High Wind in Arizona, February 13, 2021

Area Forecast Discussion
National Weather Service Las Vegas NV
830 AM PST Sat Feb 13 2021

.SYNOPSIS...A fast moving weather system will bring widespread
strong winds to the Mojave Desert and southern Great Basin region
today along with areas of blowing dust. A few light showers are
possible as well mainly across the Sierra, southern Nevada and
northwest Arizona. Additional disturbances will bring another shot
of wind on Tuesday along with periods of mid and high clouds.

&&

.UPDATE...Surface winds are already on the increase this morning
across the Sierra and western deserts as broad 500mb trough pushes
into the Great Basin and a 125+ knot upper level jet takes aim at
the region.  Went ahead and nudged the start time of our high wind
products forward to begin now in the Sierra, Owens Valley, and
Western Mojave Desert, though strongest winds are still antipcated
during the early afternoon hours out there.

Elsewhere, wind products remain in good shape though I did add Lake
Mead and Mohave regions to the wind advisory for this afternoon and
evening with some convectively enhanced winds looking more likely as
the front moves through. A stray lightning strike is possible mainly
across southern Nevada and Northwest Arizona as a -25C cold pool at
500mb moves through at peak heating, resulting in 100-400 j/kg of
CAPE, mainly from Las Vegas north and east.  Forecast updates have
been sent out and will be taking a closer look at any products
needed tomorrow and fine tuning of the current products with the
afternoon pacakge.

-Outler-

&&

.SHORT TERM...through tonight.

Satellite imagery shows clouds spreading over the region ahead of
a trough of low pressure that will drop in over the area today.
Although the system is expected to bring some light precipitation
to the Sierra and to parts of southern Nevada and northwest
Arizona today, the big concern is impacts related to strong winds.
High Wind Warnings and Wind Advisories are in effect for this
afternoon and evening across much of the region. The highest
impacts are expected along the Sierra Eastern slopes into the
Owens Valley and in the western portions of San Bernardino County
as strong westerly pre-frontal winds increase this morning and
intensify this afternoon. Wind gusts exceeding 60 mph are likely
in these areas for multiple hours which will create difficult
driving conditions on Highway 395 along the Owens Valley to the
western portions of San Bernardino County. This is especially true
for high profile vehicles along 395 in the Owens Valley which
could encounter strong westerly crosswinds. Travelers along main
arteries like Interstates 15 and 40 and secondary highways in San
Bernardino County will encounter strong winds today which may be
accompanied by areas of blowing dust and reduced visibilities,
possibly to near zero at times. Avoid traveling in these areas
today if possible otherwise exercise extreme caution when
encountering these winds. Across our northern zones, a cold front
will bring strong post frontal northwest winds this afternoon with
gusts of 40-50 mph possible. Wind gusts up to 50 mph could reach
the northwest part of the Las Vegas Valley late this afternoon
with the central and southern parts of the valley seeing gusts in
the 30-40 mph range. Expect the gusty winds to continue tonight.

.LONG TERM...Sunday through mid-week next week.

The synoptic pattern after today's shortwave passage will begin to
undergo more of a longer term change from the looks of mid to long
range ensemble projections. Not much change in the expectations for
Sunday through Tuesday, as northwest flow prevails in the wake of
today's wind event. We will have one last opportunity for precip for
the northern and eastern portion of the CWA Tuesday as the last of
our nearly regular pattern of lows will push to the northeast of the
region. However, this system is looking less and less like a precip
producer and more of northerly wind producer, just less significant
as compared to today.

All eyes then shift to the Pacific, where a stout high pressure
system will be the main player in how the rest of the week and
possibly the weekend will be shaping up. Impressively, nearly two
thirds of the inter-ensemble member variance is explained by the
positioning of the ridge axis from this high, whether that will be a
more off shore orientation or east tilt into the northwest US.
Neither outcome bodes well for precip chances and are generally
unfavorable for systems to originate from the Pacific. As a result,
the progressive, cooler/wetter pattern as of late will begin to
shift more towards warmer and drier, especially if the ridge indeed
shifts farther east. The long term ensemble consensus is more or
less indicating a flatter, more zonal flow regime by the weekend due
to a weakening Pacific high but beyond day 7, the signal favors the
high staying intact, if not restrengthening into the following week.
For temperatures, this may mean more seasonable normals or slightly
above normals...for precip, this would be pretty bleak. Either way,
a period of generally low impact looks to be on the horizon as it
stands beyond Tuesday.

&&

.AVIATION...For McCarran...A fast moving low pressure system
dropping down from northern California will quickly move across
southern Nevada today bringing gusty northwest winds 30-35 knots to
the terminal area late this afternoon and evening. Brief rain
showers will also be possible from 21Z to 00Z with clouds bases
generally 080-100 kft AGL. Northwest winds gusting 25-30 knots will
likely persist tonight through Sunday morning behind the departing
system.

For the rest of southern Nevada, northwest Arizona and southeast
California...A fast moving low pressure system dropping down from
northern California will quickly move across the region today
producing areas of moderate to severe turbulence. This system will
bring exceptionally strong west to northwest winds gusting over 50
knots to much of southeast California including the Owens Valley and
western Mojave Desert between 18Z this morning and 03Z this evening.
Strong Northwest will push down through southern Nevada and
northwest Arizona this afternoon and evening with widespread gusts
30-40 knots. Scattered showers can also be expected this afternoon
and early evening with clouds bases generally 100-120 kft MSL.
Northwest winds gusting 25-35 knots will persist across the region
tonight through Sunday morning.
&&

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

SHORT TERM...Salmen
LONG TERM...TB3
AVIATION...Adair

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