High Wind in Oregon, February 15, 2017

Area Forecast Discussion
National Weather Service Portland OR
313 PM PST Wed Feb 15 2017

.SYNOPSIS...Low pressure moving past the coast will generate rain
across the region tonight and strong wind coasts for the coast. A
weaker low will move over the area Thursday for showers and possibly
a few thunderstorms. There will be a brief break in rain Friday
morning before another low generates more rain and mountain snow
Friday night and Saturday morning. A broad low over the Northeast
Pacific will continue active weather through much of next week.
&&

.SHORT TERM...Today through Saturday...A cold front is spreading
widespread rain across the area today. Temperatures in the Central
Columbia River Gorge and Upper Hood River Valley are at or just above
freezing early this afternoon, but the lack of reports of ice
accumulation in the area suggest that the road surface temperatures
are too warm to support ice accumulations. Weather observations have
been mostly cold rain.

Satellite imagery shows a surface low near 130W just north of the
Oregon/Washington border. The combination of high pressure over the
Rockies and this low pressure offshore is generating a tight surface
pressure gradient over the coastal waters and an ASCAT pass suggests
there are currently 50 to 55 kt south winds around 30 nm offshore the
central and north Oregon coast. The winds near the coast are still
easterly and may slow the stronger winds from materializing on the
coast, but expect the winds to turn more onshore later this afternoon
or early this evening and become very gusty along the coast. Gusts of
70 to 80 mph are possible for the beaches and headlands and gusts
around 65 mph elsewhere this evening and tonight.

The highest rainfall totals today have been over the North Oregon and
SW Washington coast and coast range where 1 to 1.5 inches have been
observed the past 12 hours. Similar amounts have been observed for
the SW Washington Cascades. Expect an additional 1 to 1.5 inches for
the coast, coast range and SW Washington Cascades tonight through
Thursday afternoon. The rain will be heaviest this evening and
tonight, and turn to showers on Thursday. Small streams and rivers
will rise, especially in the Willapa Hills and North Oregon Coast
range. No rivers are currently expected to flood, but we the  Grays
River at Rosburg shows some potential and we will be monitoring river
levels very closely.

A shortwave trough currently near 38N 137W will move over NW Oregon
and SW Washington Thursday and support convective showers. There has
been quite a bit of lightning with this feature as it developed
offshore today, and expect isolated thunderstorms for the coast as it
nears Thursday morning with isolated thunderstorms possibly inland
Thursday afternoon.

Snow levels are between 9 and 10k feet this morning and will lower to
around 7500 feet late tonight then to around 4500 to 5000 feet as the
showers decrease Thursday afternoon and evening. The Cascade passes
may have 1 to 3 inches of snow Thursday night.

The next low will move south of the area Friday for a brief dry
period Friday morning however showers wrapping around this low will
bring another round of rain and mountain snow Friday night through
Saturday morning. Snow levels will be around 3000 to 4000 feet so
expect additional snow accumulations (1 to 3 inches or so) for the
Cascade passes. ~TJ

.LONG TERM...Saturday night through Wednesday. A rather active
weather pattern continues for the start of next week as a few
impulses will support continued showers Saturday night and Sunday.
While the details in the models remain less than certain, there is
general agreement that a more organized surface low will develop and
move north through the coastal waters somewhere inside of 130W on
Monday, though it remains uncertain at this time just how strong and
how close to the coast it will be. The latest GFS remains a deeper,
faster, and slightly more offshore solution than the ECMWF. As a
result, continued to blend the inherited forecast with both of these
models until confidence in a particular solution increases. Will
need to continue to monitor the model depiction of this low, in
terms of both potential strong winds returning to the coast and also
perhaps a rebuilding of east wind through the Columbia River Gorge.
Forecast models then diverge more by the middle of the week, but it
appears that wet conditions generally remain through the first part
of next week in the form of lowland rain and Cascade snow.   Cullen
&&

.AVIATION...Mix of conditions across forecast area continue this
afternoon as steady rain continues ahead of the next frontal
system. Lower VFR cigs prevail across many terminals, but pockets
of IFR cigs remain in the mid Willamette Valley and along the
Columbia River west of KPDX/KVUO back to KKLS, as well as in the
far western extent of the metro Portland area. Overall a rather
messy set of flying conditions, and expect reduced vsbys and
variable cigs into the evening. Higher terrain will remain
obscured in clouds/rain through the duration of the period.
Strong south winds again arrive at the coastal terminals later
this evening and overnight. Meanwhile, strong east flow through
the gorge will maintain LLWS threat through the afternoon with
stronger low-level S-SW flow.

KPDX AND APPROACHES...Generally low VFR cigs with continuing
light rain. Brief periods of steady heavier rain may bring short
time of low MVFR to IFR cigs/vsbys through the late evening.
East winds persist through the gorge, but speeds drop off quite a
bit between KTTD and KPDX. However, stronger S-SW wind just
above surface continues, so will include LLWS threat through
evening.  Cullen

&&

.MARINE...Had a brief lull in the winds around mid-day near shore.
An ASCAT pass near that same time, however, had a field of 40 kt
winds from about 43-44N and 124-125W. Looks like there was wind
enhancement as the south-southeast winds were accelerated by Cape
Blanco. The next surface low is approaching and winds now starting
to increase again at Buoy 50 with gusts around 43kts. There is not
much change from earlier thoughts other than subtle timing
differences. The storm and associated front looks to bring solid
storm force gusts around 55kt and potential for a brief set of gusts
60-65kt late this afternoon and evening. Still have relatively low
confidence there will be pockets of 64+ kt Hurricane force winds but
will continue to mention the possibility in the CWF and MWW. Winds
will gradually ease overnight behind the front with gusts settling
back down below 21 kt by Thursday mid-morning.

Seas are running 14-16 feet and will increase this evening as the
winds increase. They look to peak around 23 ft as the heart of the
surface low passes by to the west beginning late this afternoon
through this evening from south to north. The combination of fresh
SSW swell at 11 to 12 seconds and long period westerly swell with a
period between 16 and 20 seconds will lead to complex seas for the
next 36 hours.

Have determined the confused sea state will break up enough of the
wave energy such that no single swell direction will carry
significant enough energy to warrant a High Surf Advisory. Do,
however, want to portray that the jetties look to get blasted by
winds and would also expect plenty of waves over-topping them through
the evening, if not into tomorrow.

There will be somewhat of a break as winds and seas gradually
diminish through the early Friday. Another surface low will cross
into northern California Friday afternoon and probably bring some
northerly wind gusts around 25 kt through the night. Another cold
front will sweep from south to north Saturday night. Models then are
waffling about sending a fairly strong and strengthening low across
the waters Monday. /JBonk

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 6 AM PST Thursday for Central Oregon
     Coast.

     High Wind Warning until 6 AM PST Thursday for North Oregon
     Coast.

WA...High Wind Warning from 7 PM this evening to 8 AM PST Thursday
     for South Washington Coast.

PZ...Storm Warning until 1 AM PST Thursday for Waters from Cape
     Shoalwater WA to Florence OR from 10 to 60 nm.

     Small Craft Advisory for Rough Columbia River Bar until 1 PM
     PST Thursday.

     Storm Warning until 1 AM PST Thursday for Coastal Waters from
     Cape Shoalwater WA to Florence OR out 10 nm.

     Gale Warning until 4 PM PST this afternoon for Coastal Waters
     from Cape Shoalwater WA to Florence OR out 10 nm.

&&

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