Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 212127

Area Forecast Discussion
National Weather Service Las Vegas NV
227 PM PDT Mon May 21 2018

.SYNOPSIS...A low pressure system will produce scattered showers and
isolated thunderstorms through Tuesday mainly for areas north of
Interstate 40. Dry and mild conditions can be expected during the
middle of the week then unsettled weather is on the horizon for the
holiday weekend as another Pacific System appears to be taking aim
on our region.

.SHORT TERM...through Thursday night.

Showers and isolated thunderstorms should become a little more
enhanced as the afternoon progresses in an arc from Clark/Mohave
counties up across central Nevada and northern Inyo County. This is
the northeast quadrant of the upper low which was centered over the
area between Barstow and Death Valley this afternoon. Any rainfall
impacts should be limited by the speed of the cells, NNW at 20-25
mph, and the modest increase in moisture in the boundary layer with
surface dewpoints in the 40s will limit downburst potential. Showers
will diminish somewhat this evening but the upward forcing
associated with the closed low will keep a few showers going around
overnight. The low center is forecast to lift across southern Nevada
Tuesday morning then continue northward Tuesday night and Wednesday.
Showers and isolated thunderstorms will be confined mainly from the
Spring Mountains and areas to the north on Tuesday then some
lingering convection mainly over the southern Sierra Wednesday and
Thursday. Southerly flow will increase Thursday afternoon ahead of
the Eastern Pacific System that now looks like will have a bigger
effect on our region after Thursday. Temperatures will climb a few
degrees each to put highs back above normal Wednesday and Thursday.

.LONG TERM...Friday through Memorial Day.

It appears that the weather pattern is taking a turn for the worse
going into the holiday weekend and conditions are now looking less
pleasant for outdoor activities...primarily due to gusty southwest
winds Friday and Saturday and the potential for least
in the mountains. The rather abrupt change in the weather pattern
from the medium range models keeps confidence in the details is so
low that the mountains are the only place where a mention of showers
has been added to the forecast, but they could be more extensive if
the 12Z GFS solution ends up closer to reality. The medium range
models are now coming into good agreement at depicting yet another
large closed Pacific Low moving across California into southern
Nevada and northwest Arizona Saturday and Sunday. As usual, there
are differences in the track of the low center, but it is depicted
to be pretty close to or over southern Nevada by Saturday afternoon
then it lifts up across Utah Saturday night and Sunday and remains
somewhat stationary on Memorial Day. Temps, winds and PoP/WX grids
were adjusted using a blended approach which incorporates both the
GFS and ECMWF solutions. Those with outdoor plans should stay tuned
for further updates as details become a little more clear the next
few days.


.AVIATION...For McCarran...Scattered showers and thunderstorms will
remain possible through the evening hours. These storms and their
associated outflow boundaries will make the wind forecast tricky.
anticipate east or southeast winds this afternoon and evening will
continue unless otherwise disturbed by storm activity. CIGS in the 8-
12kft range are expected, with decreasing clouds and showers
expected late this evening. Fair weather cumulus expected tomorrow
with shower chances limited to the higher terrain west and south of
the airfield.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered showers and thunderstorms will remain
possible through the evening, with the best chances over Inyo,
Esmeralda, Nye and Clark County.  Gusty winds can be expected near
shower activity, with CIGS generally between 8-12kft AGL. Pockets of
convective turbulence can be expected. Improving conditions are
expected overnight with a few terrain driven showers possible again

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



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