Heavy Snow and Winter Weather in California, March 4 to 6, 2023

Area Forecast Discussion
National Weather Service Reno NV
317 AM PST Sat Mar 4 2023

.SYNOPSIS...

A multi-day winter storm will impact the region starting today.
Heavy snowfall and strong winds in the Sierra will make travel in
the mountains impossible today into early next week. Strong winds
and snow showers are also expected into northeastern California and
western Nevada.

&&

.SHORT TERM...

Bottom line: Our next winter storm will bring major impacts to the
Sierra starting today and continuing into early next week. Impacts
from heavy snow will be amplified for those in the Sierra still
facing difficulties from extraordinary snow totals from the previous
storm. Travel in and around the Sierra is highly discouraged through
at least Monday.

A closed low originating from the Gulf of Alaska will continue to
slide south this morning before settling off the coast of the
Pacific northwest this afternoon. Ensemble members hold strong
agreement that the low will remain parked off the coast of the
Pacific northwest through Tuesday and eject a series of shortwaves
into northern California and Nevada during its residency. This
will bring several rounds of moderate-to-heavy snow, in addition
to strong winds to the region into early next week.

* WINDS: Gusty southwesterly winds have already developed along
  mountain ridgelines as a strong upper-level jet is directed over
  the Sierra ahead of the incoming low. Model guidance indicates
  ridge winds will continue to increase into this afternoon, as
  700 mb flow peaks around 60 knots. Strong winds are expected to
  mix down to valley floors later this morning. Expect a gradual
  uptick in winds as surface thermal and pressure gradients
  strengthen through the afternoon. Blended guidance indicates a
  likely (>80%) chance for widespread wind gusts of at least 50
  mph. The ECMWF EFI is highlighting western Nevada, especially
  the west-central Basin & Range, for wind gusts today. Blended
  guidance over this region suggests a likely chance (>80%) for
  wind gusts of at least 55 mph. Winds will remain elevated into
  Sunday as the upper-level jet drops southward through the
  region. However, surface winds will generally be lighter than
  today, with gusts between 30-40 mph across a majority of the
  region while winds remain strong on mountain ridges with gusts
  80-100 mph. Impacts from strong winds today and Sunday include
  areas of blowing dust across the west-central NV Basin & Range
  that may lead to low visibility along portions of I-80, US-95,
  and US-50; LLWS and turbulence; and high-profile vehicle
  restrictions.

* SNOW: The first round of snow is expected to begin in the Sierra
  late this morning (around 8-10 AM), spreading south down to Mono
  County by the early afternoon (1-2 PM). Snowfall rates of 1" per
  hour will be common in the Sierra, with a period of higher
  snowfall rates (2-3" per hour) as a heavier band pushes
  southeast through during the afternoon/early evening. Spillover
  into northeast California and western Nevada will be limited to
  light snow showers ahead of the heavier band, which will
  initiate a period of steady snowfall around 2-4 PM for major
  urban cores of western Nevada. Snowfall will become more showery
  behind this band, becoming lighter through the remainder of the
  evening. Another relatively stronger shortwave will eject off
  the main trough early Sunday morning and initiate another round
  of snow for the region. Moderate-to-heavy snow will initiate
  again in the Sierra just after midnight on Sunday, with another
  intense band rolling through with enhanced snow rates around 3
  AM. This band will once again allow efficient spillover into
  northeast California and western Nevada early Sunday morning.
  Between today and Sunday night, expect 2-4 feet of snow for the
  high Sierra, 1-2 feet for the Tahoe Basin, 6-12 inches for Mono
  County, and 2-6 inches for the Greater Reno-Carson-Minden areas.
  Additional weak waves will eject off the parent low on Monday
  and Tuesday, allowing light to locally moderate snowfall to
  continue in the Sierra.

-Whitlam

.LONG TERM...

Ensembles are coming into better agreement that the low will
weaken and eject a trough into the Great Basin on Wednesday,
which could bring additional forcing for yet another round of
snow. However, models have yet to reach a consensus on the exact
track of this system, which would dictate the amount/location of
snowfall. Regardless, if you plan to head into the Sierra on
Wednesday, keep an eye on the forecast as this could lead to an
extension of travel disruptions.

