High Wind in Nevada, November 19, 2016

Area Forecast Discussion
National Weather Service Reno NV
310 AM PST Sat Nov 19 2016

.SYNOPSIS...

Moderate winter storm will impact the Sierra and western Nevada
through Sunday with winds, rain, and mountain snow. A break is
expected early next week before another weaker storm arrives
Wednesday. Storm pattern is forecast to remain active with
significant storms possible over the Thanksgiving weekend.

&&

.SHORT TERM...

Only minimal changes to the forecast tonight with a moderate winter
storm on track for today through Sunday. Slight adjustments were
made to continue to increase QPF, mostly along in the Sierra crest
in Mono County, and some increased spillover into the Carson Range
and into Western Nevada. Much of the recent increase in QPF and
spillover are due to the fact that the storm is splitting later then
previously expected. The storm still spits but not before it begins
to interact with the Sierra.

One of the greatest challenges with the current forecast, and one of
the biggest impacts is snow levels, especially around the Tahoe
Basin today. Temperatures will be conducive for snow levels to
remain around 6500-7000 feet through Sunday when colder air arrives.
However, very dry air ahead of the storm will allow snow levels to
drop by 1000 feet or so down to the wet bulb temperature. In some
areas snow levels could remain low if precipitation rates are high
enough. This would be most likely right along the Sierra crest in
places like the west shore of Lake Tahoe and potentially into
Truckee. In other areas like South Lake Tahoe southerly flow may
continue to bring enough warm air in that snow levels only drop
briefly, or not at all. In general, expect snow levels to drop down
to around 5500-6000 feet in the Sierra with the first band of
precipitation and then rise to around 6500-7000 feet as precipitation
rates decrease.

The first significant round of precipitation is expected to begin to
impact the Sierra along Donner Summit between 12-2 pm. Heavy
precipitation is expected, especially for Donner Summit and Carson
Pass through the afternoon tapering later in the evening with
limited spillover into western Nevada. Another band of heavier
precipitation is expected late Saturday night into Sunday. This will
be the best chance for precipitation to spill over into western
Nevada as divergence aloft increases as the system begins to split
and upper level forcing increase. This second wave is also when
precipitation will be pushed south into Mono County.

Winds are currently gusting to around 70 mph along the Sierra crest
and will continue to increase through early afternoon. Winds have
begun to mix down to the surface with gusts around 35 mph around the
Tahoe Basin and western Nevada. Winds are expected to continue to
increase through early afternoon until precipitation begins to
dampen them. -Zach

.LONG TERM...Tuesday through Friday...

An active weather pattern is expected for the second half of
next week, especially during the peak travel days ahead of and
following Thanksgiving Day. Anyone with travel plans on Wednesday
or Friday should pay close attention to the forecast due to
potential for winter driving conditions in the Sierra.

Ridge moves over the area on Tuesday with generally light winds
and valley inversions. Another fast-moving shortwave trough will
push into Northern CA/NV Tuesday night into Wednesday, bringing
light snow accumulations up to a few inches for the Sierra
passes. This storm doesn't look overly strong, although there
will be potential for travel delays and slick road conditions in
the Sierra above 5500 feet, especially from Highway 50 northward
on Wednesday.

Shortwave ridging looks to build in briefly for Thanksgiving Day,
bringing clearing skies and nicer fall weather for the holiday.
Winds will become a little breezy on Thanksgiving, as another storm
system approaches the region for Friday.

The next weather system moves into Northern CA/NV Thursday night
into Friday, bringing more increasing winds, mountain snow and
from rain/snow mix to the valleys. Snow levels may lower to around
5000 feet or lower on Friday morning, meaning that slow downs and
potential winter driving conditions for the Sierra and even into
some lower elevations of northeastern CA and western NV. Yet another
fast moving system could push into the northern Sierra late
Saturday into Sunday, although the latest ECMWF is keeping this
further north into WA/OR. Hoon

&&

.AVIATION...

Winds will increase over ridges this morning for increasing
turbulence east of the Sierra. Pockets of wind shear (mainly speed)
are likely in and near the Sierra this morning. It will remain
breezy with some mechanical turbulence this afternoon but shear
should diminish.

Precipitation-wise, higher elevation snow and valley rain develops
in the Sierra later today, reaching the Tahoe area in the afternoon.
This will bring widespread terrain obscuration with substantially
lowered CIGS/VIS for northern Sierra (KTRK/KTVL) terminals. The
worst period for CIGS/VIS at KTRK and KTVL looks like before sunset
this evening as a period of snow is expected during the day. By
tonight, snow levels may rise enough in the Tahoe area for some
improvement in CIGS/VIS (to above airport minimums anyway).

For lower valley terminals today, MVFR conditions likely for
northeast CA and northwest NV (north of Gerlach) as showers move
into that area. For western and west-central NV, mainly VFR
conditions are expected with just some periodic high terrain
obscurement in showers. Snyder/Hoon

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory from 1 PM this afternoon to 4 PM PST
     Sunday above 7000 feet in NVZ002.

     Wind Advisory until 1 PM PST this afternoon NVZ002.

CA...Winter Weather Advisory from 1 PM this afternoon to 4 PM PST
     Sunday above 7000 feet in CAZ072.

     Wind Advisory until 1 PM PST this afternoon CAZ072.

&&

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