A potent fast-moving Pacific storm moved through the region from the 4th into the 5th bringing strong winds to mainly wind-prone areas of northeast California and the Sierra Nevada, with light mountain snow mainly focused in the Lake Tahoe Basin and the northern Sierra.
Every event with a place to put it; 5 filed by county or forecast zone are drawn at its center, in a lighter ring. 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 REV wrote it up.
A potent fast-moving Pacific storm moved through the region from the 4th into the 5th bringing strong winds to mainly wind-prone areas of northeast California and the Sierra Nevada, with light mountain snow mainly focused in the Lake Tahoe Basin and the northern Sierra.
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 Jan 3, 2:18 PM PST, 9 hours 42 minutes earlier.
Area Forecast Discussion
National Weather Service Reno NV
218 PM PST Sun Jan 3 2021
.SYNOPSIS...
A fast moving Pacific storm will move through Monday with strong
winds, valley rain and mountain snow. Clearing for Tuesday into
Wednesday with a couple weak systems possible Wednesday night and
on Friday. Some increase in wind along with showers are possible
with each storm.
&&
.SHORT TERM...
Few changes needed to the going forecast for the storm on Monday.
That continues to be the main focus with the main change to have
the peak winds occur about 3-4 hours earlier. As of now we expect
the maximum winds for the storm to occur from late morning through
mid-afternoon. Here are some details for the Monday storm:
* WINDS: Peak winds from the southwest were maintained from the
previous shift, but were adjusted to occur ahead of the front
and not with it. Timing is as above with peak gusts still near
55 mph for most valley locations and 70-75 mph for wind prone
locations. Some wind damage is possible with a few downed power
lines and tree limbs, along with minor fence damage. Sierra
Ridge gusts will peak over 100 mph. Travel will be affected,
especially along the Highway 395 corridor.
* PRECIP/SNOW: Snow levels still look to be 6000-7000 feet from
north to south for much of the event. This will limit most snow
above that level as they will not fall until the front passes in
the late afternoon. Total precip amounts are still 1-1.5 inches
near the Sierra Crest with about half that in the Tahoe Basin.
1/4 to 1/2 inch for NE California and up to 1/4" for western
Nevada. Spillover will occur, but be confined to the front
itself. Snow amounts still look to be near or a little over a
foot for the high Sierra and a few inches from 6-7000 feet
depending on timing of the changeover. Still only think 2-4
inches at lake level for the Tahoe Basin.
The storm rapidly winds down Monday evening. Temperatures are
likely to get quite cool as skies clear, but likely not much below
average. Dry and seasonably cool for Tuesday with light winds. X
.LONG TERM...Wednesday through next weekend...
Mainly minor adjustments were made to the long term forecast
based on latest model trends. While system performance next week
will be hampered by wave displacement from parent low due to a
more northerly directed storm track, precipitation amounts are
trending modestly wetter. As a result, precip totals were nudged
upwards somewhat. However, for context, the mid week and Friday
waves have much less upper level support than tomorrow's system
and do not appear as impactful. With upper level support well
displaced, winds will also not be as strong, but will become gusty
along ridgetops and breezy for valleys with each wave.
Models show energy directed well northward for the first system
Wednesday into Thursday resulting in more a nuisance scenario for
Sierra travelers. QPF totals are light since the wave breaks
apart as it loses upper level support, but snow showers will be
possible over 6000 ft with minor accumulation projected around an
inch or so (most likely scenario). Probabilities for higher
amounts drop quickly in model scenarios with only a around a 20%
chance of 6 inches above 7000ft.
QPF and probabilities for around 6 inches above 7000ft are
increasing for Friday's quick-hitting system. However, today's runs
are the first step towards this outcome leaving forecaster certainty
on the lower end. Those with Friday travel plans in and around the
Sierra should check back for updates. Boyd
&&
.Aviation...
Today will be relatively quiet with plenty of mid-high cloud cover
but generally VFR conditions. Monday will still have significant
aviation-related weather impacts including windy conditions
everywhere, a rain/wet snow mix for the Sierra terminals producing
IFR vis/cigs and possible slush accumulations late in the day, and
periods of rain for lower elevations producing MVFR/brief IFR. Rain-
snow line elevations will vary between 6000-7000 ft, before dropping
to near 5000 feet at the end of the precip event early Monday
evening. LLWS can be expected for terminals north of Highway 50
after 12Z Monday morning and later in the afternoon for KMMH as
the wave pushes into the region. MJD/Boyd
&&
.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory from 4 AM Monday to 4 AM PST Tuesday
NVZ002.
Wind Advisory from 10 AM Monday to midnight PST Monday night
NVZ001-004.
Wind Advisory from 4 AM to 7 PM PST Monday NVZ003-005.
CA...Winter Weather Advisory from 4 AM Monday to 4 AM PST Tuesday
CAZ072-073.
Winter Weather Advisory from 4 AM Monday to 4 AM PST Tuesday
CAZ071.
Wind Advisory from 4 AM to 7 PM PST Monday CAZ070.
&&
For more information from the National Weather Service visit...
http://weather.gov/renoThe national radar mosaic for the moment the first event began.
3 high wind, 2 winter weather. Local standard time, as filed.
Light to moderate snow affected the Lake Tahoe region with up to 12 inches at Squaw Valley Ski, 8 inches at Homewood Ski, 6 inches at Northstar Ski, 5 inches at Independence Lake, 3 inches at Heavenly Ski, and 2 inches at Tahoe Donner Ski.
Light snow fell at Mammoth Mountain Ski the 4th into the early morning hours of the 5th with 4 inches measured at the base of the resort.
Widespread gusts of 45-57 mph in the Sierra Valley and along the US 395 corridor between Susanville and the California-Nevada state line. A peak wind gust of 58 mph was measured by the LIB24 mesonet 3 miles southeast of Dog Valley.
Widespread high winds impacted the Eastern Sierra and Mono County during the morning and afternoon of January 4. 108 MPH at Mammoth Mountain and 79 MPH at Conway Summit were notable observations. June Lake Fire Department reported multiple 2-foot diameter trees blown down or snapped in high winds.
Widespread gusts of 40-55 mph were seen across much of the Greater Lake Tahoe Area. Wind gusts up to 54 mph were seen along the surface of Lake Tahoe. A peak wind gust of 136 mph was measured by the Siberia mesonet atop Squaw Valley.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, January 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: 948269, 948270, 948267, 948268, 949128.