Beyond Wednesday, models continue to diverge in potential scenarios.
As such, confidence still remains low through the remainder of the
forecast period.

-Whitlam

&&

.AVIATION...

* Winds were ramping up already this morning with gusts 70 kts
  across the ridges as a 150 kt upper level jet pushed into the
  northern Sierra/western NV in advance of our next winter storm.
  This jet maxima is forecast to strengthen and peak around 180 kts
  by 12Z Sunday. Widespread moderate turbulence can be anticipated
  this weekend with bouts of severe turbulence not out of the
  question. FL100 winds 50-60 kts will result in wind gusts
  approaching 100 kts over the Sierra ridges and as high as 75 kts
  for some ridges along foothill locations. Mixing and tightening
  surface gradients will result in sustained southwest winds 15-25
  kts for area terminals through the weekend with bouts of stronger
  sustained winds ahead of a couple of shortwaves moving through the
  region. For today, gusts 30-40 kts will be common, occasionally
  approaching 40-50 kts along the Hwy 395/I-580 corridor. Blowing
  dust may reduce visibility for airports along and east of Hwy 95
  in the Basin and Range as well.

* Snow showers will spread into the Sierra this morning and become
  heavy at times this afternoon-Sunday. Significant accumulating
  snow and blowing snow will keep KTRK-KTVL-KMMH below minimums
  almost the entire time. For western NV airports, snow showers will
  spill over with most likely periods of impacts from mid afternoon
  to early evening today with a second round Sunday morning. Several
  inches of snow can be expected for Sierra Front airports (KRNO-
  KCXP-KMEV).

* The active, unsettled weather will continue through at least
  Monday-Tuesday, with periods of brisk winds and snow lending to
  unfavorable flying conditions. Some of the latest scenarios drop
  another shortwave and shot of snowfall into the region Wednesday.
  This is a new development, so we'll have to watch it.

Hohmann

&&

.AVALANCHE...

A strong winter storm will impact the Sierra starting today
through late Sunday. This is expected to bring significant snow
accumulations, strong winds, and much colder temperatures.

* Snow Water Equivalent (SWE): Near 100% probability of SWE rates
  exceeding 1"/24 hours west of Tahoe, and 80% for Mono County.
  Total SWE projections 2-3" west of Lake Tahoe, 1-2" east of Lake
  Tahoe, and 1-2" for Mono County from Saturday through Sunday
  night.

* Snowfall Rates: 1"/hour likely (>90% probability) for majority
  of the storm. 2"/hour likely (70-80% probability) overnight
  Saturday into Sunday morning.

* Snow-Liquid Ratios: High snow-liquid ratios of 16-18 to 1.

* Winds: Southwest to west ridge-top gusts 100+ mph for majority
  of Saturday-Sunday, with 50+ mph gusts at times below the ridge
  lines.

Additional rounds of light snowfall are likely (>60%) in the Lake
Tahoe area on Monday and Tuesday. Total SWE projections are
between 0.25-0.5", with lighter amounts in Mono County. Winds
during this time will remain from the southwest, but will be
considerably lighter at 40-60 mph along the ridgelines.
Temperatures will remain below average.

A recent change to the forecast includes potential for another
shortwave trough to initiate another round of snow on Wednesday,
though details remain lower confidence at this time.

-Whitlam

&&

.REV Watches/Warnings/Advisories...
NV...Wind Advisory from 7 AM this morning to 10 PM PST this evening
     NVZ001-004-005.

     Winter Storm Warning from 10 AM this morning to 4 AM PST Monday
     NVZ002.

     Wind Advisory from 7 AM this morning to 1 PM PST this afternoon
     NVZ003.

     Winter Weather Advisory from 1 PM this afternoon to 10 AM PST
     Sunday NVZ003.

CA...Wind Advisory from 7 AM this morning to 10 PM PST this evening
     CAZ070.

     Winter Storm Warning from 10 AM this morning to 4 AM PST Monday
     CAZ071.

     Winter Storm Warning from 10 AM this morning to 4 AM PST Monday
     CAZ072.

     Winter Storm Warning from 2 PM this afternoon to 4 AM PST Monday
     CAZ073.

&&