High Wind in Arizona, April 16, 2018

Area Forecast Discussion
National Weather Service Las Vegas NV
312 PM PDT Mon Apr 16 2018

.SYNOPSIS...A potent spring storm will sweep across the Mojave
Desert today. Wind Advisories and High Wind Warnings are in
effect. Chances for rain and snow today and tonight will remain
north of Las Vegas. The entire southern Great Basin and Mojave Desert will be
much cooler Tuesday. After a quiet and warmer day Wednesday, winds
will increase along with a chance of showers Thursday with next
storm system. &&

.SHORT TERM...through Tuesday night.

Some subtle changes were made to wind speeds from this mornings
update. Wind speeds have been slightly more generous than
previously advertised for the southern Sierra/Owens Valley, Spring
Mountains and across the Nevada Test Site. Hi-res models have
stronger winds speeds in those areas as well, so decided to
increase wind speeds across the southern Sierra/southern half of
the Owens Valley mainly south of Olancha for this afternoon and
across the Spring mountains and the Nevada Test Site.

Some peak wind gusts so far:

*79 MPH at Spring Mt. Youth Camp
*78-55 MPH across the Nevada Test Site
*66 MPH Red Rock Canyon
*61 MPH Kane Springs (Lincoln County)
*56 MPH Near U95 & HWY157
*54 MPH Tweeds Point (AZ Strip)
*53 MPH Five Mile Raws (S Sierra Slopes)
*52 MPH Owens Valley RAWS
*50 MPH Badger Spring Valley (near Alamo, NV)

Decided to upgrade to HIGH WIND WARNING for the Spring Mountains and
western Clark/southern Nye zones. Also decided to issue a WIND
ADVISORY for the eastern Sierra slopes and Owens Valley zones
primarily highlighting the areas south of Olancha where more
enhanced winds will continue through the evening. Primary concern
will be blowing dust and cross winds today and tonight. Motorists
should use extra caution if driving today especially if on US395,
US95, and US93.

Winds will decrease fairly rapidly later this afternoon/evening
before a cold front pushes through the region. Winds behind the
front are not expected to be an issue.

With the frontal band, some slight chances of precip are possible
mainly north of Las Vegas. Hi-res models are indicating that there
could be a slight chance of precip. along the Spring Mountains and
Sheep Range later this evening along the leading edge of the frontal
passage, so bumped up POPs to reflect that. The southern Sierra
Nevada will continue to intercept much of the moisture today with
snow accumulations of 3 to 6 inches possible mainly above
Aspendell, CA. Winter Weather Advisory remains in effect until 3AM
Tuesday morning for the Eastern Sierra Slopes.

Tuesday will be about 10 degrees cooler, drier, and calmer than
today.

.LONG TERM...Wednesday to Monday.

The next system will churn down the west coast and pivot inland
Wednesday then close itself up over Nevada on Thursday. Sensible
weather response will be strong winds and increased precip chances.
Medium-range guidance has remained in good agreement with the
synoptic evolution. The main wind impact from this system will be
north winds on the backside on Thursday. Low-level forecast winds
between 35-45 kts across the southern Great Basin will aid in gusty
conditions across Esmeralda, Nye, and Inyo Counties. Large spread
still exists in north winds speeds between MAV and EC, mainly for
areas north of Interstate 15. Further south, breezy to locally
strong north winds will develop. With a warming cold pool, thermal
gradients aloft should weaken and decrease winds as the move south.
Overall, have taken the conservative approach to winds, with the
forecast favoring ECMWF solution.

In addition to wind, precip chances will increase along the southern
Sierra early early Thurs and spread eastward across the northern
zones Thursday. Precip on the backside of low - as it occludes - has
trended further south compared to previous runs, with 20 percent
PoPs being spread into the Las Vegas valley. Although precip is
expected to be light, will monitor these trends over the next
forecast cycles. There does appear to be slight destabilization
across Lincoln County Thursday afternoon, with CAPE values around
200 J/kg. This may support a few updrafts capable of a few claps of
thunder, but have not included any thunder at this time. Closed low
will progress east on Friday with precip chances tapering from west
to east as well. Northerly breezes will likely linger through Friday
across the region. By the weekend, ridging nudges inland bringing a
period of fair weather to area.

Temperatures will be around normal Wednesday, decrease Thursday
under height falls, then increase 3-6 degrees each day through
Sunday under the influence of an upper ridge.
&&

.AVIATION...For McCarran...Strong southwest winds will continue
this afternoon and peak early this evening with frequent gusts
around 40 knots expected. Wind speeds will gradually decrease toward
midnight and become northwest after midnight through early Tuesday
morning as a cold front passes. FEW-SCT clouds with bases 080-100
kft can also be expected. A northeast to east component generally
less than 8 knots should develop Tuesday afternoon and evening.

For the rest of southern Nevada, northwest Arizona and southeast
California...Widespread southwest winds gusting 35-50 KTS expected
through this evening. Mechanical turbulence below 18 kft downwind of
mountains can be expected this evening. A cold front will push south
across the region tonight/early Tuesday morning with northwest-north
winds of 10-20 knots and scattered snow showers across south central
Nevada. Winds will decrease below 10 knots for most areas except the
lower Colorado River Valley by Tuesday afternoon.
&&

.FIRE WEATHER...Strong winds, low relative humidities and dry
fuels across the southern half of Mohave County and the Lower
Colorado River Valley will create critical fire weather conditions
through tonight. As such, a Red Flag Warning remains in effect
today through this evening for northwest Arizona and the lower
Colorado River Valley.
&&

.SPOTTER INFORMATION STATEMENT...Widespread strong winds are
expected to continue this afternoon through the evening. Spotters
are encouraged to report any wind damage and/or visibility
restrictions due to blowing dust. &&

SHORT TERM/FIRE WEATHER...Kryston
LONG TERM...Boothe
AVIATION...Adair

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