Winter Weather in Nevada, February 1, 2025

Area Forecast Discussion
National Weather Service Reno NV
227 PM PST Fri Jan 31 2025

.SYNOPSIS...

* An active pattern returns today through next week with good
  chances for precipitation and strong gusty winds.

* Accumulating snowfall for this upcoming storm system looks to be
  confined to higher Sierra peaks with nearly continuous rainfall at
  lower elevations seeing a rise in regional creeks and streams.

* Dropping snow levels next week will lead to heavier snowfall
  potential and travel impacts in the Sierra.

&&

.DISCUSSION...

An AR supported storm system will bring higher elevation snow,
moderate to heavy valley rain, and strong southwesterly winds to the
region this weekend into Monday. A low pressure system dropping into
the Gulf of Alaska will swing into the Pacific Northwest by mid-
week, supported by a strong coupled jet stream system sporting a
150+ kt jet core, taps into a plume of subtropical moisture. The
resultant moderate to strong AR will ensure snow levels stay high
around 8000 feet Saturday and Sunday with periods of moderate to
heavy rain falling across lower Sierra elevations and adjacent
western NV valleys. The periods of heavier rainfall will be
accompanied with stronger winds over the region, especially Sunday
and again Monday where local thermal and pressure gradients
tighten across the Sierra into western Nevada. The mixing of these
stronger winds will bring gusty conditions down into valley areas
across western Nevada late Sunday morning that continues into the
evening and repeat Monday upon passage of a cold front passing
through the region that drops snow levels to lower elevation
areas.

* Precipitation:  Snow levels will stay around 8000 feet overnight
  Friday into Saturday morning, and stays at that height through
  Sunday. Anonymously high liquid precipitation amounts are
  projected to range from 2.00" to nearly 8.00" across the Sierra
  Crest Saturday through Sunday morning. Rainfall totals across
  western NV will range from a few hundredths of an inch across the
  Basin and Range to nearly 0.50"-1.00” over many areas of the
  Sierra Front to include Reno-Carson City. The heavier
  precipitation with this moist system will also bring increased
  stream flows for Lassen and Plumas counties as well as an
  increased chance for localize flash flooding especially in and
  near recent wildfire burn scars

* Higher Elevation Snow Lowers Monday Night: Heavy snow with brief
  snow rates briefly exceeding an inch per hour will bring several
  feet of accumulated snow to higher Snow mountain ridges above 8000
  feet from just south of the Lake Tahoe Basin northward across the
  northern Sierra into northeast CA. Higher mountain passes like
  Donner, Carson, Echo, and Mt Rose will still see a few inches of
  heavy, wet snowfall tonight into Saturday morning before snow
  levels increase through Saturday. Snow levels will begin to fall
  Sunday evening into Monday as the AR begins to sweep south over
  the region. Blended guidance projects a 30-40% for 3-5 plus feet
  of snow across higher margins of the Sierra Crest with lesser
  amounts at lower elevation areas. A Winter Weather Advisory has
  been hoisted for for Lassen, eastern Plumas Counties, as well as
  the Lake Tahoe Basin to include eastern Alpine County until 10 PM
  PST Saturday night. A Winter Storm Warning remains in effect late
  Saturday night through Monday evening.

IMPACTS:

* Periods of light to moderate snow over higher mountain passes
  Friday evening into the early morning hours Saturday could make
  for challenging travel conditions before snow transitions to
  mostly rain.

* Travelers should anticipate chain controls, delays, and
  hazardous driving conditions over mountain passes. It is advised
  to check road conditions with Caltrans and NDOT 511 before
  traveling into the mountains.

* Be prepared for hazardous driving conditions in wind prone areas,
  especially for high profile vehicles, especially during the late
  morning though early evening hours Sunday and Monday.

* Aviation interests should be prepared for frequent periods of
  mountain wave turbulence, rotors, and LLWS.

* The windy conditions will also bring choppy lake conditions
  with wave heights of 2-4 feet for larger area lakes through
  Sunday, except 2-5 feet on Sunday for Lake Tahoe.

* Other potential impacts include downed trees, powerlines, and
  power outages especially over higher terrain.  -Amanda

Tuesday Onward:

The gradual southwards shift of the upper level jet will allow
colder air drop southward from the upper low that is now projected
to still offshore the PacNW. Although there will still be a
strong jet/IVT pushing the moist plume of Pacific moisture into
CA, uncertainty remains elevated as to precipitation amounts and
timing. The take home message still remains the lowering snow
levels per the blended guidance and ensemble guidance ensures snow
impacts remain likely in the Sierra through the remainder of next
week. The continued strong dynamics coupled to a large scale jet
pattern producing through our area with additional periods of
intense precipitation rates across mountain areas and travel
difficulties farther south to include Mono-Mineral counties.

-Amanda

&&

.AVIATION...

