High Wind in California, February 3, 2021

Area Forecast Discussion
National Weather Service Las Vegas NV
644 AM PST Wed Feb 3 2021

.SYNOPSIS...A weather system will move into the region today and
bring increasing winds to most of the area through Thursday.
Temperatures will be a few degrees above normal Wednesday and drop
to a few degrees below normal on Thursday and Friday before
climbing through the weekend. &&

.UPDATE...Quick update to today's min and max temperatures for
Las Vegas and Desert Rock to indicate better hourly trends and
bump up the high's this afternoon considering very warm morning
temperatures and continued mixing plus mostly sunny skies should
warrant slightly warmer temperatures. &&

.PREV DISCUSSION... /issued at 317 AM PST Wed Feb 3 2021/

.SHORT TERM...Today through Friday.

A low pressure system currently spinning across Oregon will continue
to dig into the Great Basin through the day today which will create
increased pressure gradients across our region, resulting in a belt
of gusty west-southwest winds. So far, enhanced winds of 40-55 mph
have been observed across the Spring Mountains due do a strong upper-
level jet stream moving overhead. These winds have even translated
down to portions of Highway 95 northwest of Las Vegas to Desert
Rock where south- southwest gusts of 30-40 mph are being observed
this morning. Only the highest model guidance correctly indicated
these winds this morning, which were used to populate this
mornings forecast winds. Based on these observations and trends,
the current Wind Advisory looks in good shape. Took a look at the
potential for downslope winds in the Sierra reaching the Owens
Valley floor, but based on both the 7.5km and 2.5km local model
cross-sections, winds won't quite make it to the valley floor.
Downslope winds around 50 mph still look possible especially across
Red Rock Canyon and gusts to 40 mph across parts of southwest Las
Vegas Valley early Wednesday morning. However, winds across northern
and eastern portions of the Valley might only see gusts to 20-30
mph. The strongest belt of winds are still expected to be across
northern San Bernardino, southern Clark, and north- central Mohave
counties through this afternoon where Wind Advisories will be today
through 7pm. Wind speeds across lakes Mead and Mohave aren't
expected to be as strong, with gusts to about 35 mph creating wave
heights to 2 feet, where a Lake Wind Advisory will be in effect
until 7pm.

Southwest winds will quickly decrease by this evening as a surface
cold front begins to move through southern NV. The front itself
isn't expected to be particularly strong, only decreasing
temperatures Thursday afternoon by 6-8 degrees from today's
temperatures. In addition to cooler air with the front moving
through tonight into Thursday morning, expect breezy to gusty
northerly winds. Per usual with northerly winds, the strongest
winds are expected down the Colorado River Valley Thursday, where
gusts to 25-35 mph will be possible mainly from Laughlin to Lake
Havasu.

Since winds have remained elevated overnight across parts of the
Vegas Valley, temperatures have remained fairly warm overnight. As
of 3 am, KLAS is sitting at 60 degrees which is 14 degrees warmer
than this time 24 hours ago. The current record high minimum is 50
degrees for Las Vegas today, and based on current conditions and
trends, has a decent chance of being broken today.

Besides winds and temperatures, the previously slight chances of
precipitation have since diminished with almost negligible
chances expected now across isolated areas of northeastern Lincoln
and Mohave counties.

By Friday, the area will be under dry northwesterly flow, resulting
in clear skies and lingering breezy north winds.

.LONG TERM...Saturday through Tuesday.

A dry northwest flow will set up over the Desert Southwest by the
end of the week. Afternoon breezes will be possible as this set up
is typically favorable for shortwaves to ride along the flow.
Otherwise, heights will rise, resulting in temperatures climbing to
above-average through the weekend and the start of the work week.

Models indicated yesterday the potential for the cut-off low that
split from our wind-making trough to to move inland late Sunday
night into Monday, but this has since changed, and thus, little to
no impacts are anticipated from this low as a Pacific ridge builds.

Sunny skies and above-average temperatures expected to provide a
very pleasant February weekend. Confidence is low regarding the
extended forecast past Monday.
&&

.AVIATION...For McCarran...Moderate wind impacts expected today for
the McCarran terminal. As of TAF issuance, winds were beginning to
increase out of the south, varying between 150-200 degrees. This
will likely continue through the first couple hours of the TAF
period before eventually shifting to southwest to prevail the rest
of the day. When the wind shift occurs, an increase in gust
potential up to 30 kts will be possible, likely after 16Z. Prior to
16Z, increasing winds aloft may result in low level turbulence and
borderline LLWS. Did not add this to the TAF though as confidence
was not high. Will monitor PIREPs if a short fuse amendment is
needed. Winds will continue to be gusty out of the southwest through
this evening, then an abrupt change to a northwest direction will
occur as a cold front moves through the Valley. Timing is moderate
confidence but and winds are expected to be initially gust while
gradually subsiding through early morning hours tomorrow morning.

For the rest of southern Nevada, northwest Arizona and southeast
California...Windy conditions are expected today for many regional
terminals and additionally, region wide low level turbulence will be
possible due to high winds aloft (>45 kts above 2kft). Most
significant impact may be KBIH today as LLWS concerns will continue
through the first 5-6 hours of the TAF period. Still unclear whether
strong west-southwest winds will be able to reach the terminal but
winds just aloft should be strong, hence the LLWS mention in the
TAF. Elsewhere west-southwest winds are expected to bring minor to
moderate wind impacts to each terminal. However, clouds are expected
to stay aoa 12kft.

Update/Short Term...Kryston
Long Term...Varian
Aviation...TB3

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