High Wind in Washington, November 13, 2017

Area Forecast Discussion
National Weather Service Portland OR
904 PM PST Sun Nov 12 2017

.SYNOPSIS...Wet and occasionally windy November weather will prevail
through at least the middle of the upcoming week, as a series of
strong low pressure systems move across the northeast Pacific. These
systems will push strong frontal systems across the Pac NW; the first
of which will move through the region tonight and Monday. This system
will bring strong winds to the coast and to portions of the Coast
Range, and has some potential to bring strong gusts into the inland
valleys as well. Colder air behind this system will drop the snow
levels to the Cascade passes Monday. This system will be replaced by
another over the NE Pacific for more rain, mountain snow, and breezy
conditions over the forecast area later Tuesday through Thursday.
&&

.SHORT TERM...Tonight through Wednesday...The next well advertised
system was taking shape off the coast as a strong low is developing
along 130W. The associated cold front is between 130W and the Oregon
coast and is forecast to move onshore around midnight to 1 AM
tonight/early Monday morning. Lightning has been lighting up along
the front, attesting to its strong and convective nature. When the
front makes landfall, expect a burst of strong winds along the coast,
with high winds possible especially near headlands and beaches, but
possibly even in the coastal communities owing to its convective
nature. This front will then move through the inland areas with a
burst of rain and some breezy winds as it moves east of the Cascades
by sunrise Monday. Behind this front the snow levels in the Cascades
will drop below pass elevations on Monday.

The next feature of interest will be the actual strong low center off
the coast as it moves toward the coast and onshore along the north
Washington coast. A strong gradient associated with the bent back
occlusion around the low center is forecast to move across the north
part of our forecast area Monday afternoon and early evening as the
strong low moves inland to our north. 850 mb winds support gusts on
the north coastal headlands and beaches of at least 70 mph and
possibly close to 80 mph, with 60+ mph in the coastal communities.
The higher elevations of the adjacent coastal mountains could see
gusts up close to 70 mph as well. High wind warnings are in effect
for these areas. It does looking windy in the inland valleys starting
mid morning into the early evening Monday and have issued a Wind
Advisory for these areas as well. The low and bent back occlusion
moves east by mid evening and the winds should then subside some. The
models show some decent precipitation through Monday evening across
the north part of our forecast area from the bent back occlusion, and
we could get decent snow accumulations in the south Washington
Cascades as a result.

The front with the next system starts to move into the area Tuesday
and could produce some heavy rain especially along the coast into
Tuesday night and early Wednesday as is slowly drops south through
the forecast area. We could see some pretty good snows in the
Cascades from this front as well. And it may produce some high wind
along the coast as well. The front may not move south of the area
until late Wednesday or Wednesday evening. Tolleson

.LONG TERM...No Changes. Previous discussion follows...
Wednesday night through Sunday. A trough will maintain breezy
conditions, and showers along the coast and inland areas through the
latter half of the week. An upper ridge will follow during Friday,
and into the weekend. This will bring precip into the area, thanks to
warm air advection. Temps will remain seasonal. Bishop
&&

.AVIATION...A cold front will likely bring a burst of winds, heavier
rain and flight restrictions to the coast around 06-07z and 8-10z for
interior taf sites. A showery and increasingly windy atmosphere
should then bring predominately VFR conditions to the region on
Monday. However, strong south to southwest winds will develop along
the coast between 17-23z with gusts in excess of 50 kt possible,
particularly at KAST. Southerly wind gusts in excess of 30 kt should
also develop in the Willamette Valley during this time.

KPDX AND APPROACHES...A cold front will likely bring a burst of
heavier rain and lower cigs between 08-10z tonight. A windy and
showery airmass will then spread across the region Monday, which
should bring predominantly VFR conditions. Southerly wind gusts of 30
to 40 kt appear likely to develop between 17-23z Monday. /Neuman
&&

.MARINE...A strong low pressure developing well offshore is currently
bring Gale Force wind gusts of 40 to 45 kt to the waters as a cold
front approaches the coastline. A few thunderstorms will be possible
over the waters along this cold front over the next few hours. The
aforementioned winds should result in seas climbing well into the
teens over the next couple of hours, but these seas may back off a
bit as winds temporarily ease behind the front later tonight. As the
main parent low swings back towards the Pacific Northwest late
tonight and Monday morning, pressure gradients will strengthen once
again. This should produce even stronger winds across the waters,
especially across the waters off the north Oregon and south
Washington coast where Storm Force gusts of 50 to 55 kt appear likely
late Monday morning through early Monday afternoon. This should
result in seas climbing above 20 ft across all the waters with 30 ft
not of the question off the Columbia River and south Washington
coast. Seas should be fairly quick to subside Monday evening, though.
However, the next front will drop southeastward and result in Gale
Force wind gusts of 45 kt returning to the waters late Monday night
and Tuesday morning. This should result in seas pushing 20 ft once
again on Tuesday. Winds and seas look to relax Wednesday before a
weak low temporarily increases winds Wednesday night and early
Thursday. The next front looks to arrive over the weekend with
perhaps another round of Gale Force winds possible. /Neuman
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 AM to 7 PM PST Monday for Central
     Willamette Valley-Greater Portland Metro Area-Lower
     Columbia-South Willamette Valley.

     High Wind Warning from 6 AM to 7 PM PST Monday for Coast Range
     of Northwest Oregon.

     High Surf Advisory from 9 AM to 5 PM PST Monday for North
     Oregon Coast.

     High Wind Warning until 4 PM PST Monday for Central Oregon
     Coast.

     High Wind Warning until 6 PM PST Monday for North Oregon Coast.

WA...Winter Weather Advisory from 2 PM Monday to 4 AM PST Tuesday
     for South Washington Cascades.

     Wind Advisory from 7 AM to 7 PM PST Monday for Greater
     Vancouver Area-I-5 Corridor in Cowlitz County.

     High Wind Warning from 6 AM to 7 PM PST Monday for Willapa
     Hills.

     High Surf Advisory from 9 AM to 5 PM PST Monday for South
     Washington Coast.

     High Wind Warning from 8 AM to 6 PM PST Monday for South
     Washington Coast.

PZ...Storm Warning from 4 AM to 4 PM PST Monday for Coastal Waters
     from Cape Shoalwater WA to Cascade Head OR out 60 NM.

     Gale Warning until 4 AM PST Monday for Coastal Waters from Cape
     Shoalwater WA to Cascade Head OR out 60 NM.

     Gale Warning until 6 PM PST Monday for Coastal Waters from
     Cascade Head OR to Florence OR out 60 NM.

     Small Craft Advisory for Rough Columbia River Bar until 6 PM
     PST Monday.

&&

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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the forecast area.