Heavy rains produced by an atmospheric river brought river flooding to portions of northwest Oregon and southwest Washington.
Every event with a place to put it. Tap one for its entry below.
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.
Heavy rains produced by an atmospheric river brought river flooding to portions of northwest Oregon and southwest Washington.
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 Nov 11, 4:00 AM PST, 1 hour earlier.
Area Forecast Discussion
National Weather Service Portland OR
400 AM PST Thu Nov 11 2021
.SYNOPSIS...A warm front will move northward into southwest
Washington this morning. This front will be enhanced by an
atmospheric river, resulting in periods of moderate to heavy rain
through Friday, especially for locations to the north of Salem. High
pressure will bring a break from the rain this weekend, except for
southwest Washington zones which will most likely see precipitation
return by Sunday. Then, a cold front will bring widespread
precipitation to the region on Monday and set the stage for a cool
and showery weather pattern heading into Tuesday and Wednesday.
&&
.SHORT TERM...Tonight through Saturday night...Early Thursday
morning, a warm front was draped across northwest Oregon, somewhere
in between Portland and Salem. This warm front continues to be the
focus for periods of moderate to heavy rain, which has been enhanced
by an atmospheric river and synoptic scale forcing for ascent.
Observed rainfall amounts as of 3 AM PST were highest over the higher
terrain of the central Oregon Coast Range and the central Oregon
Cascade foothills where 1.5-2.0 inches of rain had already fallen in
the past 12 hours. Observed rain rates have generally ranged between
0.1 and 0.5 in/hr, however locally higher rain rates have most likely
occurred with isolated thunderstorms. The aforementioned warm front
will swing into southward Washington by late morning as an upper
level shortwave rotating around a closed upper low over the Gulf of
Alaska acts to pull the warm front northward. This should result in a
short break from the persistent rain this afternoon for northwest
Oregon (aside from the far north coast/Coast Range and far north
Oregon Cascades).
Rain rates have the potential to increase slightly this evening
within the axis of heaviest rain as moisture transport peaks, but the
axis of heaviest rain will be relatively narrow. High resolution
model guidance suggests the axis of heaviest rain will be aimed at
southwest Washington and the far north Oregon coast/Coast Range today
through tonight. These locations could see additional 2-5 inches of
rain by Friday morning, with locally higher amounts possible over
higher terrain in the Willapa Hills and south Washington
Cascades/foothills. Potential hydro concerns remain for southwest
Washington and far northwest Oregon, which are discussed below in the
Hydrology section. The rest of the forecast area should see a decent
break from the persistent rain today and tonight with fairly minimal
hydro concerns. In fact, it will be rather mild this afternoon into
tonight as temperatures rise into the lower 60s (for locations to the
south of the warm front).
A cold front will gradually push southward across the forecast area
on Friday, bringing rain with it. While rain is expected to return to
all of northwest Oregon on Friday, this will also be when moisture
transport into the frontal boundary weakens and rain rates decrease.
So, hydro concerns on Friday should generally be limited to rivers
that reach flood stage Thursday night. High pressure should bring an
end to precipitation across all of northwest Oregon and southwest
Washington on Saturday, with rain chances increasing across
southwest Washington Saturday night. -TK
&&
.LONG TERM...Sunday through Wednesday night...Models and their
ensembles are in fairly good agreement that upper level ridging over
the western CONUS will bring dry and mild weather to the area on
Sunday, except for southwest Washington which could see rain return
due to a nearby warm front. Models are also in good agreement that an
upper level shortwave and attendant cold front will push across the
region early next week, but the timing of this cold front is
uncertain. At this time, this front is set to arrive sometime Monday
or Monday night. Once it does, expect widespread precipitation to
push into the region. This front will also bring in a cooler airmass,
allowing snow levels to lower to around 2500-3500 feet on Tuesday.
