Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 161627
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
827 AM PST Thu Feb 16 2017

.SYNOPSIS...A broad upper trough will bring cool and showery
weather to the area today. Weak high pressure aloft will bring
mostly dry weather Friday. A weather system will clip the area
Saturday. Wet weather will return for the first half of next week.

&&

.SHORT TERM...A front pushed inland earlier this morning. Post-
frontal showers will prevail today with easing winds. Snow levels
will fall to 4000-5000 feet and the mountains should pick up a few
inches of new snow. There are also some lingering flooding
concerns today. See the hydrology section below for details. Weak
high pressure aloft will build over the area on Friday for a
mostly dry day. A weather system mostly moving onshore to the
south will clip the area with a little rain on Saturday. Recent
models have trended a little more widespread with the
precipitation. Schneider

.LONG TERM...Previous discussion...A longwave trough over the
West will keep the weather pattern active through at least the
middle of next week. There is a chance of showers each period as
the models bring systems into the Pac NW. Temperatures will
continue to trend a few degrees below normal. We may see a break
late next week as a ridge over the NE Pacific shifts closer and
inland. 33

&&

.AVIATION...A front moved inland at daybreak and the air mass will
be moist and showery behind the front. Southwest flow aloft will
continue with low level onshore flow. Conditions will be variable
over Western Washington today due to leftover layers from the
frontal system, leftover low level moisture, and the showers.

KSEA...There will be scattered showers and sunbreaks today with a
vcsh and a southerly breeze. The mvfr cigs this morning will likely
break up by afternoon.

&&

.MARINE...A deep low is filling quickly as it moves into British
Columbia. There are small craft advisories in effect and today
should be breezy at times and showery. Winds will continue to ease
tonight with a weak surface low moving into the offshore waters. The
low will dissipate on Friday. Northerly pressure gradients will
develop later Friday then weaken late Friday night. Another weather
system will reach the area Sunday.

&&

.HYDROLOGY...Rivers flowing off the Olympics and north Cascades
have seen sharp rises from heavy rain the past 24-36 hours. So far
only one river, the Skokomish, is over flood stage. Not all rivers
have crested yet. A couple, like the Dungeness and Nooksack may
crest just under flood stage. Heavy rain has ended this morning
and most rivers will begin to gradually recede over the next day
or two. Otherwise, river flooding is not expected over the next 7
days.

The recent heavy rains have pushed USGS landslide guidance above
the threshold at which landslides typically occur. This means
another cycle of landslides is likely over the next few days. A
special weather statement is in effect to address this threat.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through this evening for Bellevue and Vicinity-
     Cascades of Snohomish and King Counties-Cascades of Whatcom
     and Skagit Counties-East Puget Sound Lowlands-Everett and
     Vicinity-Western Skagit County-Western Whatcom County.

     Flood Watch until 10 AM PST this morning for Admiralty Inlet
     Area-Central Coast-Eastern Strait of Juan de Fuca-Hood
     Canal Area-Lower Chehalis Valley Area-North Coast-Olympics-
     Western Strait of Juan De Fuca.

PZ...Small Craft Advisory for rough bar until 4 AM PST Friday for
     Grays Harbor Bar.

     Small Craft Advisory until 1 PM PST this afternoon 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.

     Small Craft Advisory until midnight PST tonight for East
     Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland
     Waters Including The San Juan Islands.

     Small Craft Advisory until 6 PM PST this evening for Admiralty
     Inlet-West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 3 AM PST Friday for Central U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 11 PM PST this evening for Puget
     Sound and Hood Canal.

&&

$$

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You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html



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