Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 171124

Area Forecast Discussion
National Weather Service Las Vegas NV
324 AM PST Tue Jan 17 2017

.SYNOPSIS...Tranquil weather is expected through mid-week before the
next series of storm systems begins to impact the region Wednesday
evening. The first of these storms will spread rain and mountain
snow across most of the region late Wednesday through Thursday.
Additional storm systems will keep active weather going well into
next week.

.SHORT TERM...Today through Thursday night.

Very little in the way of sensible weather is expected through mid-
day Wednesday. Temperatures will continue to run just under
seasonal norms with mostly clear skies as a short wave ridge holds
over the region.

By late Wednesday the next series of storms begins to impact the
region...with gusty winds developing across the Sierra and
precipitation spreading in from the west. The track and dynamics
with this system are somewhat different from many of the other
recent storm systems that have rolled through the region recently.
The main difference is the track of the moisture plume with respect
to the terrain. Models indicate a the orientation of the moisture
plume will be SSW to NNE as opposed to a more WSW to ENE orientation
of the other atmospheric rivers we`ve seen recently. Therefore,
despite the somewhat lower moisture levels overall, the track seems
better suited to bring decent precipitation to the Mojave Desert
regions (including Las Vegas) due to a weaker terrain shadowing
effect. Therefore, I have boosted PoPs and QPF for this first storm
system, especially across the desert regions.

The two main concerns with this system will be desert rain and
mountain snow. For now, rainfall totals do not look to warrant much
concern for flooding outside perhaps some embedded convection
Thursday. Snowfall is the bigger concern, prompting the issuance of
Winter Weather Advisories for the Sierra, White Mountain, Spring
Mountain, Sheep Range, and Lincoln County all above 5000 feet. Snow
levels will begin around 8000 feet as snow begins Wednesday night,
then quickly fall to around 5000 feet by Thursday morning (perhaps
even lower over the southern Great Basin). Please see the Winter
Weather Advisory product for additional snowfall details.

Precipitation will taper off from west to east Thursday/Thursday
Night, but the break will be short-lived as the next wet system

.LONG TERM...Friday through Monday night.

The second in a series of troughs will impact the area by Friday
afternoon. With a decent moisture tap and favorable moisture
trajectory, confidence a little higher in heavier precipitation
compared to the previous system, with duration likely the limiting
factor for amounts. Potential for heavier rain amounts in portions
of San Bernardino and Mohave counties will need to be monitored, as
the GFS signals a more significant event there. Snow levels will be
in the 4000ft to 5000ft range.

After a brief break on Saturday, the third trough takes aim at the
region for later Sunday through Monday. Quite a few of the details
have yet to be worked out by models, but there is general agreement
it will be a potent and cold system, with a healthy moisture tap,
yielding more chances of decent precipitation along with gusty

.AVIATION...For McCarran...VFR conditions along with light winds
favoring typical diurnal trends are expected today. Winds may
increase slightly on Wednesday before the next series of storm
begins to impact the region late Wednesday bringing precipitation
and low CIGs.

For the rest of southern Nevada...northwest Arizona...and southeast
California...VFR conditions are expected across the region through
Tuesday. Light winds favoring typical diurnal trends are expected
today, except along the Colorado River Valley where north winds
gusting 20-25 kts can be expected. Winds will being to favor a
south to southwest direction Wednesday before the next series of
storm begins to impact the region late Wednesday bringing precipitation
and low CIGs.

.SPOTTER INFORMATION STATEMENT...Spotter activation is not expected
today. The next series of storm systems will bring widespread rain
and mountain snow to the region late Wednesday into next week.


Short Term/Aviation...Wolcott
Long Term.............Steele

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