High Wind in California, December 3, 2017

Area Forecast Discussion
National Weather Service Las Vegas NV
853 AM PST Sun Dec 3 2017

.SYNOPSIS...A low pressure system will bring strong winds and
increased high clouds to the region today. The associated cold front
will sweep across the Great Basin and Mojave Desert this afternoon
and evening, bringing gusty north winds and the coldest temperatures
thus far this season. Cool conditions are expected through the work
week with a slight warming trend toward the end of the week. Gusty
north winds will persist in the Colorado River Valley through the
week.
&&

.UPDATE...Update this morning to adjust the forecast winds speeds
and advisory products. Pre-frontal winds have already reached
advisory levels across portions of the Las Vegas Valley and Lake
Mead. As a result I've added Wind Advisories for those areas as
well as Death Valley, all beginning immediately. I've also pushed
back the expiration time of several of the wind products to better
match the latest high-res guidance. While not seen yet in
observational wind data, there has been some blowing dust noted in
the Owen Lake area. Will continue to monitor the situation and
make updates as needed through the day.
-Wolcott-
&&

.PREV DISCUSSION... /issued at 247 AM PST Sun Dec 3 2017/

.SHORT TERM...through Monday night. Main concern is still the storm
system spinning into the Pacific Northwest this morning. Its first
impact for our area will be gusty southwest winds today. Downslope
winds still look like a decent bet on the eastern Sierra slopes and
in the Owens Valley, so left the Wind Advisory in place there. The
strongest gradient pre frontal winds look marginal for an advisory,
but if any zone is going to exceed 40 mph, northern Mohave County
looks like the best bet, so left the Advisory in place there as
well. The next impact will be strong northerly post frontal winds.
The front will sweep south across the southern Great Basin around
midday today and across the Mojave Desert this evening and tonight.
In its wake, widespread gusts of 40 to 45 mph should overspread the
southern Great Basin and far northern Mojave Desert, which is also
already accounted for in the Advisory. Strong northerly winds should
funnel down the Colorado River Valley overnight into Monday morning,
and persist well beyond the short term period, so hoisted a Wind
Advisory there from Monday morning through Tuesday evening. This may
need to be extended later. The last impact will be very chilly
temperatures once the north winds settle down. There is some
question whether the coldest morning will be Tuesday or Wednesday,
depending on when the winds finally diminish. Looks like the
outskirts of the Las Vegas Valley and much of northeast Clark County
will see their first freeze of the season one of the two mornings,
and issued a Freeze Watch for Tuesday morning.

.LONG TERM...Tuesday through Saturday.

Behind the aforementioned cold front arriving late Sunday will be
the coldest temperatures seen this season. The coldest days will be
Tuesday and Wednesday mornings where some low-elevation locations
within the Mojave Desert will drop into the 30s, this includes the
Las Vegas valley. Tuesday morning still looks fairly windy, so
better chances of near freezing temperatures may be on Wednesday
morning where there will be less wind. However, MOS guidance for HND
has been persistent at dropping temps in the low 30s TUE, and other
localized pockets of near freezing temperatures are definitely
possible TUE morning. With model persistence and moderate confidence
for near freezing temperatures TUE morning decided to go with a
Freeze Watch for zones 20 & 16. Fairly gusty north winds are likely
down the Colorado River Valley following the frontal passage with
gusts up to 45-50 MPH. As such, a Wind Advisory was issued from 10am
MON - 8pm WED.

Besides low temperatures and gusty afternoons, high temperatures
should be near seasonal before becoming slightly above normal by the
end of the week as high pressure settles over the region yet again.
With high pressure building back over the region, valleys will
likely see inversions resulting in reduced air quality.
&&

.AVIATION...For McCarran...Southwest winds with gusts up to 25 kts
will begin mid-morning and last through the late afternoon. A cold
front will pass through the valley this evening between 01z-03z,
bringing a brief period of northwest winds 20-25 kts with gusts up
to 35 kts with winds settling down to northerly 10-15 kts around
midnight. Anticipate turbulence downwind of mountains. Skies will
clear this evening.

For the rest of southern Nevada, northwest Arizona and southeast
California...Gusty southwest winds will spread across the area this
morning. Downslope winds and increased turbulence will be possible
along the southern Sierra. A cold front will sweep from northwest to
southeast this afternoon, bringing north winds with speeds 25-35 kts
and gusts up to 45 kts. A prolonged period of gusty north winds can
be expected in the Colorado River Valley for much of the upcoming
week.
&&

.SPOTTER INFORMATION STATEMENT...Strong winds are expected for much
of the area today and in the Colorado River Valley for much of the
week. Spotters are encouraged to report any significant weather or
impacts according to standard operating procedures.
&&

SHORT TERM/AVIATION...Morgan
LONG TERM.............Kryston

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