Lake Wind Advisory 49, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
218 PM PST Sat Dec 21 2019

.SYNOPSIS...

A storm system will continue to produce gusty winds across eastern
California and western Nevada for the remainder of this weekend,
with a period of snow on Sunday that will likely impact holiday
travel over the Sierra. Below average temperatures are expected for
the rest of this year, with some weaker storm systems possibly
producing light snow accumulations and slick roads at times.

&&

.SHORT TERM...

Mid to upper level cloud cover along with southerly winds have
increased across the Sierra and into western Nevada this afternoon
as the core of this weekend's system digs southward just off the
Californian coast.

Southerly winds will be the main story for the remainder of today
with lower valleys already gusting in the 25-35 mph range and up to
70 mph along the Sierra ridges. A Wind Advisory for the Sierra,
northeast California, and Mineral and Washoe counties is in effect
until Sunday evening when southwest winds are forecast to decrease.
During that time, expect south winds 20-30 mph with gusts up to 55
mph at times, especially for wind prone areas including the Hwy 395
corridors in Mono County, near Honey Lake, and through Washoe
Valley. Along the Sierra crest, gusts could reach up to 100 mph at
times. Rough lake conditions on Tahoe and Pyramid are anticipated.
The strongest period of winds are likely to occur Sunday morning
into the afternoon as the negatively- tilted trough and associated
upper level jet streak moves inland setting up over the eastern
Sierra and into western Nevada.

Precipitation with this system will come in two waves with the bulk
of the moisture focused on the Sierra. The first push of moisture
will likely start by Sunday morning in the Sierra and northeast
California lasting through the evening hours before the shortwave
trough lifts to the northeast. Snow levels will start out Sunday
morning just above 6000 ft before dropping to all valley floors by
nightfall. Snow accumulations will be highest along the Sierra crest
with 6 to 10 inches forecast by Monday morning with 1 to 4 inches
probable around Lake Tahoe level, including Truckee, South Lake
Tahoe, and Mammoth Lakes. Hazardous road conditions on the Sierra
passes Sunday through Monday morning are highly likely, plan
accordingly. Due to the southerly trajectory of the first wave, not
much spillover into western Nevada is expected, besides for some
light rain/snow showers here and there.

By Monday afternoon, chances for light precipitation increases
mainly for areas downstream of the secondary, more elongated trough,
including southern Mineral and Mono counties as well as for areas
east of US-95 and into eastern Nevada through Christmas Eve morning.
Snow levels at this time will remain on valley floors with up to an
inch of snow expected.

As for temperatures, this afternoon will be the warmest compared to
the rest of the weekend through next week due to the southerly,
warmer flow and strong winds providing sufficient mixing.
Thereafter, high and low temperatures will be cold with highs only
in the 30s, low 40s region-wide and lows in the teens to mid 20s.
-LaGuardia

.LONG TERM...Christmas Day through Saturday...

Some minimal changes were made to precipitation chances for the
Wednesday/Thursday time frame. The deterministic models are trending
toward a splitting system with the bulk of the precipitation staying
west of the Sierra. However...mainly ensemble members are not
displaying this splitting behavior.

The ensemble forecast members support a broader trough dropping into
the forecast area with a better chance for light precipitation over
the area Wednesday into early Thursday. The presence of this broad
trough should lead to increased lift across the area and keep
temperatures from rising to normal highs. The lows will generally
stay above average due to the presence of increased sky cover.
Moisture availability is a little limited so precipitation amounts
for Wednesday and Thursday may be a bit on the low side with less
than a foot in the Sierra. In the lower valleys of western Nevada
and northeast California any snow accumulations should be limited to
less than 1 inch. Now...all of that could change if the upper trough
does split. We would see far less precipitation.

A few snow showers linger into early Friday in the southern Sierra
and near the Oregon border. Ridging develops by late Friday into
Saturday with dry conditions. By late Friday we should start to see
valley inversions again. This will create poor mixing conditions for
early next weekend that may also help trap pollutants in the
populated valleys.

&&

.AVIATION...

Surface winds have starting increasing from the south this afternoon
in those valley areas that favor southerly winds. Gusts in the 25-35
kt range are likely into the early evening before a decrease in wind
speeds. Winds will begin to increase again Sunday and shift to a
more southwest to west direction through the day.

Numerous reports of turbulence and low level wind shear have been
received during descent into and climb out of KRNO today. This is
mostly due to winds veering to the south-southwest above the
surface. This is likely to continue into the overnight hours. Some
low level wind shear is possible Sunday as well. Stronger winds
aloft will almost guarantee continued bouts of light to moderate
turbulence above and east of the Sierra.

By midday Sunday a broad upper level trough should bring snow to the
Sierra and parts of northeast California. This system is showing
signs of splitting as it moves into the region so areas east of the
Sierra may not see much snow or rain. Accumulations at the Sierra
terminals could range from 2-5 inches for KTRK/KTVL to 3-6 inches
for KMMH.

&&

.REV Watches/Warnings/Advisories...
NV...Wind Advisory until 4 PM PST Sunday NVZ001-003-005.

     Wind Advisory until 4 PM PST Sunday NVZ002.

     Lake Wind Advisory from 7 AM to 4 PM PST Sunday for Pyramid Lake
     in NVZ004.

CA...Wind Advisory until 4 PM PST Sunday CAZ070-071-073.

     Wind Advisory until 4 PM PST Sunday CAZ072.

&&

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