High Wind in Oregon, November 14, 2020

Area Forecast Discussion
National Weather Service Portland OR
212 PM PST Sat Nov 14 2020

.SYNOPSIS...Welcome to November, loaded with clouds, rain and
mountain snow, and even some wind at times. Front approaching the
region this afternoon will push inland later tonight. This maintains
wet and breezy afternoon and evening. Showers on tap for Sunday, but
rain spreads across region again Sunday night into Monday. Mild day
on Monday, with break in the weather for the afternoon and overnight
hours. But, another strong front will push into region on Tuesday.
Unsettled weather continue through Friday.

&&

.SHORT TERM...Tonight through Tuesday...NOAA satellite imagery
showing rather impressive low over the southeast Gulf of Alaska this
afternoon, with a frontal system extending southward towards
Vancouver Island and back offshore from the Pac NW. Warm front
offshore as of 2 pm will maintain rain across the region. But,
trailing cold front is not too far behind, and will push to the coast
by 7 or 8 pm, then push inland overnight.

This front will bring wind, rain and snow to the region this
afternoon and tonight. Winds will continue to pick up as cold front
approaches. While not expected winds as strong as those seen this
past Thu night, will see gusty south winds along the coast, with the
strongest south of Lincoln City. Low level dynamics with 925 mb flow
suggests 45 to 55 mph winds for the coastal areas, with strongest on
headlands and open beaches. Based on current models, looks like the
triple point will shift inland along the north Oregon coast,
somewhere near Tillamook. So, with that in mind, will see a brief
period of stronger gusts to the south of Tillamook. Best guess is
that will have brief period of stronger gusts 55 to 65 mph, with
strongest on exposed areas such as headlands and beaches and higher
bridges. Timewise, generally this being from 4 pm to 7 pm, and to
from Lincoln City southward. Winds will ease after 8 pm. Will
maintain current High Wind Warning for the coast of West Central
Oregon through 7 pm today. Will be breezy inland as well, but gusts
mostly in 20 to 30 mph range.

Decent rainfall along the coast as well as the Coast Mtns and Willapa
Hills. Generally, heaviest rainfall for this area will be this
afternoon into the evening. Modeled integrated moisture transport
continues to show potential of 2 to 4 inches of rain over those
areas. At moment, would not expect any river flooding. But, Grays
River may have to be monitored, as will see sharp rises on it again
later today into the evening. But, front will move through the region
fairly quickly, curtailing the heaviest rainfall. So, while not
expecting any flooding, but the river level will rise quite a bit.
Rest of the region will maintain another wet afternoon/evening, with
0.75 to 1.50 inches of rain for interior lowlands, including the I5
corridor. As such, likely will see spotty ponding of water in areas
with poor drainage, such as underpasses, low spots in rural roads, as
well as some leaf-covered storm drains overnight.

Snow levels will vary considerably, both spatially and temporally,
during the next 24-36 hours. Snow levels around 3500 feet this
afternoon, but will rise quickly to 5000 feet this evening. The one
exception to this will likely be eastern portions of Skamania County
and the Hood River Valley, where low-level cold air will take a while
to scour out. Will maintain current Winter Weather Warning for the
south Washington Cascades. But, not convinced will see all that much
for the north Oregon Cascades, though heaviest snowfall likely to be
higher up on Mount Hood. So, will change Winter Storm Warning for the
north Oregon Cascades over to a Winter Weather Advisory, with 4 to 9
inches. Farther to the south, Santiam and Willamette
Passes will see 1 to 5 inches of snow into this evening before snow
levels jump above those elevations.

Frontal boundary shifts inland later tonight, with rain turning to
showers after midnight. Still showery for Sunday, though will have
some rather large breaks between showers. But, the front somewhat
hung up over the Cascades back across southwest Oregon during the
day, with more steady showers or rain for those areas.

Models now showing the front lifting back north as a warm front
Sunday night, with rain spreading northward overnight. Will boost
PoPs and change grids to reflect this. Would not expect heavy rain,
but mostly 0.25 to 0.50 inch of rain for Sunday night into Monday
morning. This warm front will lift north quickly Monday morning, with
rain well north of the Columbia River by mid to late afternoon. Still
decent amount of clouds across region. But, with no rain and some
breaks in the cloud cover, seems reasonable to get afternoon
temperatures into the upper 50s to lower 60s, especially for areas
south of Salem. Dry weather on tap for Monday night. But, with high
pressure east of the Cascades, and deepening low pressure well
offshore, will see increasing easterly winds.

