High Wind in Washington, September 7 to 8, 2020

Name: High Wind in Washington, September 7 to 8, 2020
Start: 2020-09-07T18:28
End: 2020-09-08T10:00
Location: Washington

September 7 to 8, 2020 · NWS PQR · 3 events in 3 counties and zones

The toll

Deaths: 0
Injuries: 0
Property damage: $1.1 billion
Crop damage: None recorded
Events: 3

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS PQR wrote it up.

After a period of upper level ridging brought a return to above normal temperatures in early September, very strong easterly downslope and offshore winds off the Cascades and Coastal Ranges occurred. Winds increased rapidly during the afternoon and evening of September 7 with the passage of an unseasonably strong backdoor cold front, and persisted through much of the following day. This resulted in extremely critical fire weather conditions when the strong winds combined with extremely low relative humidity and exceptionally dry existing fuel conditions. The result was explosive growth of ongoing wildfires, and the new start and explosive spread of numerous new wildfires. Widespread wind gusts from 50-70 mph were common on ridge tops and numerous other in exposed areas, including portions of the greater Portland metro area, the Willamette Valley, and areas of the Oregon coast. Strong winds caused widespread damage to trees, and downed numerous power lines across the region, which started at least 13 additional wildfires. Large portions of the cities of Detroit, Mehama, and Gates were destroyed, and significant portions of Idanha, Mill City, and Lyons also burned. Resultant large wildfires included these named incidents - In Oregon: Beachie Creek, Chehalem Mountain/Bald Peak, Riverside, and Lionshead, and in Washington: Big Hollow. Rapidly spreading wildfires resulted in multiple fatalities, hundreds of displaced persons for many weeks, and billions of dollars in damage.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Portland, OR wrote its last area forecast discussion before the first event at Sep 7, 1:58 PM PST, 4 hours 30 minutes earlier.

Area forecast discussion, Sep 7, 1:58 PM PST, 4 hours 30 minutes before

Area Forecast Discussion
National Weather Service Portland OR
258 PM PDT Mon Sep 7 2020

.SYNOPSIS...A unusually potent east wind event is ramping up this
afternoon. East winds will likely peak later tonight
and early Tuesday morning. Extreme fire danger and locally damaging
winds  are likely. Warm and dry weather appears likely through the
end of the week.

&&

.SHORT TERM...Tonight through Thursday...The cooler and dry air mass
well into eastern WA/OR this afternoon and is filtering into west of
the Cascades. In addition to the strong gusty winds in the Columbia
Basin, dew points are a good indicator of the air mass boundary.
There dewpoint have dropped into the low 30s. Satellite loop shows
clouds developing along the frontal boundary with the leading edge
now now approaching the Cascade crest.	 Rattlesnake Ridge WA is
gusting to 74 mph at noon, this is an exposed ridge south of Hanford
WA.  CIRA Dust and natural color satellite imagery show dust smoke
from eastern WA fires drifting toward the west.	 So hazy skies will
be increasing through Tue. Hood River and Skamania, and possibly
eastern Multnomah & Clackamas counties may see reduced visibility.
With the increasing wind and cold air advection, would not be
surprised to see some dust kicked up off Mt. Saint Helens tonight and
Tue.

Overall the forecast appears on track so no changes to warnings at
this time.   The KOTH-KGEG pressure gradient switched from positive
to negative 17Z and at 21Z at -9.0 mb.  Models fairly close with RAP
closest to obs. NAM is a couple of millibar too high.  The RAP peaks
near -23 mb, NAM -21 mb, GFS -21 mb between 3-5 am Tue.	BUFR
soundings near and surrounding the Gorge - between Mt. Adams and Mt.
Hood - show winds ramping up quickly early this evening.  The lower
level jet at 900 mb or roughly 2500 ft MSL winds plateauing around 2
am at 65-70 kt then subsiding after 6 am Tue.	There is no big
changes in the models so still looks good for 40 to 60 mph east wind
gusts will develop with gusts 60 to 80 mph expected on exposed
ridges so High Wind Warning look good.  Strong winds will affect
areas west of the Gorge to the coast as well affecting the
Portland/Vancouver metro area with gusts 40 to 55 mph, but may also
see gusts 60-65 mph across the higher terrain like the west hills
and areas near the Gorge. Similar winds extend across the north
coast range to the higher portions of the north coast zone.  In
other words, the High Wind Warnings currently in good shape.

