Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 201250
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
450 AM PST Fri Jan 20 2017

.UPDATE...

Decided to expand the Winter Storm Watch for Sunday into the
western Nevada basin and range in addition to the Surprise Valley
in California. Please see the statement for expected totals and
impacts. -Dawn

&&

.PREVIOUS DISCUSSION... /Issued 356 AM PST Fri Jan 20 2017/

SYNOPSIS...

The second in a series of three storms will impact the Sierra and
western Nevada today. The third storm will be a major winter
storm which will impact the region Saturday night into Sunday.
Significant winter weather driving slow downs will continue in the
Sierra and western Nevada into next week. Much drier weather is
expected for the middle of next week.

MAIN WEATHER CONCERNS THIS WEEKEND:

*Second in a series of three winter storms impacts the region today
into Saturday morning.

*Lull in the weather Saturday afternoon is your window of
opportunity to make preparations for the next storm.

*Powerful Winter Storm to impact the Sierra AND western Nevada
Sunday into Monday.

*Below are some of the concerns, impacts, and preparation measures
you can take for the Sun-Mon storm from yesterday`s discussion.

 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.

SHORT TERM...

The main push of snowfall is beginning to impact the Sierra early
this morning across the Sierra. Expect deteriorating driving
conditions through the Sierra this morning with chain controls
already in effect for all open Sierra passes. This next round of
snowfall will provide another 1 to 2 feet across the Sierra through
Saturday morning with the heaviest snowfall roughly from 6am to 6pm
before lightening up somewhat this evening into Saturday afternoon.
Not expecting snowfall to completely stop on Saturday between storms
but most likely will be a continuous period of light to moderate
snowfall through the weekend until the next and stronger storm
arrives Saturday night into Sunday (See the Long Term discussion for
details on this storm).

Across western Nevada the main spillover of snowfall looks to occur
after 7am this morning with periodic bands of spillover snowfall
occurring through the afternoon with snow showers lightening by this
evening with a break through Saturday afternoon. Looking at about 2
inches for the valley floors with higher accumulations heading south
through Washoe Valley, Carson Valley, and Virginia City where 3-6"
will be possible. Other outlying foothill areas will generally
see amounts in the 1-4" range. Fuentes

LONG TERM...Saturday Evening through Friday...

* Blizzard conditions likely in the Sierra on Sunday.
* Sunday could be one of the heaviest snow events western Nevada has
  seen in years.
* Be prepared for extreme travel delays and potential road closures
  and power outages.

The strongest of the three storms this week is still slated to move
into the region late Saturday night, continuing to impact the region
through Monday night. The heaviest precipitation is anticipated on
Sunday which in conjunction with strong winds is likely to create
blizzard conditions in the Sierra. This is also shaping up to
potentially be one of the heaviest snow events western Nevada has
seen in years. Significant travel impacts are likely Saturday night
through Monday morning, with lesser impacts lasting into Monday
night as the snow turns to lighter showers.

A strong westerly 150+ kt jet is positioned across the Sierra into
western Nevada on Sunday with the first push of precipitation
associated with this storm. This will help with both upslope
enhancement into the Sierra in addition to spillover into western
Nevada. The second enhancement to the storm will come Sunday night
as a surface front and vorticity maximum interact and once again
increase snowfall rates. Instability showers will then continue
Monday, tapering off Monday night.

There is warming aloft present in soundings as the first portion of
this system moves into the region, however, these profiles are
staying below freezing at all levels. Have allowed a rain/snow mix
in the lowest valleys Sunday morning to account for this warm
layer, but feel the more likely scenario will be a period of
heavy, wet snow. As the colder air filters in Sunday, snow ratios
will increase with the character of the snow becoming more
powdery.

The main change to the forecast was to continue the trend of
increasing liquid precipitation totals and therefore snow amounts
for this storm, especially on Sunday. Snowfall rates in the Sierra
could exceed 2-4" an hour during the peak of the storm with white
out conditions due to heavy snow and blowing snow. Current
expectations are 3 to 4 feet of additional snow in the high Sierra
with 12 to 30 inches in the Tahoe Basin and for communities along
Highway 395 in Mono County. Into western Nevada, totals through
the Greater Reno/Sparks/Carson City areas could reach 6 to 14
inches on valley floors with 1 to 2 feet in foothill locations,
including the Virginia City Highlands. Farther east across western
Nevada, 3 to 8 inches of snow is possible.

Road closures and power outages are possible, especially in the
Sierra, so be sure to prepare during the relatively quiet period on
Saturday. If you have snow on your roof, carport, deck, etc take the
time to clear it off because additional heavy snow will continue and
structures could fail under the weight. The other concern will be
the chance for trees to fall. Many trees are damaged from the past
drought, then have had loads of snow piled on top. In addition, the
ground is saturated, so the strong winds will easily be able to
damage if not topple weak trees.

Tuesday through Friday conditions will be dry with a ridge building
across the west. With the anticipated snow on the ground, this will
lead to strong inversions developing through the week and poor
mixing. We will have to see if the inversion also leads to areas
with fog and low stratus, but will leave out of the forecast for
now until we see how the storm Sunday plays out. -Dawn

AVIATION...

Another winter storm is pushing into the Sierra and western Nevada
this morning bringing widespread terrain obscuration and reductions
to cigs/vis in snow throughout the day. In the Sierra, KTRK, KTVL,
and KMMH could see 5 to 8 inches of accumulation by sunset tonight,
with an additional 5 to 10 inches overnight and through the day
Saturday.

Into western Nevada, for KRNO and KCXP, the worst conditions today
will likely be between 5 and 10 am, with showers continuing
thereafter. By sunset, 1 to 4 inches of accumulation are possible on
runways. Farther east, up to 1 inches is possible for KLOL/KNFL.

Snow will continue in the Sierra tonight into Saturday, while
western Nevada will be fairly precipitation free. However, mountains
will still be obscured due to clouds.

The next major winter storm will push into the region Saturday night
into Sunday with impacts lasting into Monday. Please see the long
term section for additional details and snow accumulation potential.
-Dawn

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 10 PM PST this evening NVZ005.

     Winter Storm Watch from Saturday evening through late Sunday
     night NVZ005.

     Winter Storm Warning until 4 AM PST Monday NVZ002.

     Winter Storm Watch from late Saturday night through late Sunday
     night NVZ001-004.

     Winter Weather Advisory until 10 PM PST this evening NVZ003.

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

CA...Winter Storm Warning until 4 AM PST Monday CAZ071.

     Winter Weather Advisory until 10 PM PST this evening CAZ070.

     Winter Storm Watch from Saturday evening through late Sunday
     night CAZ070.

     Winter Storm Warning until 4 AM PST Monday CAZ073.

     Winter Storm Warning until 4 AM PST Monday CAZ072.

&&

$$

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



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