As an upper trough dug south and east into the western US, an attendant cold front swung across northern CA early morning on the 29th and continued across western NV later that morning through the afternoon. This last in a series of AR supported storm systems brought higher elevation snow, valley rain showers, and strong southwesterly winds to the region.
Every event with a place to put it; 3 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.
As an upper trough dug south and east into the western US, an attendant cold front swung across northern CA early morning on the 29th and continued across western NV later that morning through the afternoon. This last in a series of AR supported storm systems brought higher elevation snow, valley rain showers, and strong southwesterly winds to the region. This round of strong southwest winds included gusts up to 40-50 mph in western NV valleys, as well as 120+ mph wind across Sierra ridges. Wind prone areas also saw a 40-60% chance for peak gusts around 60+ mph.
Impacts included hazardous driving conditions, especially for high profile vehicles, frequent periods of mountain wave turbulence, rotors, and LLWS for aviation concerns, choppy lake conditions on larger area lakes, and periods of blowing dust in dry lake beds/playas for the Basin and Range. Other potential impacts included downed trees, powerlines, and power outages. Blended guidance projected a 40-60% chance for up to 4-8 inches of snowfall at higher passes such as Donner Summit, Echo and Carson Pass. The gusty southwest winds and periods of moderate snow created additional travel challenges over higher mountain passes before tapering off overnight on the 29th.
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 Dec 29, 2:38 AM PST, 3 hours 22 minutes earlier.
Area Forecast Discussion
National Weather Service Reno NV
238 AM PST Sun Dec 29 2024
.SYNOPSIS...
* Another storm system will bring Sierra snow, valley rain showers,
and widespread and potentially damaging winds today.
* A weak front will bring increased shower chances over northeast
California close to the Oregon border New Year's Day. Otherwise,
dry and mild weather returns for much of this week.
&&
.DISCUSSION...
Today’s Storm System Update:
Current IR satellite imagery and radar show the next storm system
moving into northern California. This last in a series of AR
supported storm systems will bring more higher elevation snow,
valley rain showers, and strong southwesterly winds to the region.
As the upper trough and attendant cold front push inland this
morning, thermal and pressure gradients will tighten across the
Sierra and western Nevada. This will produce a strong southwest flow
aloft that will mix down into valley areas across western Nevada
this morning into the afternoon.
* Winds: This round of strong southwest winds with produce gusts up
to 40-50 mph in western NV valleys, and 100+ mph across Sierra
ridges. Wind prone areas along the I-580 corridor through the
Washoe Valley, Highway 395 corridor through Douglas County into
Mono County, and Highway 95 through Mineral County will once again
see a 60-70% chance for peak gusts reaching 60-70 mph. Look for
wind gusts to gradually dissipate to 20-30 mph, and shift from the
northwest early this evening as gradients relax behind the exiting
cold front. A High Wind Warning remains in effect for the Sierra
Front, Mono, and Mineral Counties with Wind Advisories for all
other Basin and Range forecast zones.
* Impacts: Be prepared for hazardous driving conditions in wind
prone areas, especially for high profile vehicles. Aviation
interests should be prepared for frequent periods of mountain
wave turbulence, rotors, and LLWS. Wind gusts reaching 50 mph
will bring choppy lake conditions with wave heights of 2-5 feet
on larger area lakes. Also, look for brief periods of blowing
dust rising from areas dry lake beds/playas across the Basin and
Range. Other potential impacts include downed trees, powerlines,
and power outages.
* Precipitation: Look for light to moderate snow with brief snow
rates 1-2 inches per hour for higher mountain passes like
Donner, Carson, Echo, and Mt Rose passes late this morning into
the afternoon. Recent blended guidance also shows a marginal
increase in liquid precipitation amounts along and west of the
Sierra Crest above 7000 feet. High resolution ensemble and
blended projections still show a 70-80% chance for up to 8-12
inches of snowfall falling on higher mountain passes. Look for a
slushy, wet snowfall to begin around 4-7 AM this morning for
mountain passes that increases in intensity late morning into
the afternoon before tapering off this evening. A Winter Weather
Advisory remains in effect for for Lassen, eastern Plumas
Counties, as well as the Lake Tahoe Basin to include eastern
Alpine County from 5AM to 8PM with snow impacts staying mostly
above 5500-6000 feet.
* Impacts: Gusty southwest winds and periods of moderate snow may
create additional travel challenges over higher mountain passes
this morning and afternoon, before tapering off tonight.
Travelers should anticipate chain controls, delays, and
hazardous driving conditions over mountain passes. It is advised
to check road conditions with CalTrans and NDOT before
traveling into the mountains.
Monday Onward Through the New Year:
* Drier and milder conditions return early next week as high
pressure ridges into the region. A quick hitting backdoor short
wave trough may bring an increased chance for a light shower or
two nearer the Oregon border on Wednesday. Another weak storm
system looks to brush by the region later this week bringing light
snow accumulations to higher elevation areas along the Sierra
crest.
Otherwise, look for drier conditions and a return of valley
inversions under clear skies and lighter winds to ring in the New
Year. Please stay updated on changing conditions and travel safely!
-Amanda
&&
.AVIATION...
Through 12Z Monday:
* Strong Southwest Winds: Widespread gusts 35-45 knots across the
Sierra Front, 30-40 knots at Tahoe area terminals, and 55-60
knots in the Eastern Sierra.
* Mountain Wave Turbulence/LLWS: FL100 winds will approach 65-70
kts through 30/00Z, delivering severe mountain wave activity,
downdrafts, and LLWS region-wide, especially along the Sierra
crest and Sierra Front east. Pilots should anticipate hazardous
conditions when climbing/descending into area terminals.
