High Wind and Strong Wind in Washington, November 13, 2017

Area Forecast Discussion
National Weather Service Seattle WA
925 PM PST Sun Nov 12 2017

.SYNOPSIS...Rain will continue tonight ahead of a strong frontal
system that will move through the area on Monday. Monday's front
will also be accompanied by strong and gusty winds, especially
along the coast and in the interior north of Everett, and will
bring locally heavy snow to the mountains. The weather will
become somewhat cooler Tuesday through Thursday, with continued
rainy conditions and a snow level around 3000 feet. Wet and
slightly warmer weather is likely Friday and into the weekend.

&&

.SHORT TERM...A strong and strengthening 988 mb low centered near
NOAA Buoy 46005 (46N 131W) is deepening into the center of cold
air aloft. After moving northward and maturing this evening, the
low will turn northeast and slowly fill as it moves into central
or south-central Vancouver Island Monday afternoon. Lightning
detection data continues to show a good deal of lightning over the
offshore waters to the north of the low's occlusion and southward
along the cold front. The lightning would suggest that the low
continues to deepen. Incoming 00Z model solutions are similar to
previous runs and suggest that the current forecast is in very
good shape. Strongest winds are expected along the coast, around
Admiralty Inlet, and near the shorelines of Western Skagit
County, the San Juan Islands, and Western Whatcom County. Most
models keep the winds in the interior from about Snohomish and
Kitsap counties southward below high wind criteria, with gusts in
the 50 to 55 mph range during the afternoon and early evening
hours. Wind gusts in the 4 km UW WRF in the Seattle area appear to
be on the higher side of the envelope of solutions. It appears
that the best coarse of action at this point would be to keep
forecast pretty much where they are.

The low will move inland and weaken Monday night. A surface front
will move across the area Monday morning ahead of the low and
should bring cooler unstable air into the area. Snow levels near
5000 to 5500 feet should fall to around 4000 feet by Monday
afternoon. The amounts of snowfall will depend the amount of flow
and flow direction. There is still a lot of southerly component
which is going to favor heaviest snow amounts above the passes
along south facing slopes including spots like Mount Baker and
Paradise Ranger Station at Mt Rainier Natl Park. However, higher
passes like Stevens and White pass could get 6+ inches, especially
Monday evening. A winter weather advisory was issued although
snow amounts and timing are fairly uncertain. Call 5- 1-1 ahead of
time for pass conditions before departing.

Rain will also fall across the lowlands and some river basins.
Amounts do not appear enough to cause river flooding except on the
Skokomish River in Mason County. See latest flood statements for
further information.

Another wet front will arrive on Tuesday and slowly push southeast
through the area Tuesday night or Wednesday morning. Expect
another period of breezy to windy conditions and locally heavy
rainfall. Snow levels might not rise very much and significant
snowfall could develop in the mountains. A cool and showery
pattern is likely by Wednesday as the main upper low approaches
the region.  Albrecht/Mercer

.LONG TERM...From the previous long term discussion: Cool and
showery conditions look to continue into Thursday. Thereafter, the
pattern becomes much more uncertain. Most models still show
fronts affecting the area with rain at times. There is still a
possible atmospheric river event to watch for. The GFS still shows
higher upper heights with a milder air mass and tap of moisture
well out into the Pacific. The ECMWF is much progressive overall
with the pattern and would indicate no flood threat. Expect wet
and unsettled weather next weekend but no certainty as to
potential rain amounts at this point. Mercer

&&

.AVIATION...A vigorous upper trough will cross Western Washington
on Monday, and a fairly deep surface low will move onshore central
Vancouver Island Monday afternoon. Strong southwest flow aloft
through Tuesday, becoming moderate on Tuesday night. The air mass
will be moist and a little unstable. An easterly component to
low-level wind flow will inhibit clouds below 030 until Monday
afternoon, then cigs should lower with a turn to low-level onshore
flow on Monday evening. Strong surface winds will be a big
aviation issue, with low-level wind shear possible through Monday
morning, especially where easterly surface wind interacts with the
strong southwest flow aloft.

KSEA...Low-level wind shear will be increasing tonight, given
easterly surface wind and increasing southwest flow aloft. LLWS
concerns should ease after 12z-14z, when surface wind should
become more southerly. Then the main concern on Monday will be
strong surface wind. Sfc wind will peak on Monday afternoon
between 21z-02z (1 pm-6 pm), with peak southerly gusts around
38-44 kt. Otherwise, cigs will generally hold AOA 050 through
Monday morning, then lower below 030 over the course of Monday
afternoon. Rain at times is a given.  Haner

&&

.MARINE...A 984 mb low near 46N 132W this evening will move
to central Vancouver Island on Monday afternoon, bringing very
strong southeast gradients through Monday afternoon along with
Storm-force winds in southeast wind-prone waters. A brief but
strong onshore turn is expected on Monday evening. A slow-moving
cold front will approach the coast on Tuesday, preceded by strong
southeast gradients. Haner

&&

.HYDROLOGY...The Skokomish River will go above flood stage late
this evening and may stay above flood stage at Potlatch for the
next couple of days.

Elsewhere, rain will be heavy at times tonight and Monday as a
low moves into the region. However, pattern is not favorable for
flooding on other area rivers.

For Tuesday through Wednesday, flow aloft will be southwesterly
and snow levels will be below about 5000 feet. Other than the
Skokomish, river flooding is not expected.

There has been some concern of an atmospheric river set up next
weekend for the past few days. However, long range forecast models
are quite inconsistent from Thursday onward. Overall, the flood
threat is less today than it was earlier in the weekend, but
flooding next weekend cannot be ruled out yet. Forecasts should
be monitored.  Albrecht/Mercer

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 7 AM to 7 PM PST Monday for Bellevue and
     Vicinity-Bremerton and Vicinity-East Puget Sound Lowlands-
     Eastern Strait of Juan de Fuca-Everett and Vicinity-Hood
     Canal Area-Lower Chehalis Valley Area-Seattle and Vicinity-
     Southwest Interior-Tacoma Area.

     Winter Weather Advisory from 4 AM Monday to 4 AM PST Tuesday for
     Cascades of Pierce and Lewis Counties-Cascades of Snohomish
     and King Counties-Cascades of Whatcom and Skagit Counties-
     Olympics.

     Flood Watch from midnight PST tonight through Wednesday morning
     for Hood Canal Area-Lower Chehalis Valley Area-Olympics.

     High Wind Warning from 6 AM to 6 PM PST Monday for Admiralty
     Inlet Area-San Juan County-Western Skagit County-Western
     Whatcom County.

     High Wind Warning from 3 AM to 3 PM PST Monday for Central Coast-
     North Coast.

     High Surf Advisory from 7 AM to 9 PM PST Monday for Central
     Coast-North Coast.

PZ...Small Craft Advisory for rough bar from 3 AM Monday to 6 AM PST
     Tuesday for Grays Harbor Bar.

     Storm Warning until 6 PM PST Monday 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-East Entrance U.S. Waters Strait Of Juan De Fuca-
     Northern Inland Waters Including The San Juan Islands.

     Gale Warning until 7 PM PST Monday for West Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Gale Warning until 10 PM PST Monday for Central U.S. Waters
     Strait Of Juan De Fuca.

     Gale Warning until 6 PM PST Monday for Admiralty Inlet.

     Gale Warning until 9 PM PST Monday for Puget Sound and Hood
     Canal.

&&

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html