* Widespread weather impacts to aviation will prevail for the next
  several days due to periods of moderate to heavy perception,
  gusty winds, mountain obscurations, LLWS, and turbulence. Expect
  flight delays, cancellations or diversions especially with the
  strongest wind days Late Saturday through Monday.

* RAIN/SNOW: For Sierra terminals, a light mix of rain/snow with
  transition to moderate to heavy rainfall through this afternoon.
  After which this period will largely be a rain event at all the
  terminals, with long periods of continuous rain especially for
  the Tahoe-Truckee area through Sun AM. Rain will most likely
  extend into the western NV terminals from Saturday morning thru
  Sat night. Rainfall will start at KMMH from late tonight and
  continue through late afternoon Sat.

* WINDS: Turbulence and/or shear will be widespread across the
  Sierra east into western NV through Monday, including mountain
  wave and rotor conditions. FL100 winds will be 50-65 kt with
  ridgetop wind gusts exceeding 90-100+ kt through Monday morning.
  SW-W surface winds increase at the main terminals with gusts 20-25
  kt through this afternoon, 25-35 kt Saturday afternoon, and 35-45+
  kt Sunday afternoon. Gusty wind conditions may also continue
  through Monday afternoon.

* Pilots should plan for rapidly changing conditions through Sunday.

-Amanda

&&

.AVALANCHE

Strong winds and heavy snow, with heavy rain possible, this weekend
for the Lake Tahoe area and southward. Additional rounds of snow
expected through next week.

* Snow levels: Levels slowly rise above 7000 ft today, and continue
  to climb above 8000 ft through Saturday. Locations south of Lake
  Tahoe will likely see snow levels upwards of 9000 ft. Levels may
  fluctuate but will remain elevated until Sunday.

* Snowfall totals: Accumulations in the lower elevations today may
  see up to 2 feet of snow. As snow levels rise, snow will be
  confined to the highest peaks where several feet (2-4 feet) of
  snow is likely through Saturday. The heaviest snowfall rates (max
  ~1.5"/hr) will occur tonight into early Saturday morning.

* SWE and SLR: Anywhere from 3-8" of SWE in the Sierra Avalanche
  Center Area. However, the highest SWE will be along the crests. In
  the Bridgeport Avalanche Center Area, SWE ranges between 2-5". The
  Eastern Sierra Avalanche Center Area will see 1-4". This system is
  relatively wet, so SLRs will be between 6:1 and 10:1.

-Giralte

&&

.HYDROLOGY...

* High confidence in significant rises on rivers and streams
  including nuisance flooding in poor drainage areas. These will be
  the highest flows for this water year in most areas, and transport
  of debris could cause problems in unexpected areas. The highest
  concern are north of Lake Tahoe.

* Keep an eye on recent burn areas north of Lake Tahoe including the
  Davis, Mill and Bear burns, where minor flooding is possible.
  Flooding could be exacerbated by the transport of ash, sediment,
  and debris that may obstruct drainage areas.

* Minor to moderate River flooding is possible on the Susan River at
  Susanville, and Middle Fork of the Feather Middle Fork Feather
  River near Portola, CA, with significant rises on other rivers and
  streams, most notably the Pit River near Canby and the West fork
  of the Carson near Woodfords. The West Fork Carson River and Susan
  River will respond more quickly into action stage this weekend,
  while the Middle Fork of the Feather and Pit River at Canby are
  expected to continue to rise into early to mid next week. Although
  flooding is not expected on the West Fork Carson River and the Pit
  River, the Susan River and Middle Fork Feather River are
  forecasted to crest above minor flood stages Monday and early
  Wednesday morning respectively.

* Considerable uncertainty still exists with the river forecasts
  due to variability in the rain-snow elevations, persistence of
  heavy rainfall in each watershed, dry soils, and limited low
  elevation snowpack.

* Check cnrfc.noaa.gov for updated forecasts. River forecasts will
  be updated 3 times per day during the event by 9am, 3pm, and 9pm.
  Flood impact statements are also available at cnrf.noaa.gov.
  - TB/Amanda

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 10 PM PST Saturday NVZ002.

     Flood Watch from Saturday afternoon through Tuesday afternoon
     NVZ002.

     Winter Storm Watch from late Saturday night through Monday
     evening NVZ002.

     Lake Wind Advisory until 7 PM PST Saturday NVZ002.

     High Wind Watch from Sunday morning through Sunday evening
     NVZ001-003.

CA...Winter Weather Advisory until 10 PM PST Saturday CAZ071-072.

     Flood Watch from Saturday afternoon through Tuesday afternoon
     CAZ071-072.

     Winter Storm Watch from late Saturday night through Monday
     evening CAZ071-072.

     Lake Wind Advisory until 7 PM PST Saturday CAZ072.

     High Wind Watch from Sunday morning through Sunday evening
     CAZ073.

&&