* Reduced Visibility/CIGs in Rain and Snow: Showers will at times
reduce the visibility/CIGs to MVFR for KRNO/KCXP/KMEV, and at
times to IFR/LIFR for Sierra terminals. Mountain obscurations
will also be present in the Sierra and along the Sierra Front.
Snow levels will lower to 4500-6000 ft Sunday afternoon, with
light to moderate snow possible at KTRK, KTVL, and KBAN.
* Snow Accumulation chances: 10-20% up to 1 inch at KTRK, 40-50% for
1-2 inches at KTVL, and 30-40% 3-4 inches at KBAN.
Pilots should plan for rapidly changing conditions today due to
impending winter weather conditions.
-Amanda
&&
.AVALANCHE...
Snow amounts have come up moderately above 7000 ft with the latest
forecast run. A winter storm will bring rapidly changing weather
conditions across the Sierra Nevada through today. Key impacts
include lowering snow levels, strong winds, light to moderate
precipitation, and cooling temperatures near freezing.
Central Sierra Nevada (Yuba Pass to Ebbetts Pass, including the
Greater Lake Tahoe Area):
...Winter Weather Advisory in effect from 5 AM to 8 PM PST today...
* Snow levels will start at 6500-7000 ft, and lower further to
5000- 5500 ft by this evening. Winds ill strengthen throughout
the period, with mid-slope winds peaking at 25-35 mph with gusts
up to 60 mph. Ridgetop winds will be stronger, increasing to
45-65 mph today with gusts over 100 mph. Wind shear at ridgetop
levels will persist, exceeding local thresholds (greater than 30
mph for 3 hours or more) with a greater than 95% probability.
* Precipitation will intensify today, bringing liquid equivalent
totals of 0.75-1.25 inches, with greater than 90% probability of
SWE exceeding 0.5 inches in 24 hours. Snowfall rates will at
times exceed 1 inch per hour (0.1" SWE/hr) between 9 AM and 6 PM
PST Sunday, especially above 7000 ft, with greater than 60%
probability of meeting heavy snowfall thresholds. Total snowfall
is expected to range from 4-10 inches between 7000-8000 ft and
8-12 inches above 8000 ft, with localized amounts up to 18
inches. Skies will remain mostly overcast, limiting solar
warming, and temperatures will near freezing at 7000 ft by
Sunday evening, creating a rain-to-snow transition zone.
Eastern Sierra Nevada (Walker to Bishop Creek):
...High Wind Warning in effect from 4 AM to 7 PM PST Today...
* Snow levels will hover near 7000 ft by this evening. Southwest
winds will strengthen, with mid-slope gusts reaching 80-90 mph
today, while ridgetop winds reach 40-60 mph today, with gusts up
to 95 mph.
* Precipitation this morning will bring liquid equivalent totals
of 0.30-0.50 inches, with a greater than 50% probability of SWE
exceeding 0.25 inches in 24 hours. Snowfall rates may at times
reach 1 inch per hour (0.1" SWE/hr) between 12 PM to 4 PM PST
above 8000 ft, with a greater than 40% probability of meeting
heavy snowfall thresholds. Total snowfall will range from 3-6
inches above 8000 ft, with localized amounts up to 10 inches.
Skies will remain mostly cloudy to cloudy today, limiting solar
intensity. Temperatures will approach freezing near 7000 ft by
Sunday evening.
-Johnston/Amanda
&&
.HYDROLOGY...
Minor river rises are expected for the Susan River and the Pit River
through today, driven by increased runoff from precipitation and
snowmelt. Both rivers are forecast to remain below their
respective action stages, with no significant flooding
anticipated.
Susan River at Susanville:
* Forecast: The deterministic forecast projects a peak of
approximately 9.6 feet today, well below the action stage of
10.5 feet. There is less than a 2% probability of reaching the
action stage during this event.
* Impacts: Flows will rise significantly, reaching nearly four times
the current levels. While minor rises are expected, flooding is
not a concern.
Pit River at Canby:
* Forecast: The river is expected to peak near 7 feet today, below
the action stage of 7.5 feet. There is less than a 10% chance of
reaching the action stage.
* Impacts: Substantial increases in flow are expected, but flooding
is not anticipated. Any impacts will likely be minor and localized
to low-lying areas.
Residents and stakeholders should monitor updates as needed, though
no significant issues are expected from these river rises.
-Johnston/Amanda
&&
.REV Watches/Warnings/Advisories...
NV...Wind Advisory until 4 PM PST this afternoon NVZ005.
Winter Weather Advisory until 8 PM PST this evening NVZ002.
High Wind Warning until 7 PM PST this evening NVZ001-003.
Wind Advisory from 7 AM this morning to 7 PM PST this evening
NVZ004.
CA...Wind Advisory until 4 PM PST this afternoon CAZ070.
Winter Weather Advisory until 8 PM PST this evening CAZ071-072.
High Wind Warning until 7 PM PST this evening CAZ073.
&&The national radar mosaic for the moment the first event began.
2 high wind, 1 winter weather. Local standard time, as filed.
The public located at the Palisades Tahoe Ski Base, CA, and the public located 1.0 mi SSW of the Northstar Ski Base on the upper mountain reported 24 hour total snowfall amounts of 8.0 inches, and 6.0 inches respectively.
Mesonet station (HVRGM-Mid-Station Gondola Weather Station) located 1.0 mi ENE of the Heavenly Ski summit reported a peak wind gust 91 mph.
Mesonet station (MTH03) located 1.7 mi SE of Mammoth Mountain Ski Summit, and mesonet station (XMLC1 Mill Canyon) located 4.0 mi SSW of Walker, CA, reported peak wind gusts of 83 mph, and 77 mph respectively.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2024Every state in 2024This day in weather historyWarnings in California, December 2024
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: 1230084, 1230082, 1230083.