Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 212135

Area Forecast Discussion
National Weather Service Reno NV
135 PM PST Sun Jan 21 2018


A weak disturbance will bring very light snow for parts of
eastern California tonight and early Monday. A stronger and
colder storm is expected late Wednesday into Thursday, bringing
more snow to the Sierra and possibly to lower elevations. Expect
some travel impacts with the midweek system.



While focus remains on the more potent system that will impact the
region by midweek, there is a weak, open wave that will move
through tonight and early Monday. Radar shows a decent amount of
moisture moving onshore in northern California at this time.
However, upper level dynamics weaken significantly by this evening
with jet energy exiting well north of the surface boundary.

Still, there will be sufficient moisture for some token snow
accumulation in the Sierra. Up to 2 inches can be expected below
7000 ft from western Lassen County through the Tahoe Basin. Up to
4 inches are possible above 7000 feet in and adjacent to the Tahoe
Basin. This wave will lose more of its already weak punch the
farther south it moves, leaving Mono County only with up to a
inch or so above 8000 feet. There is very little to no
precipitation expected for western Nevada south of a Susanville to
Gerlach line. The Surprise Valley and northern Washoe County could
see around an inch of accumulation tonight.

Conditions become drier Monday under zonal upper flow. A few
lingering showers in Western Lassen and central Plumas Counties
will be possible, but overall precipitation chances will become
nil through Tuesday. Winds begin to increase Tuesday night ahead
of the next, more significant system with a few showers possible
for western Lassen County heading into Wednesday morning. Boyd

.LONG TERM...Wednesday through Sunday...

The midweek system continues to come together as a relative strong
system with a decent moisture tap. The deterministic models are in
general agreement...although the ECMWF is still a bit faster pushing
the initial precipitation into the forecast area when compared to
the NAM and GFS.

The integrated vapor transport tools continue to show better chances
for a moderate moisture feed in place for about 12 hours traversing
from north to south through northeast California and the Sierra from
Wednesday evening through Thursday morning. This appears to be the
best time for accumulating precipitation/snow in the forecast area.

This is still a fast moving it is not expected to
produce the large amounts of precipitation more common to deep...
cold Sierra storms. Given the solutions are a bit more consistent...
we have opted to increase the forecast precipitation a little more
and lower snow levels a bit at the start of the precipitation. This
could lead to accumulations as high as 10-18 inches above 7000 feet
in the northern Sierra...possibly as high as 2 feet near the
crest...with 6 to 12 inches around Tahoe and in much of Mono County.
Accumulations are likely to be a little lower for the western
portions of Lassen County and central Plumas County. East of the
Sierra...amounts will be far less...but there is a possibility of a
few inches in the lower valleys given the colder start to the storm.

The models continue to increase the wind field associated with the
system. While not sustained for a long period of time...we should
see gusts in the 45-50 mph range during the day Wednesday.

For now we will hold off on any watches for the system and let the
details come into focus a little tonight and early Monday.

Snow showers linger into early Friday morning before the main trough
moves east. A ridge tries to develop for the weekend...but there
remains a minor piece of energy that rides over the ridge Saturday
resulting in a possibility of weak warm air advection precipitation
near the Oregon border.



High clouds have moved in today ahead of a weak system that will
move across northern CA and northern NV tonight and Monday.
Precipitation will be sparse although a few snow showers mainly
north of I-80 could reach the Tahoe Basin and bring brief periods
of MVFR cigs/vsby as well as mountain obscurations in light snow
00Z to 18Z Monday. Accumulation on runways at KTRK/KTVL will be
less than 2 inches. While a few flurries are possible at
KRNO/KCXP, accumulation is very unlikely.

Winds will increase across the ridges later today through early
Monday with gusts around 50-55 kts. Surface winds will generally
remain light although the gradient will be a bit stronger across
northeast CA and northwest NV, generally north of KSVE-KWMC where
some gusts this afternoon/evening could reach 30 kts.

More significant weather will return by the middle of the week
with gusty winds, widespread strong turbulence, and chances for
snow area-wide. Hohmann/Boyd


.REV Watches/Warnings/Advisories...


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