High Wind in Oregon, January 21, 2018

Area Forecast Discussion
National Weather Service Portland OR
251 AM PST Sun Jan 21 2018

.SYNOPSIS...Low pressure developing off the Pac NW coast will push a
strong cold front across the forecast area today, bringing strong
winds and high surf to the coast this morning, with rain and Cascades
snow throughout the day inland. A cool, showery pattern will linger
through Monday, then another strong frontal system is expected
Tuesday. Tuesday's front is expected to stall over the area, with
rain and mountain snow likely to persist into Wednesday. Following
more showers Thursday from the associated trailing upper trough,
another decent and possibly wet frontal system is expected next
weekend.

&&

.SHORT TERM...Today through Tuesday...Latest observations show the
wind is beginning to ramp up along the coast, with gusts to 57 mph
already being reported at Cape Disappointment. Winds will continue to
increase as a strong Pacific frontal system nears the coast, moving
onshore between 8 AM and 11 AM this morning. We have been watching
the portion of the front near 45N/130W closely the past couple hours,
as there have been signs of cyclogenesis there. However, the lack of
lightning strikes in the area seems to indicate that the low is not
developing much faster than models suggest. Therefore, the current
forecast of gusts to 65 mph for the beaches and headlands looks to be
in good shape. Will make no changes to the High Wind Warning, though
it will probably be able to be cancelled a little earlier than 1 PM,
especially for our northern coastal zones. There will probably be a
brief spike in winds inland today as the front moves through, but
gusts should generally remain below 40 mph for the valleys.

This front will spread steady light to moderate rain onshore and
across the forecast area this morning, falling as snow in the
Cascades above around 3000-3500 feet. This system will be occluding
as it moves onshore, so there probably won't be much of a jump in
snow level ahead of the front. NAM Bufr soundings suggest Hood River
and Eastern Skamania Counties will probably start off with a bit
lower of a snow level this morning; perhaps around 1000-1500 feet
before snow levels jump to where they are for the rest of the
Cascades as the front moves through this afternoon. Accumulations
will probably be modest in the Upper Hood River Valley; perhaps 1 to
locally 2-3 inches of snow...which is below advisory criteria. QPF
still looks to be enough to warrant a low-end Winter Weather Advisory
for the Cascades, with 4-8 inches of snow expected to be common.

Another round of southwesterly onshore flow will bring more showers
to the forecast area tonight and Monday, with some shadowing in
the valleys at times, but with reduced QPF totals as compared to
what is expected on today. A couple thunderstorms are possible along
the S WA/far N OR coast tonight as the upper cold pool swings across
the area.

Things will start to dry out Monday night as we are in between
systems, but another decent Pacific front is expected to spread in
Tuesday with more rain, Cascade snow, and some wind along the coast.
Models finally seem to be coming together on how to handle this front
and associated low pressure system, developing a fairly strong low
well offshore and tracking it into British Columbia. This will push a
decent front onshore Tuesday, with weak waves of low pressure riding
N-NE along the front. With cool air left behind by today's system,
this system may dump a decent amount of snow in the Cascades,
especially Mount Hood northward. Easterly flow through the Gorge
ahead of this system will probably result in low snow levels in the
Hood River Valley and eastern Skamania County, and significant
accumulations are possible depending on how long it takes for this
system to scour out cool air east of the Cascades. The air east of
the Cascades does not look cold enough to cause significant problems
in the Columbia Gorge.	Weagle

.LONG TERM...No Changes. Previous discussion follows...
Tuesday night through Saturday...Active weather to continue through
the extended forecast period with little-to-no break in the
precipitation.	A slow-moving upper-level trough will keep moisture
pushing into the Pacific Northwest, with low pressure systems
generally riding along a track from the southwest up into northern
Washington or British Columbia.  With this pattern, expect
coast/valley rain and mountain snow. Snow levels could fall down to
around 1500 ft behind the front moving through Wednesday night and
Thursday, but still wouldn't anticipate any significant snow below
2000 ft as showers will be dwindling. Saturday, there appears to be
another mild and wet system moving in, bringing snow levels back up
for the weekend. -McCoy

&&

.AVIATION...A strong cold front will move to the coast this
morning between 16Z north coast and 19Z for the central Oregon
coast, the through the interior lowlands 20-23Z. Strong winds
gusting 40 to 50 kt at the coast until frontal passage. Inland
areas may see 20 to 30 kt gusts with the front. Winds ease behind
the front. Expect mainly VFR conditions becoming MVFR cigs and
visibility as the front moves through. There is a slight chance
of thunderstorms in the vicinity of KAST this evening.

PDX AND APPROACHES...VFR prevailing with MVFR becoming likely
with 20-23Z Sun as a front moves through. Expect VFR to prevail
this evening and overnight.  Easterly wind 10 to 15 kt will
switch to south 15 kt gusting 25 kt between 20 and 23Z then ease.
/26

&&

.MARINE...Solid gales as of 2 am with peak wind gusts around 40
to 45 kt. Model indications 40 to 50 kt gusts still expected
through about 10 am. The waters south of Cascade Head will have
gale to storm force winds a few hours longer so have extended the
Storm Warning there.  Seas are ramping up, mainly due to wind
driven waves and fresh swell. Will probably have seas 19-23 ft
peaking between 8 am and noon today. Seas will be slow to fall,
remaining above 15 feet through Monday morning.

Active weather remains with us through the week with fronts
coming through every 48 hours or so. There is still some
uncertainty on the timing and strength of these fronts, but each
of them brings the possibility of gale force winds and seas
approaching 20 feet. The next gale currently forecast for Tue-Tue
night. /mh

With the expected large waves today will issue a High Surf
Advisory for the south Washington, north and central Oregon
coasts. Fortunately the peak wave heights will be during low tide
this morning. But venturing out on the jetties and near the surf
zone will still be dangerous. Large wave will subside this
afternoon and evening.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 1 PM PST this afternoon for Central
     Oregon Coast-North Oregon Coast.

     High Surf Advisory until 1 PM PST this afternoon for Central
     Oregon Coast-North Oregon Coast.

     Winter Weather Advisory until 6 PM PST this evening for
     Cascades in Lane County-Northern Oregon Cascades.

WA...High Wind Warning until 1 PM PST this afternoon for South
     Washington Coast.

     High Surf Advisory until 1 PM PST this afternoon for South
     Washington Coast.

     Winter Weather Advisory until 6 PM PST this evening for South
     Washington Cascades.

PZ...Storm Warning until 10 AM PST this morning for Coastal Waters
     from Cape Shoalwater WA to Cascade Head OR out 60 NM.

     Storm Warning until 1 PM PST this afternoon for Coastal Waters
     from Cascade Head OR to Florence OR out 60 NM.

     Small Craft Advisory for Rough Columbia River Bar until 4 AM
     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 CWA or forecast area.