Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 162329

Area Forecast Discussion
National Weather Service Reno NV
329 PM PST Tue Jan 16 2018


A strong winter storm will impact the region for the end of the
week. Strong winds will develop Thursday with a period of heavy
snowfall in the mountains late Thursday afternoon through early
Friday morning. There is even a potential for snow down to all
valley floors by Friday morning. Blowing snow and poor visibility
will accompany snowfall.


.Short Term...

Generally mild weather today and Wednesday with cloudy skies and
above average high temperatures. All that is about to change
starting early Thursday morning as a strong Pacific storm brings
strong winds and moderate to heavy snow to the region through
Friday. This storm has the best chance of bringing low to mid
elevation mountain snow we have seen so far this season with a
good combination of available moisture and cold air. While the
system has a decent moisture tap and strong jet forcing on the
positive side, it is also going to move through the region quite
quickly, which may limit the overall precipitation totals and how
long the strong winds may last. Cold and unstable air after the
front should allow for snow showers to continue through Friday
afternoon in the Sierra with additional snow accumulation probable
during the day.

A strong cold front will move through the region allowing the
largest pool of cold air to move over the region so far this
`winter`. Confidence is high in strong winds, low snow levels, and
a period (6-9 hrs) of moderate to heavy mountain snowfall.
Confidence is lower for snow accumulation amounts and timing in
western Nevada valleys. There is a chance that low elevation
snowfall could create hazardous travel conditions in the
Reno/Carson metro areas overnight Thursday into Friday morning.
There will likely be a burst of snow in western Nevada along the
front, but much of the accumulating snow, if it occurs, could be
from smaller scale convective showers behind the front which are
very hard to predict. A probable scenario would be 1/2 to 1 inch
of snow in the lowest valleys along the front with additional
showers during the day bringing sporadic accumulations to the
valleys. Remember, if that 1/2" comes near commute time, it can
still cause significant travel issues.

Winds pick up early Thursday morning ahead of the cold front as
700 mb flow increases to 50-60 kts. Forecast soundings show a
solid temperature inversion around ridgetop level which should
create a few hours of intense downslope winds in western Nevada
valleys. The strongest winds will most likely only last 6-8 hours
since the cold front moves through the region quickly. A High Wind
Watch has been issued for Mono County and portions of western
Nevada Thursday with winds at the surface up to 50-60 mph and up
to 80 mph in wind prone locations.

The combination of strong winds, and cold low density snow, will
create periods of low visibility, especially over Sierra passes.
This is something we haven`t experienced this winter, so be
prepared for challenging driving conditions with low visibility.

.LONG TERM...Saturday through Tuesday...

Saturday through early Sunday will be a break between weather
events as high pressure briefly moves overhead. Temperatures will
be near or slightly below average.

Sunday into Monday the next wave will move into the Northwest
CONUS, bringing increased winds, mountain snow, and valley rain
and snow. Simulations are trending more progressive with less cold
air intrusion. If simulations stay on this trend, it would mean
higher snow levels with mostly rain for the lower valleys, or at
least a period of snow changing quickly over to rain. However, a
more progressive flow would also bring the potential for much
higher precipitation totals as a more solid Pacific moisture
tap/AR plume would then impact the region. As far as the Sierra
snowpack, snow levels even in the wetter scenarios are not high
enough to preclude hefty snowfall totals in the Sierra, at least
above about 6500 feet. Details are nebulous with the recent swing
to warmer and wetter so stay tuned for clarification.

Beyond the forecast period into mid to late next week, model
simulations go off the rails as the EC builds a ridge over the far
eastern Pacific while the GFS keeps the door open for additional
systems. The EC would be drier and colder with possible slider-
type systems for northeast CA and western NV. Forecaster
confidence is abysmal at this time so we will have to wait and see
which way the pattern trends. -Snyder



A ridge of high pressure will build over northeast CA and western
NV tonight and Wednesday, bringing precipitation-free conditions
although plenty of mid to high clouds could persist. Turbulence
looks generally low (near and below ridges) with modest winds over
ridges and mainly light flow near the surface. Patchy fog is
possible near KTRK, although chance are fairly low (20%) if clouds
persist through Wednesday morning.

A strong cold front will move into the region Thursday into
Friday. Thursday`s winds will be quite strong, especially within
about 6 hours of FROPA, with wind gusts at area terminals 35-50
kts, causing low-level wind shear and moderate to severe mountain
wave turbulence over and downwind of the Sierra. This storm will
also bring snow or rain quickly changing to snow to the region
Thursday night into Friday, along with at least periodic MVFR/IFR
CIG/VIS to area terminals. A light accumulation (up to an inch) is
possible for western NV terminals. -Snyder


.REV Watches/Warnings/Advisories...
NV...Winter Storm Watch from Thursday afternoon through Friday
     afternoon NVZ002.

     High Wind Watch from Thursday afternoon through late Thursday
     night NVZ001.

     High Wind Watch from Thursday morning through Thursday evening

CA...Winter Storm Watch from Thursday afternoon through Friday
     afternoon CAZ071-072.

     High Wind Watch from Thursday afternoon through late Thursday
     night CAZ073.



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