Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 180957
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
257 AM PDT Wed Oct 18 2017

.SYNOPSIS...A weak disturbance will bring a slight chance of light
showers to the higher elevations in southeast California this
morning, and southern Nevada and northwest Arizona this afternoon
and evening. Otherwise, dry weather is expected through Thursday
with temperatures a few degrees above normal. A storm system will
bring a risk of downslope winds on the east slopes of the Sierra
Thursday night and strong west winds across the Mojave Desert on
Friday, along with cooler temperatures for Friday and Saturday.
Quiet weather is expected to return for Sunday and much of next
week.
&&

.SHORT TERM...through Saturday. Thicker clouds were expanding over
southeast California and beginning to push into far western Nevada
as of 230 AM, associated with the weak shortwave trough approaching.
The moisture is confined to the mid and upper levels, with the lower
levels remaining dry, thus little or no measurable rain is expected.
Virga and a few sprinkles are more likely, with the possibility of
strong winds near any sprinkles or virga shafts due to the dry low
level air in place. Models still show little or no instability, so
left thunder out of the grids, but would not be surprised to see a
very few lightning strikes. Once this disturbance exits to the east
by early Thursday morning, quiet weather will return for a day
before the next, stronger storm system reaches the West Coast
Thursday night. This system will bring a risk of downslope winds on
the eastern slopes of the Sierra Nevada Thursday night and Friday
morning, along with increasing west to southwest winds over the
Mojave Desert for much of the day Friday. As the associated cold
front sweeps south, winds will shift to northerly across the
southern Great Basin Friday, then over the Mojave Desert Friday
afternoon and evening. It appears that any precip chances with this
storm will be limited to the Sierra and the higher elevations of the
White Mountains. Behind the cold front, strong north winds down the
Colorado River Valley may require a Wind Advisory on Saturday.
Temperatures will be around five degrees above normal Wednesday and
Thursday, then fall below normal by Saturday in the wake of the
front.

.LONG TERM...Saturday night through Wednesday.

Model consistency late this weekend into early next week is poor in
handling the exit of the previous storm system to the east and the
entrance of high pressure over the Southwest. Confidence in the
strength and positioning of these two features is low but in general
a dry pattern will result for the Desert Southwest with either
scenario. Temperatures should rebound quickly back to normal on
Sunday and creep above normal Monday and Tuesday under sunny skies.
North to northeast winds may remain breezy each day; especially down
the Colorado River Valley where gusty conditions are expected to
continue.
&&

.AVIATION...For McCarran...Clouds will increase today in the
12-15K ft layer, with virga and a few sprinkles possible. Away from
virga, light winds favoring typical diurnal trends are expected, but
erratic and gusty winds will be possible near virga. Quiet weather
is expected for much of Thursday, then southwest winds will increase
Thursday night and Friday ahead of a cold front, which will bring a
shift to northerly winds Friday evening.

For the rest of southern Nevada, northwest Arizona and southeast
California...A weak disturbance passing through will bring ceilings
around 15K ft MSL today and tonight, with a few high based
showers/virga. Erratic gusty winds will be possible near any showers
and virga, with light winds expected elsewhere. Quiet weather is
expected Thursday, then a stronger storm system will bring
increasing west to southwest winds across the Mojave Desert Friday,
along with a risk of downslope winds on the eastern slopes of the
Sierra Nevada. Increasing north winds will spread from the southern
Great Basin Friday morning to the Mojave Desert Friday afternoon and
evening behind a cold front.
&&

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

$$

Short Term/Aviation...Morgan
Long Term...Guillet

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