FXUS65 KVEF 180557

Area Forecast Discussion
National Weather Service Las Vegas NV
955 PM PST Thu Jan 17 2019

.SYNOPSIS...Dry weather will return Friday, followed by a warming
trend over the weekend. Another storm system will bring chances for
mountain snow to the Sierra and higher elevations of the southern
Great Basin Sunday night and Monday, along with breezy north winds
and cooler temperatures Monday through Wednesday.

.UPDATE...Recent radar, satellite and surface observations indicate
almost all showers have dissipated within our forecast area and
mainly gusty south to southwest winds 25-30 mph were occurring this
evening...with locally higher gusts near east facing mountain
slopes. A mid level cold pool and associated surface front was
moving from east central Nevada into Utah and there may be a few
showers in eastern Lincoln and far northern Mohave counties
overnight. Snow has ended over the east slopes of the Sierra and
heights were beginning to rise as a ridge builds over the West Coast
behind the upper low moving across Utah into the Rockies. The Winter
Storm Warning for the east slopes of the Southern Sierra has been
cancelled. The PoP/WX/QPF/Snow amount grids have been adjusted
according to these trends. Winds will continue diminishing and will
become northerly over southern Nevada overnight.

227 PM PST Thu Jan 17 2019

.DISCUSSION...Main moisture plume has passed through most of the CWA
and will exit Mohave County this evening. This will bring the risk
of significant precipitation to an end across most of the area. In
the wake of the plume, spotty showers were developing under the mid
level trough axis, mainly affecting Clark and northern San
Bernardino counties as of 2 pm. Farther west, low level moisture was
continuing to flow into the Sierra, bringing more snow to the higher
elevations, so the Winter Storm Warning will remain in place there.
The Sierra were intercepting the moisture very effectively, so
cancelled the Winter Storm Warning for the White Mountains of Inyo
County. Also cancelled the Winter Weather Advisory for the Clark
County mountains, as only snow showers are expected there overnight.
Another issue is wind. The steady rain cleared out quickly today,
taking precipitation drag out of the equation, and allowing strong
winds and trapped lee waves to develop over the western zones.
Surface obs show these winds are just below Wind Advisory criteria
for the most part, so chose not to issue at this time. As we go
through the night, a pool of unstable air with lifted indices of -2
to -3 is forecast to drop southeast through Lincoln County toward
northern Mohave County, so added thunder to the forecast there. This
is supported by a few lightning flashes observed over Eureka and
White Pine counties around 2 pm. By Friday morning, precip chances
should be gone areawide, with clearing skies. Temperatures will warm
up noticeably over the weekend under high pressure before getting
knocked back down as another storm system rolls in Sunday night and
Monday. This storm is not expected to have much moisture to work
with, so precip chances will be small and limited to the Sierra and
the higher terrain of the southern Great Basin. Winds could be a
bigger concern with this storm, with a risk of downslope winds in
the lee of the Sierra on Sunday, and strong northerly winds possible
along with cooler temperatures areawide Monday into Tuesday. The
strong winds could linger in the Colorado River Valley through much
of the week.

.AVIATION...For McCarran...Scattered to broken high clouds
will pass over the terminal through Friday. South to southwest winds
with intermittent gusts to 25kt will continue through most of the
night before winds veer to the northwest as a cold front
approaches/passes the airfield around daybreak Friday. 5-10 knot
northwest winds will gradually transition to northeast by Friday
afternoon. Drainage winds will resume Friday evening.

For the rest of southern Nevada, northwest Arizona and southeast
California...A cold front will continue southward across the area
tonight and turn breezy south to southwest winds to the north, with
lighter winds anticipated with and behind the front. VFR clouds are
expected on Friday with dry conditions. Generally, winds will be
light on Friday except down the Colorado River Valley where north
winds may gust to 25kts in the afternoon.

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



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