Flood Watch 2, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
923 AM PST Thu Jan 9 2020

.SYNOPSIS...Scattered showers will taper off through this evening.
A strong frontal system will reach the area Friday, bringing
another round of lowland rain, heavy mountain snow, and windy
conditions to the region. Cold air will move south into the area
starting Sunday night and cold fraser outflow winds are likely
early next week. There will be a chance of snow for the lowlands
of Western Washington from about Sunday night through at least the
middle of next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...Radar currently depicts
scattered showers across the region and have received reports of
some snow and wintry mixes in some spots across the lowlands this
morning. Snow levels remain rather low, ranging from 500-1000 ft,
so could continue to see some snow mix down to the surface, or a
rain/snow mix, in lowland spots through the morning hours.
Precipitation will gradually taper off through this afternoon and
evening.

The next frontal system will affect the region Friday and Friday
night. Could see another wintry mix across the lowlands during the
morning hours, mainly for areas north of Everett. Heavy snow
should fall in the mountains where there is a winter storm watch
in effect. The front should be strong enough for blustery winds.
Good orographics will keep the snow going into the mountains
Saturday-- tapering off later in the day. 14

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...A frontal system will move
through the area Sunday as arctic air settles over British
Columbia and Alberta. The modified arctic front should move south
through Western Washington around Sunday night as cold Fraser
outflow develops up around Bellingham. That will open the door for
the chance of snow through the middle of next week.

&&

.AVIATION...A weak upper level disturbance in NW flow will bring
showers mostly to the interior and Cascades this morning.
Conditions will improve this afternoon. Until then, areas in the
interior will continue to see IFR to MVFR ceilings with mostly VFR
this afternoon. A warm front will spread rain to the coast early
Friday with increasing S wind along the coast and North Interior.
A cold front will keep showers in the region through Friday
afternoon. 33

KSEA...IFR to MVFR cigs this morning with light rain in the
vicinity. Improving conditions this afternoon. Light/variable wind
becoming S 05-10kt this afternoon, then increasing to 15-25 kt by
12z Fri. 33

&&

.MARINE...Gale Watches remain in effect (late tonight into Friday)
as a strong Pacific frontal system moves in. Expect increasing
southerly flow over the waters starting late tonight then easing
Friday afternoon. Strong onshore flow will follow on Saturday.
Meanwhile, seas will be rising as a large swell train reaches the
WA coast (seas building to 20-25 feet on Saturday). Another
vigorous frontal system will bring more high wind on Sunday.
Fraser River outflow winds are expected early next week due to
strong high pressure over interior B.C. This may bring gale force
N/NE winds to the Northern Inland Waters. 33

&&

.HYDROLOGY...Flooding continues on the lower Chehalis and Skokomish
Rivers today. The relative break in widespread precipitation will
allow the rivers to continue to fall into Friday, though Chehalis at
Porter seems to still be slowly rising. Chehalis at Ground and the
Skokomish Rivers will fall below flood stage later today with
Chehalis at Porter cresting today and not falling below flood stage
until Friday night.

The next round of precip coming with the front on Friday will be
rather cold over the Cascades but we still expect a rise on the
Skokomish likely above flood stage again Friday night. There might
be enough precip in the form of rain to raise the threat of
landslides again as well.

Check the latest river forecasts on the AHPS website for details.
Bower

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Watch from late tonight through late Friday night
     for Cascades of Pierce and Lewis Counties-Cascades of
     Snohomish and King Counties-Cascades of Whatcom and Skagit
     Counties-Olympics.

     High Wind Watch from late tonight through Friday afternoon for
     Admiralty Inlet Area-Central Coast-North Coast-San Juan
     County-Western Skagit County-Western Whatcom County.

PZ...Gale Watch from late tonight through Friday 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 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.

     Gale Watch from late tonight through Friday afternoon for
     Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De
     Fuca-Northern Inland Waters Including The San Juan Islands.

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