A strong atmospheric river event produced a major heavy rain, high wind, and high elevation snow event for much of the region. Record-setting rainfall amounts for many areas of western Nevada and the Sierra Front in Douglas and Mono Counties.
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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 REV wrote it up.
A strong atmospheric river event produced a major heavy rain, high wind, and high elevation snow event for much of the region. Record-setting rainfall amounts for many areas of western Nevada and the Sierra Front in Douglas and Mono Counties.
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 Reno, NV wrote its last area forecast discussion before the first event at Oct 23, 11:43 AM PST, 12 hours 17 minutes earlier.
Area Forecast Discussion
National Weather Service Reno NV
1243 PM PDT Sat Oct 23 2021
.SYNOPSIS...
A weak wave is bringing a few showers to the region this afternoon
before the main event arrives overnight through Monday. A strong
atmospheric river will bring a deluge of rain, heavy mountain
snow, and gusty, potentially damaging, winds to the region.
Flooding is a concern, particularly near recent burn scars.
&&
.DISCUSSION...
Well, the next couple days should be interesting to say the least as
a strong atmospheric river slams into the west coast. If you haven't
done so yet, today is the final day to prepare by cleaning out your
gutters and drainage areas. If you need to cross the Sierra, it's
recommended to do so today, or wait until Tuesday.
LIQUID TOTALS:
Anticipated liquid totals remain largely unchanged with potential
for 6-10" along the Sierra crest, 3-6" of liquid into the Tahoe
Basin, 2-4" into northeast California and the Eastern Sierra of Mono
County, 0.75-3+" along the Sierra Front of Western Nevada, and 0.25-
1+" of liquid for the west central Nevada Basin and Range. At this
point, the greatest variation in upper/lower end qpf ranges lies in
areas near and east of US-395. This is likely due to shadowing in
higher resolution models and an uptick in wind speeds. A lot of
these high res models do tend to overshadow in the lee of the Sierra
and in this case, the synoptic set up and intense IVT would lead me
to favor the wetter scenarios. Just keep in mind, there is a 20%
chance for the drier scenarios to come to fruition.
If we are in the 50th-75th percentile range of the qpf guidance, 2-
day precipitation records [for the month of October] are possible.
Example, the current forecast of ~5" of liquid in Tahoe City is the
second highest 2-day October total in 112 year climo history (5.72"
is the current record). For Reno, the current forecast of near 2" of
rain would be a 2-day record for October, with the current record
1.67".
WINDS:
On the wind side of the spectrum, the HREF ensemble mean is
remarkably stronger with peak wind speeds for Sunday, which several
other models and the NBM agree with. Taking a look at ensemble
meteograms, the gusts have trended upward, but there is still a wide
spread with the upper end numbers, with 60+ mph only showing up in
about 15% of the solutions. Given the 700 mb jet streak peaking
around 65-75 kts, there is plenty of wind energy aloft and it won't
take much to mix down those stronger gusts.
The winds and the intense precipitation rates may be battling
each other, so it may be more intermittent rather than consistent
for those potentially damaging gusts. Even so, we have upgraded
the High Wind Watches to High Wind Warnings, with particular
concern along the western NV Sierra Front and Eastern Sierra
areas. We are still looking for gusts easily exceeding 100 mph
across ridgelines. These winds will bring periods of travel and
recreation concerns along with very bumpy flights for aviators.
FLOODING CONCERNS:
Despite the copious amounts of rain, the dry soils and large amount
of available storage in reservoirs will likely mitigate widespread
flood risks. That being said, recent ensemble scenarios from the
CNRFC indicate low end probabilities (~10% chance) for more
significant river rises, possibly even near or above monitor stage,
with a 5% chance of exceeding flood stage in some locations. Keep in
mind, this is likely worst case scenario, but it still bears
watching. Smaller creeks and streams and urban/poor drainage
flooding is certainly possible as well.
