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Area forecast discussion
National Weather Service Las Vegas Nevada
916 PM PDT sun Sep 15 2019

Synopsis...a low pressure system dropping down from the
Pacific northwest will move across the southern Sierra and Great
Basin on Monday bringing windy conditions and significantly cooler
temperatures by Tuesday. Another weather system will follow a
similar track and bring more wind to the region Wednesday through

Update...multiple sensors along the eastern Sierra slopes are
reporting southwest to west wind gusts generally ranging from
25-30 mph this evening. This is in response to increasing winds
aloft as a sharp trough approaches the northern California
coast. Conditions will remain favorable through the overnight
hours for downslope winds occasionally reaching the lower slopes
along the western edges of the Owens Valley. A few light showers
and even an isolated thunderstorm was seen over Mohave County
earlier this afternoon/evening. This activity has moved away from
the area and precipitation is no longer expected overnight.
Locally gusty winds will continue through the night with the
strongest winds expected across the Sierra crest. Expect partly to
mostly cloudy conditions tonight.

Previous discussion... /issued at 215 PM PDT sun Sep 15 2019/

Discussion...through next Sunday.

Increasing winds will be the main weather concern through Monday
evening as a Pacific northwest trough slowly digs down the coast
tonight then swings inland across northern California and northern
Nevada Monday. There will also be limited moisture and instability
over eastern Mohave County for a slight chance of
afternoon thunderstorms through Monday.

Conditions will still be favorable in the southern Sierra and Owens
Valley for periods of strong downslope winds though the latest high
resolution models have trended downward slightly with wind speeds.
Gusts of 35 to 45 mph appear likely this evening and overnight,
primarily in the foothills west of Highway 395, then winds should be
confined to the mid and upper slopes Monday morning through early
afternoon. This will be followed by favorable strong downslope
conditions as the trough axis and cold front move over the region
late afternoon through the evening where gusts will likely push
across areas of Highway 395...especially between 5 PM and 9 PM. It
appears gusts of 40 to 50 mph will be likely and a Wind Advisory was
issued to replace the high wind watch from 2 PM Monday afternoon
until 9 PM Monday evening.

Elsewhere across the region, the belt of strongest southwest winds
will set up across southern/central Nye and Lincoln counties late
Monday morning through early Monday evening and a Wind Advisory has
been issued from 2 PM Monday afternoon until 9 PM Monday evening for
zones north of the Las Vegas Valley. Gusts in the Spring Mountains
and Sheep Range on exposed ridges above 7000 feet of 40 to 50 mph
can be expected, but Red Rock Canyon, the Las Vegas Valley and areas
to the south will likely see gusts generally in the 30-35 mph range
Monday and impacts should be minimal.

Winds will diminish Monday night and remain fairly light Tuesday
behind the system lifting away to the northeast. Another trough is
then forecast to drop down from the Pacific northwest into central
and southern Nevada late Wednesday through Thursday before lifting
away Friday leaving a weak zonal pattern in place going into next
week with yet another upstream trough possibly brushing our region
late Sunday. This pattern will keep breezy periods with temperatures
near or slightly below normal.

Aviation...for McCarran...after a brief lull in winds tonight,
southwest winds will begin increasing shortly after daybreak on
Monday, and continue increasing through the afternoon with a few
gusts to 30 kts possible. The thickest clouds will arrive tonight
and begin to thin tomorrow, but ceilings are expected to remain
above 15 kft. Along with the gusty winds, a few elevated showers may
try to develop, enhancing turbulence potential, though any rain is
not likely to impact the terminal. Winds will quickly decrease, but
remain southwest after sunset Monday evening.

For the rest of southern Nevada, northwest Arizona and southeast
California...southwest winds will increase for all terminals for
Monday. Strong surface winds will Foster turbulence and low-level
wind shear hazards across much of the area as well as mountain wave
action in the Owens Valley. A few thunderstorms may develop in
northwest Arizona, with elevated showers elsewhere, but
precipitation is not anticipated to reach the ground, and ceilings
should remain at or above 15 kft. Winds will begin to quickly
subside after sunset Monday evening.

Fire weather...a strong low pressure system will bring gusty winds
to Inyo County tonight then spreading across most of southern Nevada
Monday. A red flag warning is in effect for Inyo County California
zones from until 9 PM PDT Monday. A red flag warning is in effect
for the southern Nevada zones from 11 am Monday morning until 9 PM
PDT Monday evening. A belt of strong southwest winds gusting 35 to
45 mph is forecast for the southern Great Basin. These strong winds
will be accompanied by minimum relative humidity values in the single-digits to
lower-teens. Winds will decrease Monday night through Tuesday then
another trough will increase winds across the region late Wednesday
through Friday.

Spotter information statement...spotters are encouraged to report
any significant weather or impacts according to Standard operating



Discussion/fire weather...Adair

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