Next system arriving Tuesday, with rain spreading inland early in the
day. But, some uncertainty with this system. At moment, models
trending with rather strong low offshore that will lift
north-northeast towards Vancouver Island during the day. With that in
mind, will likely stay on lighter precipitation side for most of the
day, along with somewhat breezy east to southeasterly winds. But, if
low track more eastward, then could easily get into more rain and
better potential for breezy south winds. Either way, looks to be
another wet day for the region. Another concern will be the potential
for tidal overflow along the south Washington coast on Tuesday
afternoon. Given uncertainty of wind speeds and seas, will have to
watch this as draw closer.			   /Rockey

.LONG TERM...Tuesday night through Friday...Cluster analysis shows a
high probability that the region will continue to be on the leading
edge of a deep upper level trough Tuesday night. The deep upper level
low
will shift north and dissipate by Wednesday night. The surface low
will continue to strengthen Tuesday as it moves northeast towards
Haida Gwaii. By Tuesday evening surface winds will likely shift
onshore bringing stratiform rain within the warm front across the
region. Gusty southerly winds are expected Tuesday night as gradients
tighten within the warm front. NBM shows a 40% chance that KPDX will
see wind gusts up to 35 kt, wind gusts will likely stay between 20
to 25 kt. These stronger gusts are possible if this low continues to
strengthen like the models are depicting at this time.

The 12Z GFS and NAM both show a weak shortwave ahead of the cold
front which will likely support another rise in QPF Wednesday
afternoon. Cold front will likely push onshore Wednesday night
bringing showers across the area into Friday. Potential for a
transitional period Friday as a transient upper level ridge moves
across the Pacific NW. Weak surface ridging is likely to build
Friday night which could bring a brief pause in the rain. But, as
this is so far out confidence is low.		  /BPhillips

&&

.AVIATION...Warm-frontal precipitation continues to spread over
the area early this afternoon. Primarily VFR at 21Z, but MVFR
coverage has gradually increased since this morning. Flight
conditions to gradually deteriorate through the remainder of the
afternoon and into the evening, with widespread MVFR conditions
by 00Z Sun. The heaviest precipitation is expected to occur late
this afternoon through around 06Z Sun, which will result in
areas of IFR vis and/or cigs. Improvement to VFR occurs over the
south Washington and north Oregon coastal areas overnight. VFR
conditions over the interior lowlands not likely until at least
12Z Sun. Conditions after 18Z Sun should be primarily VFR, with
areas of MVFR over the Cascades and foothills.

Increasing south wind develops over the south half of the forecast
area late this afternoon and eventually spreads north by early
evening. The strongest wind speeds will be along the central
coast, including KONP, where a few hours of gusts 40-50 kt are
expected late this afternoon and very early this evening.
Elsewhere, gusts will generally peak in the 25-30 kt range. Wind
speeds rapidly diminish late this evening.

For detailed regional Pac NW weather information, go online to:
http://weather.gov/zse

KPDX AND APPROACHES...Warm-frontal light precipitation at 21Z
has resulted in occasional MVFR cigs at the terminal. A mix of
MVFR and VFR will continue through 00Z Sun and then settle into
predominant MVFR thereafter. Return to VFR not likely until early
Sun morning. Heaviest precipitation expected to occur from 00Z
Sun to 06Z Sun, with vis possibly lowering to 3sm. IFR to become
more prevalent in the Tualatin River Valley 00Z to 08Z Sun. Have
indicated LLWS for KTTD through the evening with east surface
wind and 35-40 kt south wind at FL020. Weishaar

&&

.MARINE...The 12Z model runs are in good agreement regarding the
strength and location of the approaching low pressure. In fact,
the 12Z ECMWF MSLP ensembles are in excellent agreement, showing
a 970 mb surface low slightly northwest of Vancouver Island at
06Z Sun. The only model differences from 24 hours ago are slightly
lower boundary layer wind speeds late this afternoon into early
evening and a little more northward extension of coastal jet
potential. High confidence in achieving storm force wind gusts
over the central waters, especially from near shore to 30-40 nm
west. A little less confidence in storm force gusts for the
northern waters, especially north of Cape Falcon. Models maintain
some degree of easterly component north of Cape Falcon through
early evening.

