Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 192032
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
140 PM PDT Tue Sep 19 2017

.SYNOPSIS...A transition into much more fall-like weather will
occur this week as a cooler airmass from the Gulf of Alaska sweeps
in. Strong and gusty winds are expected in advance of this cool
down, with the strongest winds expected Thursday.  Much cooler
temperatures in store Friday through the weekend with mid and higher
elevations of the southern Great Basin potentially observing their
first freezing temperatures over the weekend.

&&

.SHORT TERM...through Friday.

Fairly tranquil weather conditions across the region aside from some
gusty southwest winds along the I-15 corridor which have persisted
through the day. Anticipate these gusty winds finally subsiding a
bit tonight as pressure gradients relax only be recharged by
Wednesday afternoon as strong early fall trough becomes carved out
over the Pacific Northwest. This will make for a return of the gusty
winds by tomorrow afternoon particularly across the Western Mojave
Desert and along the Sierra.  As the trough deepens Wednesday night
into Thursday it will aim a very strong jet (aided by a potent
thermal gradient) into the region, resulting in widespread strong
and gusty winds. Wind speeds look to peak Thursday afternoon along
the I-15 corridor where widespread gusts of 40-50 mph are looking
possible. A wind advisory for much of the area including Las Vegas
and Barstow will likely be needed in subsequent shifts. Thereafter,
a sharp cold front will cut through region resulting in much cooler
temperatures Friday and much calmer conditions. Friday afternoon
highs on average will be between 12 and 18 degrees below normal,
resulting in a truly fall-like first day of Autumn.

.LONG TERM...Saturday through Monday.

Continuing the theme of fall conditions, attention will turn to the
potential for the first freezes of the season across the southern
Great Basin region, although at this time that potential looks
fairly isolated. A few colder pockets of Lincoln, Nye, and Esmeralda
counties will likely fall into the lower 30s during Saturday and
Sunday mornings.  Even the northern Owens Valley around Bishop will
be quite crisp, with low temperatures in the mid 30s expected over
the weekend.   Elsewhere, seasonably cool mornings can be expected
with dry conditions continuing into next week. The flow pattern for
the weekend and beyond will continue to be dictated by broad
troughing across the Western U.S., promising a continuation of fall-
like conditions into the middle of next week.  &&

.FIRE WEATHER...Expect afternoon breezes through mid week with a
cooling trend and stronger southwest winds by Thursday across the
Mojave Desert region and southern Great Basin. A cold front will
sweep across the area late Thursday bringing light snow chances
above 7000 feet in the southern Great Basin. Critical fire weather
conditions are not expected due to relatively high fuel
moisture and marginal forecast humidities.
&&

.AVIATION...For McCarran...Gusty south to southwest winds will
likely continue through most of the period. Winds may calm down for
a period overnight tonight, but will quickly pick back up tomorrow
morning if they do so. Turbulence and mountain wave hazards will
likely be on the increase by late Wednesday night. With only high
clouds forecast, no operationally significant ceilings are expected.

For the rest of southern Nevada, northwest Arizona and southeast
California...VFR conditions can be expected across the region today
and tonight. A belt of south-southwest winds of 10-20 knots will
persist across southeast California, far southern Nevada and
northwest Arizona through Wednesday.

&&


.SPOTTER INFORMATION STATEMENT...A more fall-like pattern will
bring cooler temperatures and gusty winds over the next week.
While spotter activation is not anticipated, reports of wind
impacts such as blowing dust or damage are appreciated.

&&

$$

Short Term/Long Term.....Outler
Fire.....................Adair
Aviation.................Steele

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