High Wind in Nevada, October 18, 2021

Area Forecast Discussion
National Weather Service Las Vegas NV
923 PM PDT Sun Oct 17 2021

.SYNOPSIS...Winds will increase this evening, peak overnight, and
decrease on Monday as a cold front moves through the area, leaving
cooler temperatures in its wake Monday and Tuesday. Less wind and
gradually warming temperatures are expected through the latter part
of the week.
&&

.UPDATE...Southwesterly winds have started to ramp up across the
Sierra Mountain crest, with observations generally between 30 and 40
mph as of 9pm. The highest recorded gust so far this evening was in
far northern Owens Valley at Pine Creek with a gust of 64 mph. These
wind speeds will continue to increase through the overnight hours,
which may lend themselves to a forecast update as they materialize.
For now, the winds are on par with the forecast, so no updates have
been made. Winds will increase along a belt from western San
Bernardino County up through southern Nevada to northern Mohave
County around sunrise, remaining elevated through the morning and
peaking just after your morning commute. Winds will be particularly
dangerous along Highway 95 near Mercury-Desert Rock, where winds
will be strong and perpendicular to the roadway. High-profile
vehicles are discouraged from taking Highway 95 through mid-morning
for this reason. Additional Wind Advisories will be considered
overnight as this wind event comes to fruition - especially if winds
start to overacheive local high-res model data. For the near term,
the forecast lines up well with ground truth.
&&

.PREVIOUS DISCUSSION...210 PM PDT Sun Oct 17 2021/

.SHORT TERM...through Monday night. Midday satellite loop showed
high clouds streaming over our area ahead of the long-advertised
upper level trough which was nearing the coast of far northern
California. Surface winds were beginning to respond, with exposed
stations seeing southerly winds gusting into the 20s and 30s. The
stronger winds and better mixing had also kicked temperatures up a
few degrees from yesterday, although this was not yet being felt in
many valleys (such as the Owens, Las Vegas, and Colorado River
valleys) where the winds had not yet made it down to the valley
floors. The main focus for this evening through tomorrow morning is
still wind. Wave clouds were becoming more pronounced in the lee of
the central Sierra, and these will spread south through the day with
the belt of stronger cross-barrier winds. Wind Advisory for the
Owens Valley and eastern slopes of the Sierra beginning late this
afternoon still looks good. High resolution models are suggesting
that the strongest downslope winds will not penetrate as far east as
Highway 395, but even if this verifies, rotor circulations will
result in sudden wind shifts and gusts along the highway. Winds will
likely peak in this area in the wee hours of the morning, by which
time south to southwest winds in the Spring Mountains will also be
kicking up. The Wind Advisory for the mountains themselves looks
good, with lingering questions about any downsloping. High res
models are still pinpointing southerly downslope coming off the
northwest end of the mountain range, with a short period of gusts
over 40 mph reaching Highway 95 near Mercury-Desert Rock between
about 3 and 7 AM. If this verifies, it would affect such a small
percentage of the forecast zone that it would be best handled
through social media and direct partner interaction rather than
through expanding the Advisory. Other areas of concern include the
Barstow and Kingman areas. For the Barstow area, the high res models
have been consistent in showing the strongest winds remaining north
of I-15 and the populated areas, so chose not to expand the Advisory
into this zone. The Kingman area is a bit tougher, as the models
show peak winds Monday hovering just under 40 mph for large swaths
of the zone, including Kingman proper. Run to run trends are nearly
flat, so that doesn't help much. For now, will forgo an Advisory for
that area and message it via social media and direct outreach. High
temperatures Monday will come down 10 to 15 degrees from today in
the wake of the cold front, with little to no impact expected from
post-frontal northerly winds. Precipitation chances will be confined
to the Sierra and southern Great Basin, with a couple of inches of
snow on the higher elevations of the Sierra and very light rain and
snow from northern Esmeralda County to northern Lincoln County.

.LONG TERM...Tuesday through Saturday.

The system that will bring with it a gusty Monday morning will also
drop temperatures substantially, with Tuesday's afternoon highs
dropping to 8-12 degrees below seasonal averages. That said, in the
system's wake, a ridge of high pressure will set up across the
Desert Southwest that will bring dry weather and will allow
temperatures to slowly climb back to normal through the week and
into the weekend.

There continues to be an indication of a strong weather system
impacting our area at the end of the work week and through the
weekend. Though there remains quite a bit of uncertainty regarding
strength, timing, and position, the NBM seems sold on impacts on the
northern portions of our CWA, with at least "slight" PoPs across the
higher elevations of Inyo County and across the southern Great Basin
for the weekend as well as a drop in temperatures. Will continue to
monitor trends through the week.
&&

.AVIATION...For McCarran...Easterly winds up to 8 knots are
expected to transition to the south and southwest this afternoon.
Wind speeds are expected to increase and become gusty as the winds
transition. There could very well be a period of time of a southeast
component to the winds prior to turning predominantly south to
southwest. Winds remain gusty overnight from the southwest then
increase Monday morning with wind speeds around 20 knots and gusts
around 30 knots. The gusty winds will gradually subside Monday
afternoon and turn more to the west or northwest. High clouds will
move across the area at times but no operational impacts are
expected.

For the rest of southern Nevada, northwest Arizona, and southeast
California...Gusty west to southwest winds will continue at most
sites with the exception of the lower Colorado River sites where
more southerly winds are expected this afternoon. The wind forecast
for KBIH is a difficult one and remains of low confidence.
Initially, southeast winds around 15 kts and gusty are expected but
then the forecast calls for winds to turn to the southwest before
turning back to the southeast overnight. Shower chances increase at
KBIH between 09z-12z when cigs could fall to 5k feet or lower.
Shortly after the shower activity ends, winds should turn northerly.
Expect strong turbulence through tonight in the lee of the Sierra.
High clouds will move across the area at times but no operational
impacts are expected.
&&

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

UPDATE...Varian
SHORT TERM...Morgan
LONG TERM...Varian
AVIATION...Salmen

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