Fire: A Red Flag Warning continues into Wed across entire forecast
area due to a combination of dry fuels, very low humidities, and of
course wind. It's a rare occurrence (likely a first) for Extremely
Critical fire category for our area from Storm Prediction Center.
Critical fire weather continue into Wed however. Since warm dry
conditions continue into Thu so may still see continuation of high
fire concerns. But fortunately winds will be considerably weaker.

Heat: A Heat Advisory for the central coast into Tue due to the
strong offshore flow and resulting downslope warming off the coast
range combined with a thermal trough right along the coast. 850 mb
temps Tue in that area are around 20-23 C. Wed into Thu the heat
shifts inland with some relief for the coast as a southerly wind
reversal occurs to bring a shallow marine layer along the coastline.
Models differ in the timing but the NAM which usually performs well
is showing this development.  The south and central Willamette
Valley may reach Heat Advisory criteria Wed then expand to include
north Willamette Valley/Clark county Thu.

.LONG TERM...Thursday night through Monday...More cooling looks
likely Fri into Sat with weak onshore flow and lowering 500 mb
heights along with weak embedded shortwaves.  ECMWF and GEFS ensemble
show 850 mb temps gradually lowering into the weekend for continued
warm but not hot weather.   Shallow morning inversions	 Fri - Sun
may lead to lower somewhat stagnant air for the interior valley with
potential for lower air quality. /mh

&&

.AVIATION...The 00Z TAF period is highlighted by an impressive
east wind event beginning early this evening and continuing into
tomorrow.

Offshore flow will begin to strengthen this afternoon with
easterly to northeasterly wind gusts between 20 and 35 kt
impacting most terminals this evening. Locally stronger wind
gusts between 40 and 50 kt will be possible across the
Portland/Vancouver metro after 00Z Tuesday. In addition, expect
very strong low level wind speed shear on the order of 30 to 60
kt at around 2000 ft across portions of NW Oregon and SW
Washington.

The easterly winds will also bring upper level smoke and haze
into the Willamette Valley from nearby fires. In addition,
blowing dust from the Columbia Basin could produce hazy
conditions across the northern Valley and Columbia River Gorge
this evening. Aside from areas with smoke, skies will be clear.
Visibility reductions are not expected at the terminals at this
time.

Refer to http://weather.gov/zse for detailed regional aviation
weather and hazard information.

KPDX and APPROACHES...Upper level smoke will continue over the
next 24 hours, with increasing offshore flow this afternoon and
evening. This offshore wind event will bring very gusty east
winds to the terminal beginning late Monday afternoon, with
occasional gusts to around 50 kt expected late this evening
through tonight. Very strong low level wind shear on the order of
30-50 kt over 1000-2000 feet will likely be present over the
terminal for much of the night. -TK/DDH

&&

.MARINE...An unusually strong and impressive offshore wind event
is expected to unfold this evening and continue through Tuesday
night. Easterly wind gusts between 25 and 30 kt should be
widespread across the waters, with a few gusts approaching 35 kt.
Pockets of stronger Gale Force wind gusts will be possible
downwind of the coastal river gaps such as the mouth of the
Columbia River, Tillamook Bay, and Yaquina Bay. This will bring
another round of steep, choppy seas as wave heights rise to 7 to
9 ft with a period around 8 seconds. Therefore, a Small Craft
Advisory is in effect for all waters through this evening through
Tuesday night.

Offshore flow should weaken considerably on Wednesday as the
surface pressure gradient begins to relax over the waters. This
should result in winds falling below advisory thresholds and seas
dropping below 5 ft. By late Wednesday, low pressure is forecast
to drift off the Oregon coast and bring southerly winds across
the waters Thursday into Friday. -TK/DDH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 PM PDT Wednesday for Central Oregon
     Cascade Foothills-Central Oregon Coast-East Slopes of the
     Central Oregon Coast Range-Mt. Hood National Forest West
     of Cascade Crest-North Oregon Cascade Foothills-North
     Oregon Coast-North Oregon Coast Range-Willamette National
     Forest-Willamette Valley.

     High Wind Warning until 1 PM PDT Tuesday for Coast Range of
     Northwest Oregon-Greater Portland Metro Area-North Oregon
     Coast-Northern Oregon Cascade Foothills-Northern Oregon
     Cascades.

     Heat Advisory until 11 PM PDT Tuesday for Central Coast Range
     of Western Oregon-Central Oregon Coast-North Oregon Coast.

