Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 210907

Area Forecast Discussion
National Weather Service Las Vegas NV
207 AM PDT Wed Oct 21 2020

.SYNOPSIS...Warm and dry conditions will continue today before a
gradual cooldown tomorrow through Saturday. A pattern change will
bring much cooler and blustery conditions Sunday into early next
week, with chances for rain and mountain snow showers Sunday and

.SHORT TERM...through Friday. Early morning satellite loop showed
the Rex block still in place at 140-150W and a small circulation
passing through southern California with little fanfare. Well to the
north, a shortwave trough was seen digging southward through British
Columbia. More on this feature, which will be the first ingredient
in our upcoming pattern change, in a moment. First, note that KLAS
topped out at 89 degrees yesterday, so the number of 90 degree days
in the year still stands at a record-tying 158. The forecast for
today is exactly 90 again, so it will be a close call whether the
record will be broken today or not. The shortwave trough over BC
this morning will dig through the northern Rockies tonight, dropping
our temperatures a few degrees tomorrow. Given the upcoming pattern
change, today is almost certainly KLAS` last shot at 90 degrees this
calendar year. Temperatures will come down another five degrees or
so areawide on Friday as high clouds begin to move in from the
south. Aside from southwesterly breezes in the afternoons, little
other sensible weather expected through Friday.

.LONG TERM...Saturday through Wednesday.

Ensembles continue the trend for a deeper/colder trough early next
week with a slower recovery through mid-week as a closed low could
linger over Arizona into Wednesday.

Ahead of the deepening trough Saturday a belt of stronger southwest
winds looks to develop across the western Mojave Desert. Pockets of
those stronger winds may develop in Clark and Mohave Counties as
well. Any consideration for fire weather headlines looks low at this
time based on current forecast winds and RH values. Will continue
monitor need in the coming days.

Final piece of energy digging down front-side of amplified eastern
Pacific ridge is forecast to form a closed low over the region. GEFS
continues to place the closed low further east over western Arizona
while the ECMWF Ens. and Canadian Ens. are a tad further west over
southern Nevada and southern California. Forecast temperatures
continue to trend downward, in fact Monday`s high will be about 30
degree colder than today`s high. Note: If those values hold we will
be threatening some of our low maximum records for October 26.
Likely need our first freeze headlines for all but the lower deserts
Monday and Tuesday mornings as well.

Will the Las Vegas record stretch of no measurable rainfall be
coming to and end? Precipitation chances looking better Sunday and
Monday, possibly lingering into Tuesday for Mohave County as the
closed low meanders in our vicinity.

.AVIATION...For McCarran...Light winds will continue today
and tonight with easterly components in the late morning and
afternoon and southwest components overnight. Skies will remain
mostly clear aside from areas of smoke aloft from fires in the
Sierra Nevada.

For the rest of southern Nevada, northwest Arizona and southeast
California...Winds will remain generally less than 10 knots today
and tonight at TAF sites around the region. Wildfire smoke will
continue to impact the Owens Valley with low visibility and areas of
mountain obscuration. Areas of smoke aloft will drift around the
region but no significant clouds.

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


LONG TERM...Pierce

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