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.
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.
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.
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, 3 hours 37 minutes earlier.
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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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.
&&
TJ6 high wind, 2 strong wind. Local standard time, as filed.
The Portland ASOS (KPDX) recorded max sustained winds of 41 mph with a peak gust of 52 mph.
Fairly widespread tree damage, and power outages in the area caused by down trees, power lines. Many areas of wind damage subsequently burned.
The Horse Creek RAWS (HSFO3) recorded a peak gust of 66 mph.
An IMET on the Holiday Farm Fire took some pictures as well as estimated wind gusts from observations and RAWS sites that are likely lost to the fire. Attached pictures might not be precisely located within the zone as information was taken from unknown exact locations.
An IMET on the Holiday Farm Fire took some pictures as well as estimated wind gusts from observations and RAWS sites that are likely lost to the fire. Attached pictures might not be precisely located within the zone as information was taken from unknown exact locations.
The Mount Hebo (AR658) location recorded a max sustained wind of 48 mph with a max wind gust of 92 mph.
The Tillamook AWOS (KTMK) recorded a peak wind gust of 52 mph.
Newport South Beach (SBEO3) reported a max sustained winds of 41 mph with gusts up to 58 mph. Yachats (E1135) recorded a max sustained winds of 32 mph with gusts up to 75 mph. Lincoln City (AR659) recorded a peak wind gust of 61 mph.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| High Wind, North Oregon Cascades Foothills | 2020-09-07 | Other | Direct | ||
| High Wind, North Oregon Cascades Foothills | 2020-09-07 | Other | Direct | ||
| High Wind, North Oregon Cascades Foothills | 2020-09-07 | Other | Direct | ||
| High Wind, North Oregon Cascades Foothills | 2020-09-08 | Other | Direct | ||
| High Wind, North Oregon Cascades Foothills | 2020-09-08 | Other | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2020Every state in 2020This day in weather historyWarnings in Oregon, September 2020
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: 922949, 922952, 922953, 922954, 922956, 922958, 922957, 922948.