The EURO ensemble mean for 850 mb temperatures shows temperatures
lowering to around -3C by Tuesday morning. As a result, Tuesday
should be a noticeably cooler day with post-frontal showers around
the area. Wednesday is also shaping up to be a cool day, but it is
unclear if showers will linger or not. -TK
&&
.HYDROLOGY...At this time, the highest chance for river flooding
tonight and tomorrow is along the Grays River near Rosburg, the
Nehalem River near Foss, the Wilson River near Tillamook, the Trask
River near Tillamook, the Naselle River near Naselle, and the Willapa
River at Willapa. It now appears the potential for debris flows
over/near the recently burned areas in the Oregon Cascades is low, as
the heaviest rain looks to occur to the north of these burn areas.
While a cold front will push rain back to the south on Friday, this
will also be when moisture transport into the frontal boundary will
be weakening. So, rain rates should be on the decrease Friday and
hydro concerns should be mainly limited to rivers that end up
reaching flood stage Thursday night (which will still be running high
through the day on Friday). -TK
&&
.AVIATION...12Z TAFs: Warm front appears to have moved north of
KAST, but remain south of KHQM at the coast, but trails to the
southeast over the interior of western Oregon between KSLE and
KKLS. Rain rates have eased since midnight, but moderate rain
with isolated thunderstorms across Lane county continue. Next
slug of moisture seen on satellite to arrive 12-15Z to increase
rain rates again. Most of the CAM models indicating the axis of
heavier rain somewhere north of a KTMK-KSLE line, which slowly
lifts north through the morning. Flight conditions vary from
IFR/LIFR at the coast, MVFR/IFR north of KSLE, and generally VFR
to the south of KSLE. Expect these conditions will generally hold
for the next 6-8 hours. After about 18-20Z expect improvement as
the front lifts north of the area.
Areas of LLWS are likely through about 18-20Z Thu, mainly over
along the Columbia River from the Gorge to around KKLS where E-SE
surface wind is expected in conjunction with 30-35 kt south to
southwest wind between 1500 and 2000 ft AGL.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...Low MVFR to IFR expected through 18-20Z
this morning with moderate rain 12-18Z. After 18-20Z rain tapers
off and should see flight conditions improve. Will continue with
LLWS at the terminal and east approaches through 20Z due to
surface E to SE wind and S-SW wind 25-35 kt at FL015 to 020.
/mh Weishaar
&&
.MARINE...Will maintain Small Craft Advisory south to southwest
wind 20-25 kt through early Friday. A cold front slides south
over the waters Friday with winds easing. Weak high pressure
builds over the waters by Friday night then shifts inland as the
next front approaches. Expect to see south to southeast wind
gusting to 25 kt Sunday, then shift to westerly Monday.
Seas continue to subside, but will hold at or just above 10 feet
through today.
There will be a chance for thunderstorms through tonight. Some
of these storms could produce erratic wind gusts to 35 kt.
Weishaar
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Flood Watch from noon PST today through late Friday night for
Central Coast Range of Western Oregon-Central Columbia
River Gorge-Central Oregon Coast-Central Willamette Valley-
Coast Range of Northwest Oregon-Greater Portland Metro
Area-Lower Columbia-North Oregon Coast-Northern Oregon
Cascade Foothills-Northern Oregon Cascades-Upper Hood
River Valley-Western Columbia River Gorge.
WA...Flood Watch from noon PST today through late Friday night for
Central Columbia River Gorge-Greater Vancouver Area-I-5
Corridor in Cowlitz County-South Washington Cascade
Foothills-South Washington Cascades-South Washington Coast-
Western Columbia River Gorge-Willapa Hills.
PZ...Small Craft Advisory until 10 AM PST Friday for coastal waters
from Cape Shoalwater WA to Cascade Head OR out 60 nm.
Small Craft Advisory until 4 PM PST Friday for coastal waters
from Cascade Head OR to Florence OR out 60 nm.
Small Craft Advisory until 6 PM PST this evening for Columbia
River Bar.
&&
www.weather.gov/portland
Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortlandThe national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The Cowlitz River at Kelso (KELW1) rose above flood stage on the morning of the 11th, created at 21.5 feet around 2000PST on the 11th, then fell below flood stage on the morning of the 12th.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2021Every state in 2021This day in weather historyWarnings in Washington, November 2021
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: 994022.