High Wind and Strong Wind in Oregon, March 12, 2022

Area Forecast Discussion
National Weather Service Portland OR
944 AM PST Sat Mar 12 2022

Updated aviation and headlines, added beach hazards section

.SYNOPSIS...The first in a series of low pressure systems will
begin to impact the area this afternoon with rain, coastal wind,
and mountain snow persisting through the weekend. There is the
potential for high wind along the Oregon beaches and headlands
through early Sunday morning. A weak atmospheric river pattern
is expected on Monday. The unsettled pattern then continues
through late in the week.

&&

.SHORT TERM...THROUGH MONDAY NIGHT...The upper level ridge axis
has shifted east of the Cascades this morning, opening the door
to moist onshore flow and increasing cloud cover ahead of a
developing system presently located well offshore near 45N 135W.
This system will bring about the much anticipated pattern
change to rainier weather later today as a strong cold front
moves through the coastal waters and onto the coast. Rain should
reach the coast around late morning and then spread inland
through the afternoon. The front will also be accompanied by a
period of strong southerly winds this afternoon. A High Wind
Warning remains in effect for the beaches and headlands on the
OR Coast, where widespread 50-60 mph gusts are expected during
the afternoon. The rapidly deepening surface low associated with
the front will reach peak intensity in the low to mid 980 mb
range late this afternoon approximately 350 miles offshore, then
race towards the south WA Coast tonight. This will allow a
bent-back occlusion to take aim on the OR Coast and bring
another round of heavier rain and strong winds to the area
overnight into Sunday morning. Winds will this time be from more
of a west-southwest direction, and could also bring breezy
conditions to the Willamette Valley overnight. Holding gusts
below advisory level for now in the valley, but it isn't out of
the question that winds could gust as high as 45 mph in a few
locations tonight. In terms of rainfall totals, expect over an
inch in most locations through Sunday morning, with parts of the
Coast Range seeing upwards of 2 inches. Meanwhile, valley
locations are expected to see anywhere from a half to one inch
of rain through Sunday morning. Snow levels will start out
around 4500 feet today but will fall to 3000 feet through Sunday
morning, with locally heavy snow totaling as much as 12 to 18
inches in the Cascade passes and ski areas through Sunday
afternoon. The winter weather advisory remains in place through
Sunday afternoon above 3000 feet.

Sunday afternoon into Sunday night will bring a relative lull in
precipitation between systems but will remain showery through early
Monday ahead of the next system to impact the region. Another front
looks to arrive along the coast sometime Monday afternoon,
accompanied by another period of strong southerly winds at the
coast. Guidance continues to suggest that this will be the wetter of
the two systems, with indicators pointing to a weak atmospheric
river event as IVT values surpass 500 along the central and northern
OR Coast through Monday evening. Not expecting widespread hydro
issues since the system will move through relatively quickly, but
more responsive coastal rivers such as the Grays in SW WA will have
to be monitored closely in the coming days. /CB

.LONG TERM...TUESDAY THROUGH FRIDAY...The overall pattern become
a little less active beyond Tuesday. The WPC 500 mb clusters
are in general agreement showing some degree of ridging centered
along the coastline Wednesday. Close to 50 percent of the EPS
members indicate a slightly stronger ridge centered near 125W,
while a little more than half of the GEFS members show weaker
ridging. All in all, am not completely confident in a totally
dry forecast in the Wednesday through Friday time frame.
Weishaar

&&

.AVIATION...18Z TAFs: Current conditions across the area show VFR
with clear skies for inland sites with conditions beginning to
deteriorate at the coast as a strong low offshore pushes east.
Heavy rain with reduced visibility is likely along the coast
strong southerly winds in the 35-40 kt range. The front will move
inland around 03Z Sunday bringing gusty conditions and heavy rain
across
the interior. Wind gusts up to 35 kt possible across the central
Willamette Valley around 12Z Sunday.

Once the initial band of rain passes, the pattern will turn more
showery with a low VFR/high MVFR broken ceiling inland and a low
MVFR ceiling along the coast. Deterioration of conditions into
the IFR category is possible in any heavy showers, especially
along the coast where HREF guidance is suggesting probabilities of
IFR ceilings as high as 70% with showers. Also, some shadowing
may occur amidst the west-southwesterly flow Saturday night into
Sunday in the western Willamette Valley which could allow for some
patchy fog to develop within cloud breaks between passing
showers.

