Winter Storm Warning 4, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
107 PM PST Fri Feb 3 2023

.SYNOPSIS...

Light Sierra snow showers and gusty ridge winds continue today. A
strong winter storm will bring more widespread wind and snow
impacts to the Sierra Saturday evening through Sunday. Some snow
impacts are possible into portions of western Nevada on Sunday as
well. Quiet weather returns for at least the first half of next
week.

&&

.DISCUSSION...

Light snowfall in the Sierra along with strong/gusty ridgetop
winds will continue into mid afternoon. As of late morning, CA
traffic cameras show little to no roadway accumulation, except for
places like Bogard. We'll still see some slick/wet roadways along
portions of I-80, US-50, and US-89 so be sure to use additional
caution if driving in the mountains today. Farther east, 15-25
degree dewpoint depressions suggest the lower layers are a little
too dry and virga is more likely to occur - as evident on radar
and visual observations from north Reno.

A second, more potent winter storm is still expected to impact
the region starting tomorrow evening. The first noticeable change
in the weather will be increasing south-southwest winds with gusts
as high as 100-120 mph along the ridges and gusty winds in the
lower elevations. At this time, Mono county has the greatest
chance for impactful wind gusts of 50-60+ mph to work its way into
population centers and major roadway arteries (US-395),
particularly late Saturday night. Elsewhere, max gusts look to be
in the 35-45 mph range with higher gusts in wind prone areas
possible.

Snowfall may begin to impact the eastern Sierra and NE California
as early as late afternoon Saturday. Latest guidance, however,
suggests higher snowfall rates will hold off until after sunset
Saturday which is when the winter-related products go into effect.
**The highest snowfall rates, and as a result the most significant
roadway impacts, look to be during the overnight hours between
10PM Saturday and 4AM Sunday.** Expect snow showers continue
through Sunday in the Sierra. EFI and other guidance continues to
suggest that there may be sufficient instability with this system
to produce isolated thunder (10-15% chance) across the immediate
Sierra crest on Sunday afternoon. The placement of the jet streak
over the eastern Sierra, which places the Tahoe Basin and western
Nevada in the left exit region, will create the forcing required
for a very convective and showery day Sunday after the surface
front passes. The best chance for accumulating snowfall into
western Nevada will be during the day Sunday as snow levels fall
near valley floor and these convective showers drop quick bursts
of moderate snowfall.

At this time, total projected snowfall accumulations look to be
between 1 to 2 feet above 7000' in the Sierra (isolated high end
totals of 3 feet along the immediate crest), 5 to 10 inches at
Lake Tahoe level, including Truckee and Markleeville. Currently,
blended guidance provides a 20-30% chance we could see 12 inches
or more around the Lake. In Lassen and eastern Sierra/Plumas
counties, up to 18 inches will be possible along the crest in the
higher elevations. However, most of the area above 5000' and west
of US-395 should see 4-10 inches and a few inches or less
elsewhere. For western Nevada, snow totals will be highly
dependent on the individual convective showers which tend to be
lower predictability. Foothills and VC should prepare for 2-4
inches with the caveat that some areas could see much more, or
less. For the valleys, an inch or less appears reasonable. Farther
east across the Basin and Range, snow accumulations will favor
the higher mountain ranges with little impacts expected to the
major roadway arteries.

Seasonal temperatures and quieter weather will return to the area
on Monday. There are rather large model discrepancies with
respect to another possible weak system on Wednesday. There is
better agreement, however, that we'll at least see active weather
return by next weekend.

-Dustin

&&

.AVIATION...

* Be prepared for gusty southwest winds, periods of turbulence,
  and LLWS across higher ridges today as locally breezy conditions
  briefly mix downward into the US-395 corridor through this
  afternoon. Higher Sierra ridges will see gusts occasionally
  exceeding 80-90kts that gradually decrease below 30kts aft 06Z
  tonight. The attendant periods of moderate turbulence and
  pockets of LLWS will also dissipate for Sierra terminals near
  US-395/I-580.

* A stronger winter storm will bring another round of CIG/VIS and
  turbulence impacts to regional terminals Saturday night and
  Sunday. Winds at FL100 will peak from the southwest 45-60kt
  during the period Sunday 03-15Z but diminish to 20-30kts through
  Sunday. Turbulence and LLWS also peak during this period for
  Sierra terminals (KTRK-KTVL). Strong surface winds are also
  possible for the foothills/valleys along US-395, especially from
  KMEV-KMMH during this period.

* Starting Saturday evening, light to moderate snow will bring
  LIFR/IFR to Sierra terminals (KTRK-KTVL). Hi-Res model guidance
  shows a chance for convective bands of snow showers that produce
  quick bursts of heavy accumulations overnight Saturday into
  Sunday. Rain/snow will spillover into western NV early Sunday
  morning and bring periods of MVFR/IFR conditions to terminals
  across the region, especially for KRNO-KCXP-KMEV. For lower
  elevation terminals with a slight chance (10-15%) of
  accumulating snow, amounts will range from a trace to less than
  an inch.

-Amanda

&&

.REV Watches/Warnings/Advisories...
NV...     Lake Wind Advisory until 7 PM PST this evening for Lake Tahoe in
     NVZ002.

     Winter Storm Warning from 7 PM Saturday to 10 PM PST Sunday
     NVZ002.

CA...Winter Weather Advisory from 7 PM Saturday to 10 PM PST Sunday
     CAZ071.

     Lake Wind Advisory until 7 PM PST this evening for Lake Tahoe in
     CAZ072.

     Winter Storm Warning from 7 PM Saturday to 10 PM PST Sunday
     CAZ072.

     Winter Storm Warning from 10 PM Saturday to 10 PM PST Sunday
     CAZ073.

&&