Avalanche and Heavy Snow in California, January 19 to 24, 2017

Area Forecast Discussion
National Weather Service Reno NV
219 PM PST Thu Jan 19 2017

.SYNOPSIS...

Two more storms are expected through the weekend. One Friday into
Saturday morning and a much stronger one Saturday night into
Sunday. Significant winter weather driving slow downs will
continue in the Sierra into next week with some slow downs across
western Nevada valleys by the Friday morning commute. Much drier
weather is expected for the middle of next week.

&&

.IMPACTS FROM THE WINTER STORM...

Bottom line: A powerful storm will affect the Sierra through
Monday with multiple feet of snow likely. Gusty winds at times,
especially Saturday night and Sunday will create areas of blizzard
conditions in the Eastern Sierra with downed trees and powerlines
likely.

Several inches of snow are possible for many Western NV valley
floors Friday morning and especially Sunday. A couple feet or more
of snow is likely for Virginia City and the foothills of Reno and
Carson City. North of I-80, amounts do not look as extreme, but
communities along Highway 89 north of Truckee to Lassen Park will
also see significant snows of a couple feet or more.

WHAT CAN YOU DO:

* * For communities in the higher terrain: Tahoe Basin, Mono
  County (looking at you Mammoth), and Virginia City. While there
  is potential for some unanticipated impacts, such as deck, roof,
  or carport collapses, local officials are extremely concerned
  about more downed trees across powerlines, roadways, and into
  homes. Dig out and clear as much snow as possible before the
  next storm moves into the area. Snow removal will become
  extremely difficult as feet of snow piles up. Prepare for
  extended periods of power outages, more downed trees, as well as
  being stuck in your residence. Local authorities are
  recommending enough non-perishable food for up to a week.
  Listen closely to local law enforcement and fire officials for
  recommendations.

Today and Saturday afternoon will be your windows of opportunity
to dig out, stock up on supplies, and prepare for snow impacts.
Road travel disruptions due to snow, low visibility will be
possible from Friday through Monday. Long lasting road closures
due to accidents, downed trees, or snow removal operations will be
possible into Monday as well. -Edan/Wallmann

.SHORT TERM...

Snow showers continue in the Sierra at this time with some locally
heavy dropping up to 2 inches of snow in an hour. Lighter snow
showers have drifted over into Western NV. This will continue
through this evening with the showers gradually becoming less
numerous and not as intense. A few inches remain possible in
persistent bands.

The next storm moves in late tonight and will continue into
Saturday. For the Sierra and NE California, periods of snow, heavy
at times, will continue into Saturday. The most intense period of
snow is expected during the day Friday where snowfall rates could
approach 2 inches per hour in the heaviest bands. Up to 3 feet of
additional snow is possible above 7000 feet through Saturday
afternoon with 1-2 feet at lake level. A few inches on highway 395
in Mono County and to 395 in Lassen County are possible as well.

In Western Nevada, the main period of snowfall will occur tomorrow
morning into early afternoon and be focused near and south of
Highway 50. The morning commute will be impacted for the Sierra
Front and possibly the afternoon, especially in Douglas County.
The rest of Western NV will see lighter snows which will mix with
rain on the lowest valleys. A bit more of a break with occasional
snow showers Friday night into Saturday. However, Douglas County
into Carson and Virginia City will see more frequent showers with
light accumulations. Then, it gets serious for late Saturday night
through Sunday night...Wallmann

.LONG TERM...Saturday Evening through Thursday...

Forecast remains on track for the strongest of the three storms to
impact the region starting late Saturday night and continuing into
Tuesday. Snow amounts were increased with latest model simulations
and forecaster confidence is increasing for a potentially
significant snow event for the Sierra as well as western Nevada.

