Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 191107
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
307 AM PST Fri Jan 19 2018

.SYNOPSIS...

Snow will diminish today as a winter storm system exits the
region, but bands of snow showers will develop through this
evening, producing patchy slick road conditions. After a dry and
cool Saturday, weak low pressure will bring light snow late Sunday
into Monday, with a stronger cold storm possible by midweek.

&&

.SHORT TERM...

The main snow band continues to affect the Tahoe basin and parts
of northeast CA, with area web cameras showing at least a few
inches of accumulated snow on I-80 between Truckee and Blue
Canyon, and widespread chain controls across the Sierra and
northeast CA. This snow band is working its way south across
Alpine and Mono counties while for lower elevations, patchy light
rain continues with snow levels roughly in the 5000-5500 foot
range. We will retain the winter weather headlines for now, as
travel impacts will continue through the morning commute even as
snowfall rates decrease.

By daybreak, cooler air will seep in and push snow levels below
5000 feet as precip winds down, although the lower valleys will
likely be spared from a full changeover to snow. For the morning
commute around Reno-Carson City, roads will mainly be wet except
for patchy slick spots near and above 5000 feet, while around
Virginia City snowfall amounting to a couple of inches are
expected.

For this afternoon and evening, upper level trough passage will
produce some instability across northern CA along with upslope
flow across the Sierra, leading to favorable conditions for
development of snow shower bands. The best potential for these
bands will exist from western Lassen County southward along the
northern Sierra to I-80 and US-50, which could receive heavy
snowfall rates of 1-2 inches per hour at times. While most areas
are unlikely to see these bands last for longer than an hour or
so, there is always a possibility for a few locations receiving
heavier snow totals due to a band persisting for a longer time.
Some of these snow bands could extend into the urban areas around
Reno-Carson City and produce slick conditions with reduced
visibility during the afternoon-evening commute. In addition, some
lake enhanced snow bands could extend southeast of Pyramid Lake
during the late afternoon and evening as colder air aloft moves
overhead.

For the remainder of tonight through Saturday, generally dry
conditions are expected as shortwave ridge moves overhead, with
temperatures a few degrees below average and areas of mid-high
clouds especially north of I-80.

For Sunday-Monday, the next weather system looks to be relatively
weak with limited snowfall potential. Although a Pacific moisture
feed is anticipated, forcing will be weak with warm advection
aloft being the primary mechanism for producing precipitation
which will be light in intensity especially across western NV.
Currently we are projecting snowfall up to 3 inches for northeast
CA, the Tahoe basin and western Mono County, with up to 6 inches
near the Sierra crest west of Tahoe northward across higher
terrain of central Plumas/Sierra counties and southwest Lassen
county. Very light and sparse snow amounts are possible into
western NV early Monday morning, but the modest snowfall rates may
not be sufficient to produce notable accumulations on paved
surfaces. MJD


.LONG TERM...Monday night through Friday...

A general break is expected Monday night and Tuesday before the next
system arrives late Tuesday night and Wednesday. Some simulations
show a period of light warm air advection precipitation (mainly
snow) ahead of the system across northeast California and northwest
Nevada on Tuesday. By Wednesday, there is growing consensus for our
next significant storm, although there is still quite a range of
differences in the details depending on how much moisture gets
tapped. Some scenarios point to a colder more typical mid winter
storm while others tap abundant moisture and bring snow levels up
above the lower valley floors. Right now, either solution would keep
precipitation in the form of snow for the Sierra. The system is
progressive and this will be a limiting factor to the precipitation
totals. Still, the Sierra could see some decent snowfall. Colder
conditions are likely behind this system for Thursday and Friday
with temperatures below normal. Hohmann

&&

.AVIATION...

Snow will gradually wind down in the Tahoe Basin early this morning
but continue into early afternoon across Mono County as the front
works southeast. MVFR/occasional IFR conditions are expected to
obscure terrain until the snow tapers, then low clouds may linger
for a while longer after the main snowfall ends. Accumulating
snow has occurred at Tahoe area runways and will likely occur at
KMMH as well this morning.

As the trough moves across the area today, the airmass will remain
unstable for isolated-scattered snow showers. Some of the higher
resolution models continue to show snow showers developing across
the northern Sierra into the Sierra Front later this afternoon and
these snow showers could put down some brief light accumulations 23Z-
03Z. Winds will be lighter today as the cold front and associated
gradient/strong upper level winds shift south into southern NV.
Hohmann

&&


.REV Watches/Warnings/Advisories...
NV...Winter Storm Warning until 4 PM PST this afternoon NVZ002.

CA...Winter Weather Advisory until 10 AM PST this morning CAZ071.

     Winter Weather Advisory until 10 AM PST this morning CAZ073.

     Winter Storm Warning until 4 PM PST this afternoon CAZ072.

&&

$$

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



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