WA...Red Flag Warning until 8 PM PDT Wednesday for Clark County
     Lowlands-East Willapa Hills-Eastern Gifford Pinchot
     National Forest Mt Adams Ranger District-Extreme South
     Washington Cascades and Foothills-South Washington Coast
     and West Willapa Hills.

     High Wind Warning until 1 PM PDT Tuesday for Greater Vancouver
     Area-South Washington Cascade Foothills-South Washington
     Cascades.

PZ...Small Craft Advisory until 5 AM PDT Wednesday for coastal
     waters from Cape Shoalwater WA to Florence OR from 10 to
     60 NM.

     Small Craft Advisory until 5 AM PDT Wednesday for coastal
     waters from Cape Shoalwater WA to Florence OR out 10 NM.

&&

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In the hours before

Local storm report, Sep 7, 5:35 PM PST, 53 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PORTLAND OR
635 PM PDT MON SEP 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0628 PM     NON-TSTM WND DMG 2 SW PROEBSTEL          45.64N 122.48W
09/07/2020                   CLARK              WA   PUBLIC

            LARGE TREE SNAPPED IN HALF NEAR LACAMAS
            CREEK.

&&

TJ

Local storm report, Sep 7, 5:51 PM PST, 37 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PORTLAND OR
651 PM PDT MON SEP 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0630 PM     NON-TSTM WND DMG 2 SSW BEAVERTON         45.45N 122.83W
09/07/2020                   WASHINGTON         OR   PUBLIC

            LARGE TREE DOWN NEAR SW HART AND SW
            SORRENTO.

0615 PM     NON-TSTM WND DMG 2 NNW PORTLAND DOWNTOWN 45.55N 122.70W
09/07/2020                   MULTNOMAH          OR   PUBLIC

            TREE DOWN IN NW PORTLAND AT EVERETT ST AND
            22ND.

0535 PM     NON-TSTM WND DMG 3 NE ROCKCREEK          45.58N 122.83W
09/07/2020                   MULTNOMAH          OR   NWS EMPLOYEE

            GERMANTOWN ROAD CLOSED DUE TO A DOWNED TREE.

&&

Local storm report, Sep 7, 6:10 PM PST, 18 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PORTLAND OR
710 PM PDT MON SEP 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 PM     NON-TSTM WND DMG 1 S WILSHIRE PARK       45.54N 122.63W
09/07/2020                   MULTNOMAH          OR   PUBLIC

            LARGE TREE SNAPPED IN HALF AT GRANT HIGH
            SCHOOL (GRANT PARK) IN NE PORTLAND.

&&

Local storm report, Sep 7, 6:13 PM PST, 15 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PORTLAND OR
713 PM PDT MON SEP 7 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0712 PM     NON-TSTM WND DMG 2 SSW ALOHA             45.47N 122.88W
09/07/2020                   WASHINGTON         OR   PUBLIC

            TREE DOWN ON 198TH & FARMINGTON IN
            BEAVERTON.

&&

Event by event

3 high wind. Local standard time, as filed.

High Wind, Southern Washington Cascade Foothills

When: September 7, 6:28 PM PST to September 8, 8:41 AM PST
Where: Southern Washington Cascade Foothills forecast zone
Measured: 55 kt (63 mph) estimated gust
Property damage: $1,000
Reported by: Trained Spotter

Estimated Beaufort 9-10 scale winds reported by a trained storm spotter (spotter had many years of schooner sailing experience before moving to the Pacific NW). This estimation was done after watching multiple large Douglas Fir trees swaying in the wind. The top of one large Douglas Fir trees was snapped off.

High Wind, Greater Vancouver Area

When: September 7, 6:50 PM PST to September 8, 6:32 AM PST
Where: Greater Vancouver Area forecast zone
Measured: 52 kt (60 mph) measured gust
Property damage: $100 million
Reported by: Mesonet

The Glenn Jackson I-205 Bridge over the Columbia River (ODT08) recorded a max sustained wind of 45 mph with a max gust of 60 mph. The max wind gusts at this location were likely higher as the station lost power a few hours into the event and thus stopped reporting.

High Wind, South Washington Cascades

When: September 8, 2:00 AM PST to 10:00 AM PST
Where: South Washington Cascades forecast zone
Measured: 58 kt (67 mph) measured gust
Property damage: $950 million
Reported by: RAWS

The Three Corner Rock RAWS (TRKW1) recorded a max sustained wind of 37 mph, and a peak gust of 67 mph.

What these are

High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Washington in 2020 Every state in 2020 This day in weather history Warnings in Washington, September 2020

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 922951, 922950, 922959.