Area Forecast Discussion
Issued by NWS Reno, NV

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483
FXUS65 KREV 102258
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
258 PM PST Tue Dec 10 2019

.SYNOPSIS...
A weak weather system will sweep through overnight. It will bring
very light snow showers to the mountains this evening through
Wednesday morning, but little accumulation is expected. A
stronger weather system may impact the region by the end of the
week into the weekend with a mix of rain, snow and winds possible.

&&

.SHORT TERM...
Light winds, inversions, and poor mixing will be the story through
the remainder of the day today before a weak system pushes through
the region late tonight and early Wednesday morning.

Winds will continue to increase across the Sierra ridges overnight
as the system approaches Northern CA/NV. Sierra ridge wind gusts
are in the 30s mph range for now, but they may reach gusts
between 50 to 60 mph.

Precipitation will be light with this system with maybe a dusting of
snow across the Sierra with a very low chance of amounts measured in
inches through Wednesday morning. Primary concern with the light
rain/snow showers will be the potential for slick, icy road
conditions Wednesday morning. For the lower valleys in western
Nevada, there may be some light rain showers through early
tomorrow morning.

Sierra ridge winds will remain gusty on Wednesday and mix down to
lower valley locations on Thursday. The winds will help to promote
better ventilation and decrease the risk of air pollutants building
up in the valleys. The improved mixing will also allow the
temperatures to warm into the mid to high 50s, which is pretty warm
for this season.

Winds will ramp up noticeably early Thursday morning for the Sierra
ridges as the next waves of a storm approach. The onset of this
storm will be interesting as much of the Sierra and western Nevada
will remain on the southern (warm) side of the incoming upper level
jet. Although there is a moisture tap along with this storm, the
snow levels will be quite high initially. Plan for mainly light
rain below 7500-8000 feet for Thursday night into Friday morning.
The bigger impact with this storm, at least initially, will be the
gusty winds, with ridge wind gusts approaching 80-90 mph and
valley winds between 35 to 45 mph, with wind prone & foothills
wind gusts up to 50 mph. -Edan


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

Moist onshore flow will continue Friday into Saturday with around
an inch of QPF possible along the Sierra crest and a few light to
moderate showers in western Nevada.

For most of the event, the Sierra will be on the warm side of the
jet stream keeping snow levels relatively high to start. Cold air
is expected to eventually move in from the north, but most of the
precipitation is expected ahead of the front. Snow levels will
start around 8000 feet early Friday and drop to down to near
Nevada valley floors by Sunday. Travel impacts will be possible
for Sierra passes from Friday evening through Saturday night.
Snow accumulations are forecast to be in the 6-12" range above
7500-8000 feet. For elevations between 6000-7500 feet, rain is
expected to turn to snow on Saturday with up to a few inches
possible near Lake Tahoe level. Precipitation is going to be
mainly focused in the central Sierra with only 0.2-0.4" of QPF
down to the Mammoth area.

A secondary cold front is possible late Saturday night. This
could drive accumulating snow down to western Nevada valley
floors, which could bring some snow impacts to the lower
elevations, however this feature has lower predictability this far
out. Either way, accumulations would most likely be light.

Much cooler temperatures are expected for the start of next week
with high temperatures in the valleys only reaching the upper 30s
to low 40s Sunday into Monday.

Atmospheric River tools are showing signals of another round of
moisture impacting the region around the Dec 19th-22nd time frame.
It`s too early to forecast the strength or snow levels of this
moisture influx, but since it starts to get into Christmas travel
timeframe, it`s worth noting. If you have trans-Sierra travel
planned during that time period, keep an eye on the forecast.
-Zach


&&

.AVIATION...

A weak system moves in tonight into Wednesday bringing light snow
along with the return of lower ceilings obscuring terrain. While
the rain and breezy winds with this system may help to disperse
fog at KTRK later this evening, low visibility and ceilings may
persist due to snow showers sweeping through late tonight into Wednesday
morning. Runways in the Sierra could see a dusting of snow
tonight.

Winds across Sierra ridges are likely to peak this evening in the
50-65 kt range, leading to turbulence along and downwind of the
Sierra. -Edan

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

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



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