Latest simulations are still on track with a strong cold winter
storm moving into the region late Saturday night through early
Monday. Gusty winds are likely ahead of the system Saturday
afternoon and evening for much of the area with the strongest
winds in the Sierra and just east of the Sierra into the valleys
of northeast California and western Nevada. Sierra ridge wind
gusts from Tahoe south into Mono county will be in the 100+MPH
category, with some gusts up to 140 MPH possible.

The 150+kt upper level jet responsible for ushering in this winter
storm will move right over the Tahoe basin and tie in with a
moisture plume off of the Pacific. Very cold temperatures with this
moisture will result in relatively high snow ratios for all
elevations in the Sierra and western Nevada. The only exception will
be out across Pershing and Churchill counties where we could see
rain or a rain/snow mix. There will be two distinct bursts of
precipitation impacting the region. The first burst will be late
Saturday night with intense snowfall rates for the entire Sierra
Nevada. Then another burst develops Sunday evening associated with a
secondary vorticity lobe and surface cold front. This secondary
burst will result in spillover into western Nevada and if models
continue to hold in the pattern we could see in excess of 6
inches of snow on the valley floors west of Highway 95 through
Monday morning along with up to 3 feet in the higher elevations of
the Sierra and near 2 feet around Lake Tahoe and near Mammoth
Lakes. Winter storm warnings are in effect for the Sierra from
Lassen county southward into Mono county. We have a winter storm
watch in effect for far western Nevada, although this may need to
be expanded by future shifts.

Snow showers linger into Monday afternoon and even into early
Tuesday morning. Some model simulations are hinting at a slider
system just behind this big storm, but this is a relatively new
development in the models so we aren't incorporating that into the
forecast as of yet. A ridge slowly builds over the region by midweek
which would result in strong valley inversions, well below average
temperatures and poor air quality through the middle of the week.
- Edan

&&

.AVIATION...

A trough axis will be moving into western Nevada late this
afternoon. After a burst with the trough axis, snow showers in the
Sierra should lessen in coverage and intensity for awhile overnight.
Elsewhere across northeast California and western Nevada through
midnight, VFR conditions are expected with isolated higher terrain
obscuration possible due to brief -SHSN.

After midnight/early Friday morning, the next system will approach
the northern California coast and ramp Sierra and northeast
California snow up once again. For the northern Sierra, widespread
terrain obscuration and much reduced VIS with -SN/SN will persist
through Friday...with 5 to 8" of snowfall likely by sunset for
KTVL/KTRK terminals. Out into western NV, Friday morning will bring
the worst CIGS/VIS and terrain obscuration as a period of -SN moves
through...with between 0.5" and 2" of accumulations expected for
KRNO/KCXP/KMEV/KRTS...and up to 1" possible for KLOL/KNFL. Also,
expect widespread MVFR CIGS and IFR VIS in western NV Friday
morning, especially near and north of Highway 50.

In general, conditions will improve substantially east of the Sierra
for Friday afternoon as widespread -SN breaks up into -SHSN, or
possibly -SHRASN below about 4500 feet. However, areas of higher
terrain obscuration will continue with scattered to numerous (near
Sierra) -SHSN bringing some brief but drastic reductions in VIS. As
far as snowfall accumulations in the lower elevations after about 10
AM-noon, temperatures should warm sufficiently to heat roads/tarmacs
well above freezing for mainly wet paved surfaces. -Snyder

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory from 4 AM to 10 PM PST Friday NVZ005.

     Winter Storm Warning until 4 AM PST Monday NVZ002.

     Winter Weather Advisory from 4 AM to 10 PM PST Friday NVZ003.

     Winter Storm Watch from Saturday evening through late Sunday
     night NVZ003.

CA...Winter Storm Warning from 4 AM Friday to 4 AM PST Monday CAZ071.

     Winter Weather Advisory from 4 AM to 10 PM PST Friday CAZ070.

     Winter Storm Warning until 4 AM PST Monday CAZ073.

     Winter Storm Warning until 4 AM PST Monday CAZ072.

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For more information from the National Weather Service visit...
http://weather.gov/reno