Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 230415

Area Forecast Discussion
National Weather Service Las Vegas NV
914 PM PDT Wed Mar 22 2017

.SYNOPSIS...A Pacific system will bring a chance of showers and
thunderstorms to portions of the area tonight, and into Thursday
over Lincoln, Clark and Mohave counties. Otherwise, expect breezy
winds and seasonal temperatures through Thursday. A second system
will move into the area late Friday into Saturday bringing another
round of showers to portions of the area.

.UPDATE...Area of showers and thunderstorms that developed mid-
afternoon in far eastern Clark, eastern San Bernardino and Mohave
Counties has progressed east into central Arizona this evening.
Radar still detecting isolated showers along with a stray
thunderstorm over Mohave, southeast San Bernardino, Esmeralda, Nye
and Inyo Counties. Upper trough responsible for the showers will
slowly move east through Thursday morning then move into the Four
Corners late Thursday afternoon. 00z NAM/GFS and HRRR still showing
a broken line of showers sliding southeast through southern Nevada
tonight. Then primarily Lincoln and Clark County Thursday morning.
Broken line is coincident with cold frontal passage which still
looks to be around 9 am tomorrow morning for Las Vegas. Lingering
instability could be just enough to set off a chance of showers
along with a slight chance of thunderstorms in Mohave County
tomorrow afternoon. Updated POPs for the rest of tonight and

Transitory shortwave ridge will bring an end to the precipitation
chance Thursday night-Friday morning Leading edge of precipitation
associated with next trough looks to reach western Inyo County
Friday afternoon.

.AVIATION...For McCarran...Southwest winds overnight generally 10-
15kts with gusts up to 20 kts at times. The winds are expected to
turn to the northwest with the best timing between 14Z and 16Z
Thursday morning. Winds should then stay primarily out of the
northwest through the day. There remains a small chance of rain
showers along the cold front Thursday morning. Dry conditions are
expected in the afternoon.

For the rest of southern Nevada, northwest Arizona and southeast
California...Light showers and a few thunderstorms are possible
through the night into Thursday morning. A few storms may redevelop
Thursday afternoon over far eastern Lincoln and Mohave counties.
Southwest winds gusting 20-30 knots will persist ahead of front
moving south and east through the area tonight. Winds will turn to
the northwest behind the front and be locally breezy.

.PREV DISCUSSION...308 PM PDT Wed Mar 22 2017
.SHORT TERM...through Saturday night.

A low pressure system will move across the southern Great Basin and
Mojave Desert tonight and then into Utah and Arizona Thursday. This
will bring plenty of cloud cover and an increasing chance of showers
tonight which will linger across portions of the area on Thursday.
The latest HRRR has been nudging a line of showers it had forecast
earlier over the Spring Mountains further east and now has the line
mostly east of Las Vegas...focused primarily on the Lake Mead NRA,
southeastern Lincoln and northern Mohave counties. There is also a
second area of shower activity forecast along the front as it moves
south and east through the southern Great Basin tonight into early
Thursday. Counties potentially impacted include portions of Inyo,
Esmeralda, Nye, Lincoln, Clark and Mohave. The HRRR forecast lines
up fairly nicely with the 18z NAM12 in where showers are expected to
develop and move. Thunderstorms will be possible through this
evening but should tail off behind the front. Eastern Lincoln and
Mohave counties will be the focus areas for showers and
thunderstorms Thursday afternoon as moisture wraps around the back
side of the low. Gusty winds...southwest to west ahead of the front
and northwest behind...will affect the area through Thursday as

Shortwave ridging and area wide dry conditions are expected Thursday
night and Friday as a ridge axis shifts across the region. A second
trough will bring another round of showers beginning in the Sierra
Friday evening and spreading south and east through Saturday. In
addition, local breezy conditions will be possible. Showers end
overnight Saturday as the system moves east of the area.

Expect seasonal temperatures through Saturday.

.LONG TERM...Sunday through Tuesday. Model agreement is pretty good
through Sunday, but quickly deteriorates thereafter, so confidence
beyond Sunday is low. Solid model to model and run to run
consistency on ridging for Friday points to a dry day with
temperatures rising back to a few degrees above normal. Next storm
passing through Saturday looks like a quick hitter, with precip
chances mainly from Las Vegas north and breezy to windy conditions
over the deserts. The next storm should be approaching the West
Coast Sunday afternoon, but as was the case yesterday, the models
disagree on whether this storm will be another quick moving weak
trough or will deepen and slow down as it moves inland. By Monday
night, model solutions range from shortwave ridging over our area to
a cold closed low overhead. Chose to make no changes for Monday and
Tuesday due to a lack of confidence in any one pattern evolution.

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



Short Term/Aviation...Salmen
Long Term...Morgan

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