The greatest threat will be the recent burn scars -- really any
major burns in the past couple of years in the Sierra and/or
western Nevada foothills. This will be the first real test for
several burns, including but not limited to:
Caldor East, Tamarack, Slink, and Numbers. Dixie East, Beckwourth,
Sheep, and Walker saw minor impacts from the rain yesterday and now
have saturated soils, so this could further exacerbate things
there. Higher resolution model guidance is indicating rainfall rates
possible exceeding 0.5"/hour at times in northeast California and
the Sierra from early Sunday morning through Sunday evening.
Mud/debris flows or rock/tree falls are all on the table, so pay
extra attention if you are near a burn scar.
SNOW:
Snow levels will start rather high, around 9,000-10,000 feet, but
will fall late Sunday into Monday. The question at this point is how
fast will they fall. It looks like Sierra passes above 8000 feet
will start to see impacts Sunday night, with those closer to 7,000
feet before sunrise Monday. Snow levels will crash to around 5500-
6000 feet by Monday night, but the bulk of the precipitation will
have already fallen by this point. Snow totals for the high Sierra
(above 8,500-9,000') could reach 2-4+ feet, with the character being
heavy and wet. Communities in the Tahoe Basin and those along US-395
in the Eastern Sierra are likely to only see 1-5", but if snow
levels fall faster, those totals could easily double.
BEYOND THIS STORM:
The bulk of the AR moisture is out of the region by Monday afternoon
with lingering showers possible through Tuesday as the upper trough
transverses the region. Ridging builds over the west the middle into
the end of the week, but waves of moisture continue to stream into
the Pacific Northwest, which will likely keep high clouds around.
While a weak, fast-moving system can't be ruled out before
Halloween, overall there are no major storms on the horizon (beyond
the current one) through the start of November. -Dawn
&&
.AVIATION...
A weak system working through the area today will bring with it some
lowering CIGS and a chance for scattered showers. As the system
exits overnight there will be an increase in LLWS, decrease in VIS,
and the slight chance for showers remains. This system is closely
followed by the larger, more dynamic system associated with the
atmospheric river event we have been advertising.
This much stronger and wetter Pacific system will impact the
region Sunday morning into Monday with strong winds, mountain
obscuration and heavy rain for terminals across the region. Winds
and LLWS with this system will be of great concern throughout the
region. VIS/CIG could lower conditions across Sierra and western
NV terminals down to IFR/LIFR in heavier precipitation. There are
chances for accumulating snow at KTRK/KTVL/KMMH Monday.
HRICH
&&
.REV Watches/Warnings/Advisories...
NV...High Wind Warning from 5 AM to 11 PM PDT Sunday NVZ001-003.
Wind Advisory from 5 AM to 11 PM PDT Sunday NVZ004.
Flood Watch from late tonight through Monday morning NVZ002-003.
Winter Storm Warning from 5 PM Sunday to 11 PM PDT Monday above
7000 feet in NVZ002.
CA...High Wind Warning from 5 AM to 11 PM PDT Sunday CAZ073.
Flood Watch from 11 PM PDT this evening through late Sunday
night CAZ071.
Flood Watch from Sunday morning through Monday afternoon CAZ073.
Winter Storm Warning from 5 PM Sunday to 11 PM PDT Monday above
8500 feet in CAZ073.
Flood Watch from late tonight through Monday morning CAZ072.
Winter Storm Warning from 5 PM Sunday to 11 PM PDT Monday above
7000 feet in CAZ072.
&&
For more information from the National Weather Service visit...
http://weather.gov/renoThe national radar mosaic for the moment the first event began.
1 heavy rain, 1 high wind. Local standard time, as filed.
Several CoCoRahs Observers and Mesonet/ASOS sites reported rainfall amounts ranging from 1-2 inches near Fernley, 3-4 inches in and around Reno Metropolitan area, and 5-8 inches in the Foothills including around Verdi near the CA/NV border.
A gust of 78 mph was observed the evening of 24 OCT in Hawthorne, NV.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Nevada in 2021Every state in 2021This day in weather historyWarnings in Nevada, October 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: 986499, 987084.