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

KPDX AND APPROACHES...VFR ceilings and visibility are expected to
continue throughout the TAF period. There will be a lowering of
ceilings with frontal approach with heavy rain and MVFR conditions
possible for a period. Behind it, a broken low VFR or high MVFR cloud
deck is likely. Gusty winds possible with showers Saturday afternoon
through the end of the TAF period, and a more sustained period of
30-35 kt wind gusts is possible from 06z to 12z Sunday.
-BMuhlestein/Bumgardner

&&

.MARINE...The calm before the storm is slowly coming to an end as
southerly winds increase into the Small Craft Advisory range. Winds
will increase fairly quickly this morning into the early afternoon,
and should peak in a line moving southwest to northeast across the
waters from around 11 AM in the outer central waters to around 6 PM
in the northern inner waters. With this band of strong winds ahead
of the cold front, southerly gusts to 45 kts are expected. A few
places may see even higher gusts to 50 kts or more, especially in
and near heavier showers which can bring some of the stronger winds
aloft down to the surface. Seas will respond quickly, and wind waves
of 12 to 15 ft with a period of around 12 seconds are expected.

After this first burst of strong winds, a brief lull is expected
before another round of strong winds associated with a bent back
occluded front arrives. This area of southwesterly winds, which
is expected to overspread the waters from west to east between 8
PM Saturday and 3 AM Sunday, has the potential to bring a several
hour period of sustained 30 to 40 kt winds with gusts to 50 kts.
It is still uncertain where the strongest winds will occur due to
some differences in the location of the low among the weather
models, but at this time it looks as though most of our waters
(with exception to the far northern waters) will take a hit from
the strong winds associated with this weakening sting jet feature.
In addition, given the higher winds generated by this feature
further offshore, a fresh westerly swell will build seas into the
20 to 23 ft range, especially across the outer waters.

There's a short break in winds Sunday afternoon and evening, and
seas should ease in response. However, Sunday night southerly winds
are forecast to pick back up in response to an approaching cold
front associated with another low pressure system located further
northwest in the Gulf of Alaska. Ultimately, another period of
Gale Force winds is possible Sunday night through Monday
afternoon. In addition, a westerly swell from the same system well
to our northwest will drive seas back up into at least the low to
mid teens by early Tuesday morning. Seas are unlikely to fall
below 10 ft through the end of the day Wednesday, and it's
possible that they will stay at or above 10 ft even through the
end of the work week. -Bumgardner

&&

.BEACH HAZARDS...Hazardous beach conditions are likely late
Saturday night through Sunday afternoon as a westerly swell moves
onshore. This will produce marginal high surf advisory conditions
for beaches between Astoria and Florence with breakers up to 23
ft possible. The large area of strong westerly winds coupled with
a growing westerly swell could produce favorable conditions for
dynamic fetch to occur leading to higher wave heights and
potentially higher breakers. This would push conditions into
Advisory criteria with breakers around 25 ft but only for a brief
period, 3 maybe 6 hours. Either way people can be swept off rocks
and jetties and drown while observing high surf. Higher than
normal water run-up is possible on the beaches and low-lying
shoreline. -BMuhlestein

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 2 PM PST this afternoon to 5 AM PDT
     Sunday for Central Oregon Coast-North Oregon Coast.

     Winter Weather Advisory from 7 PM PST this evening to 5 PM PDT
     Sunday for Cascades in Lane County-Northern Oregon Cascades.

WA...Winter Weather Advisory from 7 PM PST this evening to 5 PM PDT
     Sunday for South Washington Cascades.

PZ...Small Craft Advisory from 8 PM PST this evening to 5 AM PDT
     Monday for Columbia River Bar.

     Small Craft Advisory until 10 AM PST this morning for coastal
     waters from Cape Shoalwater WA to Florence OR out 60 nm.

     Gale Warning until 8 AM PDT Sunday for coastal waters from Cape
     Shoalwater WA to Florence OR out 60 nm.

&&

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