Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 222255
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
252 PM PST Sun Jan 22 2017

.SYNOPSIS...A strong low pressure system will bring widespread rain
and snow to the region along with areas of strong winds through
Monday. Most mountainous areas will receive significant snowfall.
There is the potential for a few thunderstorms as well Monday.
Drier, cool and locally breezy conditions are then in store for
Tuesday and beyond.
&&

.SHORT TERM...through Monday night

Conveyor belt of moisture progged to continue sliding east across
southern California, southern Nevada and northwest Arizona the rest
of today and tonight. Challenge so far today has been determining
the snow levels. Models showed warm air aloft trying to sneak in
from the south but based on observations/webcams snow levels in
southern Nevada look to be around 4000-4500 feet, southern Mohave
County looks to be around 6500 feet. So far just a little snow with
no accumulation reported on Interstate 15 at Mountain Pass.

Late tonight through Monday much colder air aloft rolls in under
core of the upper trough. Nature of the precipitation turns more
convective or showery. Models showing a decent amount of
CAPE/instability tomorrow afternoon so included a mention of
thunderstorms. Snow levels lowering as low as 3500 feet in the lower
deserts; potentially as low as 3000 feet under stronger convection.

Winds have been hit and miss today but once the steady light
precipitation starts to wind down and as the colder air arrives I
would expect some of those stronger winds aloft to finally mix to
the surface.

Regarding our headlines. The only addition was to include a Winter
Weather Advisory through Monday for elevations above 5000 feet in
southern Mohave County.

.LONG TERM...Tuesday through Saturday.

Still expecting much quieter weather in the long term.  The extended
range starts out on Tuesday under the influence of a broad upper
level trough across the Western States, keeping our region cool and
unsettled but generally dry. The cool air aloft will support a few
instability driven snow showers mainly over the higher terrain, but
given the overall dryness of the airmass very little accumulations
are expected.  The troughing will shift east on Wednesday but the
airmass will remain cool under a cyclonic northwest flow through the
end of the week.  Temperatures will average 8-12 degrees below
normal through Friday, and potentially colder in areas where there
is fresh snow cover. Clear and cool nights will also favor strong
radiational cooling, allowing snow covered areas to get quite cold
overnight.

Ridging will build in over the weekend allowing for a cool and dry
northerly flow to take over our region with rising heights. This
will allow temperatures to creep back towards normal territory,
while also inducing northerly winds down the Colorado River Valley.
&&

.AVIATION...For McCarran...Clear skies early this evening then
increasing clouds overnight. West to occasional northwest winds will
persist into this evening then are expected to settle in a light
southwest to west direction overnight. High clouds will fill in this
evening then lower overnight with cigs by morning expected to be
around 8-10k feet. Cigs will continue to lower through 15z as
precipitation moves into the region. Cigs will continue to lower
after 15z with precipitation moving into the area. Widespread rain
and cigs down to 4-5k feet expected through much of the day after
16z. Visibility could also be impacted through the day and mountain
peaks will be obscured. Winds will be south 10-20 kts.

For the rest of southern Nevada...northwest Arizona...and southeast
California...Winds will gradually decrease over western San
Bernardino County this evening. Clouds will gradually increase and
lower overnight as the next storm system moves into the area.
Lower cigs and widespread precipitation will impact the Sierra and
Owens Valley around sunrise and then spread east during the day with
cigs down to 3-5k feet with impacts to visibility possible. Most
mountain peaks will see obscurations. Winds will increase from the
south with most areas seeing speeds in the 10-25 kts range. &&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
rain or snow amounts through Monday as a storm moves through the
region.
&&

$$

Short Term...Pierce
Long Term...Outler
Aviation...Gorelow

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