Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 201712
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
912 AM PST Sat Jan 20 2018

.SYNOPSIS...Snowfall will persist into this afternoon across
Lincoln County as well as the higher elevations of Clark and
Mohave counties with light to moderate rain possible in the lower
elevations. Otherwise, breezy north winds and much cooler
temperatures are expected through the remainder of the weekend.
Dry conditions and gradually warming temperatures are expected
through the upcoming week.
&&

.UPDATE...Quick update to the forecast this morning to make
adjustments based on the latest trends and observations. Snowfall
reports are beginning to come in from the southern Great Basin.

* 0.5 in. at Mt. Charleston (town)
* 2.5-3 in. at Lee Canyon
* 3 in. around Goldfield
* 2-3 in. in Caliente
* 4 in. in Pioche
* 6 inches on Oak Springs/Caliente Summit (US-93 west of Caliente)

The brunt of the snowfall is behind us now in Esmeralda and Nye
counties, and should be winding down around mid-day in Lincoln
County.

Precipitation will continue to move east/southeast into
Clark and especially Mohave counties this afternoon, with snow
levels falling to 2500-3500 feet courtesy a dry sub-cloud layer
and low wet-bulb zero heights, especially from Las Vegas south.
This means that most of the precipitation in the valleys will at
least begin as virga, but as the layer moistens, it`s not
impossible for a few flakes to be reported in some of the higher
portions of the Las Vegas Valley (ie. Summerlin, Centennial Hills,
and Mountains Edge). Snow accumulation is not expected. For the
Spring Mountains/Sheep Range another Trace to 3 inches will be
possible with additional showers through early this afternoon.

The main concerns at this time are snow impacts across Lincoln
County, snowfall in the mountains of Clark County, and any new
accumulations in Mohave County, especially along I-40 east of
Kingman where we current estimate around of inch of snowfall. We
will continue to monitor and update as needed.
-Wolcott-
&&

.PREV DISCUSSION... /issued at 337 AM PST Sat Jan 20 2018/

.SHORT TERM...today through Monday night.

Radar returns continue to enhance across portions of the area,
including the Spring Mountains, Death Valley, central Nye and
Lincoln Counties this morning. Web cams and surface observations
have confirmed light snow showers over Spring Mountains and parts
of Nye County. This precipitation is a response to southeastward
progressing frontal boundary, which is associated with a cold low
pressure system. Low pressure will continue to progress eastward
today and will exit to the east tonight, while dragging the cold
front with it. The leading edge of the front, which is roughly
positioned along a line stretching from Ridgecrest, CA to Milford,
UT, will be a focus for precip for the next several hours.

Later today and through tonight, along with frontogenetic
forcing, upper dynamics and moisture wrapping behind the low will
put the heaviest precip over Lincoln County and northern Mohave
Counties. Snow levels have dropped to around 5000` in northern
Lincoln County and will continue to drop to around 2500` through
today, with snow amounts 4- 8" possible down to 5000` and 2-4"
above 3500`. Elevations above 5000` in the northern zones will
remain under a Winter Advisory/Warning through noon today. The
best chances for precip in Las Vegas will be primarily this
afternoon and evening, with only light showers possible in the
Valley and a few inches of more snow in the Spring mountains
(mainly above 6000`).

After the front moves through, breezy northwesterly wind will
follow in behind it. These winds should remain below advisory
level through today and begin to taper off on Sunday. Cold air
will spread across the region today/tonight as the system exits
and will bring the coldest temperature readings of the year. The
coldest night will Sunday into Monday with temperatures bottoming
out in the low to mid 30s in the LV valley.

Mostly dry, cool conditions are anticipated Sunday and Monday
with ridging building in Sunday. A very slight chance of
precipitation in the eastern Sierra crest on Monday as weak
disturbance will flatten the ridge and zip across the region.
Elsewhere, dry conditions are expected with high clouds streaming
overhead to start the week.

.LONG TERM...Tuesday through Saturday.

A progressive pattern will continue through the period and the
window of opportunity for increasing wind and chances of
precipitation will be Thursday and Friday as a broad open trough is
forecast to move across the region. This will be preceded by a ridge
centered over Nevada Tuesday which will be pushed over the Rockies
by Wednesday ahead of the incoming trough, but dry and mild
conditions will continue. The leading edge of the trough will move
across the southern Sierra Wednesday night with limited moisture
which may result in light snow amounts east of the crest. The trough
axis is forecast to traverse our forecast area Thursday and there may
be sufficient moisture for some snow showers across Nye and Lincoln
Counties, but should not be significant. The Ecmwf is less amplified
with the trough than the GFS and would keep precipitation farther
north. The PoP/WX grids are weighted more toward the ECMWF solution.
A large amplified ridge is then forecast to move in behind the trough
providing dry and mild conditions with a warming trend next weekend.
Temperatures will be a bit of a roller coaster with the ridge-trough-
ridge pattern but the swings will not be more than 3-5 degrees from
normal.
&&

.AVIATION...For McCarran...A low pressure system moving over
southern Nevada today will produce west winds early this morning
followed by northwest winds developing around 18Z and persist
through the afternoon and overnight hours with gusts generally 20-25
knots. SCT-BKN cloud bases of 7-8 Kft can be expected, but clouds
may briefly lower to 5-6 Kft in the afternoon with showers
possible in the terminal area between 20Z and 23Z. Skies will
clear early this evening as the systems pulls away to the east.

For the rest of southern Nevada, northwest Arizona and southeast
California...A low pressure system moving over southern Nevada
today will produce scattered to numerous rain showers and snow
showers with MVFR conditions over portions of southeast Nevada and
northwest Arizona near the Utah border. Elsewhere, SCT-BKN clouds
bases between 7-10 Kft can be expected. Widespread west to northwest
winds gusting 20-25 knots can be expected. The trough will move
toward the Four Corners Region this evening with clearing skies, but
gusty northwest winds persisting tonight.
&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&

$$

SHORT TERM............Boothe
LONG TERM/AVIATION....Adair

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