Wind speeds rapidly diminish late this evening into Sun morning,
likely falling below small craft advisory thresholds over PZZ255
and PZZ275. Gusts to 25 kt will continue over the north zones
into Sun afternoon. Models are in good agreement that a fairly
strong warm front moves north through the waters Sun night into
Mon morning. Model solutions continue to vary quite a bit with
this system. The 12Z ECMWF MSLP individual ensemble members show
even more variability with surface low placement valid 06Z Tue
compared to the previous run. The 12Z deterministic models also
exhibit differences, especially with the orientation of the
surface low and central pressure. The low is forecast to remain
just outside 130W Mon night into Tue morning, resulting in
offshore low-level flow. Gale force wind speeds during this time
will remain over the outer waters, generally beyond 25nm. Would
tend to discount the NAM solution at this time due to the smaller
model domain and with the low developing near or outside the
model boundary. The deterministic GFS and ECMWF provide somewhat
similar solutions showing the low racing to the British Columbia
coast just north of Vancouver Island around 00Z Wed. Moderate
confidence exists to go with gale force gusts returning to PZZ255
and PZZ275 early Mon afternoon and spreading to the north zones
mid to late afternoon. There is also the possibility of storm
force gusts over the outer waters Mon evening, but forecast
confidence is a little lower. Longer range guidance shows a much
quieter pattern developing for the latter half of next week.

Expect a generally confused sea state through this evening due
to the large wind-wave component, building to 10-15 ft during the
storm force period. This large wind wave added to the existing
11-13 ft northwest swell will produce waves near 20 ft. Seas come
down fairly quickly Sun night into Mon but continue to wildly
fluctuate for the waters with each passing model run and between
individual models. At a minimum, expect seas to hover in the mid
to upper teens through Sun morning and then build to near 20 ft
Sun afternoon. Seas subside Sun night through Mon, lowering to
10-13 ft Mon afternoon. Wave models continue to struggle with
forecast wave heights Tue. The 13/12Z spectral analysis guidance
suggested seas to near 30 ft at buoy 46029 Tue. The 14/12Z run
shows peak wave heights near 20 ft, a substantial change from 24
hours ago. The 12Z ENP and ECMWF wave model show wave heights
near 20 ft Tue afternoon, but dominated by a southwest swell. The
NBM is slightly lower showing upper teens. Would tend to favor
the slightly lower values based on the expected offshore low-
level flow. Seas eventually fall below 10 ft toward the end of
next week.				    / Weishaar

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 9 PM PST this evening for Upper
     Hood River Valley.

     High Wind Warning until 7 PM PST this evening for Central
     Oregon Coast.

     Winter Weather Advisory until 2 AM PST Sunday for Northern
     Oregon Cascades.

WA...Winter Storm Warning until 2 AM PST Sunday for South Washington
     Cascades.

PZ...Storm Warning until 7 PM PST this evening for coastal waters
     from Cape Shoalwater WA to Cascade Head OR out 60 NM.

     Gale Warning until 3 PM PST this afternoon for coastal waters
     from Cape Shoalwater WA to Cascade Head OR out 60 NM.

     Storm Warning until 7 PM PST this evening for coastal waters
     from Cascade Head OR to Florence OR out 60 NM.

     Small Craft Advisory until 4 PM PST Sunday for Columbia River
     Bar.

&&

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 3 PM this afternoon to 9 PM PST
     this evening for Upper Hood River Valley.

     High Wind Warning from 1 PM this afternoon to 7 PM PST this
     evening for Central Oregon Coast.

     Winter Storm Warning until 2 AM PST Sunday for Northern Oregon
     Cascades.

WA...Winter Storm Warning until 2 AM PST Sunday for South Washington
     Cascades.

PZ...Storm Warning from 3 PM this afternoon to 7 PM PST this evening
     for coastal waters from Cape Shoalwater WA to Cascade Head
     OR out 60 NM.

     Gale Warning until 3 PM PST this afternoon for coastal waters
     from Cape Shoalwater WA to Cascade Head OR out 60 NM.

     Storm Warning from 1 PM this afternoon to 7 PM PST this evening
     for coastal waters from Cascade Head OR to Florence OR out
     60 NM.

     Gale Warning until 1 PM PST this afternoon for coastal waters
     from Cascade Head OR to Florence OR out 60 NM.

     Small Craft Advisory until 4 PM PST Sunday for Columbia River
     Bar.

&&

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