High Wind and Strong Wind in Oregon, October 15, 2016

Area Forecast Discussion
National Weather Service Portland Oregon
325 AM PDT Sat Oct 15 2016

.SYNOPSIS...Am intense low pres system will move north off the
Oregon and WA coast today, passing near the nw tip of the Olympic
peninsula at the end of the day, bringing strong winds, heavy rain
and high seas to the Pacific NW. A couple of weaker troughs of low
pres Sun through Mon night will keep the weather active into early
next week.

&&

.SHORT TERM...(Saturday through Monday)...Nose of a 160 kt jet was
crossing 140w at 40n early this morning, expected to energize a
surface low near 40n 135w. Models have come into reasonable
agreement on track and intensity of the low as it curves north today
and move up off the Oregon and WA coast. The 00z GFS is tending
toward a weaker solution with central pres down to 980 mb, while the
00z EC and 06z Nam continue to suggest central pres down to around
970 mb. Prefer to go with the deeper lows of the Nam and EC due to
consistency, yielding a best guess for the storm to pass about 80 nm
off the coast of Astoria midday, with pres bottoming out near 970 mb
shortly thereafter. While not a Columbus Day storm repeat by any
means as model 850 mb winds appear capped around 70 to 80 kt, it
still looks like a substantial storm, esp for the coast. Will keep
peak gusts at low elevations on the coast around 80 mph, while
Willamette Valley can expect peak gusts to fall in the range of 50
to 60 mph in the north, lower further south. Seas on the coast
expected to peak around 30 ft late today, resulting in a high surf
warning for the coast. With peak seas expected to follow high tides
by 2 to 6 hours, the timing suggests coastal flooding is unlikely to
be a significant issue. While the 850 mb wind field remains strong
along the coast with this system, precipitable water is expected to
peak just over one inch along the coast and in the coast range
suggesting rainfall potential is not quite as strong as the Thu to
Fri storms.

Once the associated cold front pushes inland at the end of the day,
precipitation expected to become more showery. Broad cyclonic flow
continues Sun and Mon over the east Pacific, keeping a moist onshore
flow going through Mon for continued showery weather with high pops.
A surface torugh of low pres expected to push move inland Sun night
will return gusty winds to the coast as well as the inland valleys,
but gradients do not appear strong enough to bring high winds.

.LONG TERM...(Monday night through Thursday)...No changes. Previous
discussion follows. Models begin to diverge some with timing of lows
moving toward the coast. This is due the the difficulty the models
having in picking up on tropical moisture from the western Pacific
being injected into the westerlies. GFS has been consistently
showing a 1000mb low moving onto the Washington coast Tuesday with
the ECMWF having a much slower solution bringing this system over a
developing weak ridge on Tuesday night with rain brushing Northwest
Oregon. Both the ECMWF and GFS build the ridge Wednesday and
Thursday pushing the storm track mostly into Washington. I have
lowered the chance of precipitation some for Wednesday night and
Thursday, but will still leave a chance or slight chance of rain in
the forecast due to the uncertainty in the models.     Schneider

&&

.AVIATION...Mostly VFR conditions early this morning with some
isolated IFR and MVFR generally in showers. Thunderstorms should
be done. Rain is currently becoming steadier from south to north as
a warm front approaches. Expect conditions to gradually become
MVFR along with that rain. A very strong low will move up from
the south during the day today, passing just off the Oregon and
Washington coast. This will bring rapidly increasing southerly
winds from south to north during the late morning, with high winds
continuing into the evening. The coastal TAF sites can expect
gusts in excess of 50 kt. The northern interior TAF sites will
likely see gusts of 40 kt to 50 kt with gusts to around 40 kt
farther south. Conditions should become primarily VFR as the
winds begin to pick up during the day Sat.

KPDX AND APPROACHES...Expect mainly VFR conditions in showers
into this morning. Brief periods of MVFR are possible in heavier
showers. Rain becomes steadier this morning, with conditions
becoming predominantly MVFR by around 14Z. Strong winds will
impact the terminal this afternoon and evening. They will start
out as breezy out of the east, then switch to strong and out of
the south by mid afternoon. There is potential for southerly wind
gusts as high as about 50 kt. Conditions should become VFR as
winds pick up Sat. Bowen/Pyle

&&

.MARINE...Biggest change early this morning was to upgrade to a
Hurricane Force Wind Warning for all of the waters, starting south
mid morning through late afternoon today and extending north
starting late morning through this evening. With models in good
agreement, am fairly confident that gusts will peak at 65 kt to 70
kt, although winds may not be fully captured by the few local
buoy reports we have.

Seas bottomed out around 15 ft around midnight and are slowly on
their way back up, with 16 to 17 ft currently at buoys 50 and 29.
Expect seas to jump above 20 ft by mid morning then peak around 30
ft this afternoon and evening.

Another weaker low may come in Sun with wind gust around 30 to 35
kt. However, the forecast generally trends toward more benign
conditions as we get into next week. Bowen/Pyle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 11 AM this morning to 9 PM PDT this
     evening for Central Willamette Valley-Greater Portland
     Metro Area-Northern Oregon Cascade Foothills.

     High Wind Warning from 2 PM this afternoon to midnight PDT
     tonight for Lower Columbia.

     High Wind Warning from 8 AM this morning to 5 PM PDT this
     afternoon for Central Coast Range of Western Oregon-
     Central Oregon Coast.

     High Surf Warning from noon today to 10 PM PDT this evening for
     Central Oregon Coast-North Oregon Coast.

     Wind Advisory from 8 AM this morning to 5 PM PDT this afternoon
     for South Willamette Valley.

     High Wind Warning from 11 AM this morning to midnight PDT
     tonight for Coast Range of Northwest Oregon-North Oregon
     Coast.

WA...High Wind Warning from 11 AM this morning to 9 PM PDT this
     evening for Greater Vancouver Area.

     High Wind Warning from 2 PM this afternoon to midnight PDT
     tonight for I-5 Corridor in Cowlitz County-South
     Washington Cascade Foothills-South Washington Coast-
     Willapa Hills.

     High Surf Warning from noon today to 10 PM PDT this evening for
     South Washington Coast.

     Coastal Flood Advisory from 9 AM this morning to 2 PM PDT this
     afternoon for South Washington Coast.

PZ...Small Craft Advisory until 5 AM PDT early this morning for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     60 nm.

     Hurricane Force Wind Warning from 11 AM this morning to 8 PM
     PDT this evening for Coastal Waters from Cape Shoalwater
     WA to Cascade Head OR out 60 nm.

     Gale Warning from 7 AM to 11 AM PDT this morning for Coastal
     Waters from Cape Shoalwater WA to Cascade Head OR out 60
     nm.

     Hurricane Force Wind Warning from 9 AM this morning to 5 PM PDT
     this afternoon for Coastal Waters from Cascade Head OR to
     Florence OR out 60 nm.

     Gale Warning until 9 AM PDT this morning for Coastal Waters
     from Cascade Head OR to Florence OR out 60 nm.

     Small Craft Advisory for Rough Columbia River Bar until 5 AM
     PDT Sunday.

&&

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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.