous discussion...Extended models consistent in
the idea that the dry spell comes to an end after Wednesday. The
00z run is a little slower with the first system after the ridge
versus the 12z run but at this point will let the chance pops on
Thursday ride. All of the models have some precipitation Thursday
night. Beyond Thursday night it is back to our regularly scheduled
December weather with zonal flow aloft and a series of weather
systems taking aim at the area into next weekend. Felton

&&

.AVIATION...A strong upper level ridge will remain over the
region. Contd sw flow aloft and low level offshore flow. Patchy
LIFR CIGs/VSBYs over the south Puget Sound Region should dissipate
this afternoon. Expect areas of LIFR CIGs/VSBYs to develop over
the interior lowlands tonight. The absence of high clouds plus the
presence of the strong ridge and light winds should result in fog
being a little more widespread Monday morning.

KSEA...VFR conditions will prevail through much of tonight.
Dense fog is anticipated Monday morning. Winds will be light
northerly.

&&

.MARINE...Lower pressure offshore with a 1040 mb high over
northeast WA will keep the flow east or northeast today. Expect
the offshore flow to weaken on Monday. Light offshore flow will
then persist through midweek. Looking further ahead, it looks like
typical weather conditions for mid-December will return the later
this week.

&&

.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 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.

&&

$$

www.weather.gov/seattle



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.