Area Forecast Discussion
Issued by NWS Las Vegas, NV

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293
FXUS65 KVEF 292136
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
233 PM PDT THU SEP 29 2016

.SYNOPSIS...Isolated showers and thunderstorms are
expected across Mohave County tonight while the rest of the area
will be mostly clear. On Friday, showers will be much more limited
as drier air begins to move into the area ahead of a trough.
However, the trough will provide gusty winds across the area this
weekend and into Monday. Temperatures will be slightly above normal
through Saturday but will plummet 15 to 20 degrees by Monday.
&&

.DISCUSSION...

Isolated thunderstorms confined to the terrain of central and
northern Mohave County this afternoon. Warm air aloft indicated on
the Las Vegas 12z sounding looks to have been enough to cap
convection over the terrain of southern Nevada with only some weak
radar returns over Lincoln County. Have removed or lowered POPs
across the terrain of eastern California and southern Nevada this
evening leaving the highest coverage in across Mohave County.

Can not rule out a few light showers throughout the night over
Mohave County due to an elongated weak vorticity lobe associated with
an upper disturbance moving through western Arizona.

On Friday...Increasing southwest flow aloft ahead of a trough
approaching the Pacific Northwest Coast will start spreading drier
air into the far western areas while just enough
moisture/instability remains over Mohave County to limit an
precipitation chances to the terrain of central and northern Mohave
County.

Saturday - Monday...An initial shortwave ejecting out of the trough
across northern California/northwest Nevada Saturday will help
strengthen west-southwest surface winds which in turn spread drier
air east encompassing the entire southern Great Basin and Mojave
Desert. Winds on Saturday look to remain well below advisory
thresholds. A deeper/colder upper low is progged to dig into
northern California Sunday. Tightening surface pressure
gradient/thermal gradient as well as stronger winds aloft will make
for a windy Sunday. Latest 9km run paints highest winds over
northwest San Bernardino, southern Inyo, southern Nye and Lincoln
Counties. Also, there are signs of downslope winds possibly in the
lee of the southern Sierra Nevada. A wind headline for parts of the
region look likely. Trough progged to dig southeast through southern
Nevada Sunday night-Monday pushing a strong cold front through the
region. Strong pre-frontal west-southwest winds continue Sunday
night before going northwest Monday. Wind headlines likely to
continue through Monday especially from Esmeralda, Nye and Inyo
Counties under strong northwest flow. Something to watch...Models
look to be trending deeper and slower with incoming trough. This was
the case with the 12z GFS painting some light QPF as far south as
the Spring Mountains. We already has POPS in for the southern Sierra
Nevada and terrain of Lincoln County so did introduce a slight
chance for the Spring Mountains. It will be a quick hitter but snow
level are forecast to plummet to between 6500-7000 feet in the
southern Sierra Nevada and down to 7500 feet for the Spring
Mtns/Sheep Range. As one can image temperatures will fall
dramatically as well with highs some 10-15 degrees below normal
Monday.

A few spots will likely start Tuesday at or slightly below freezing
as the area gets its first taste of Fall. Tuesday-Thursday will be
dry with temperatures gradually moderating under a dry west-
northwest flow aloft.
&&

.AVIATION...For McCarran...Southeast winds of 5-10 kts will continue
through 00z before decreasing and eventually turning to the south-
southwest after sunset. CIGS are expected to remain AOA 10k feet,
with showers mainly confined to the mountains and Peach Springs
corridor. However, a stray shower cannot be ruled out in the valley.
Similar wind conditions are expected Friday, with fewer showers.
Increasing southwest winds are expected over the weekend. Gust of 20-
30kts are expected Saturday, and 25-35kts on Sunday along with areas
of mechanical turbulence, especially near the mountains.

For the rest of southern Nevada...northwest Arizona...and southeast
California...Scattered showers and isolated thunderstorms into this
evening over the higher terrain of Clark, Lincoln, Mohave and Inyo
Counties. Expect gusty winds near any shower activity. Outside of
showers, light south to southeast winds will common today. South to
southwest winds will begin to increase in areas northwest of the I-
15 corridor Friday, then area wide on Saturday and Sunday. Sunday
will see the strongest winds, with widespread gusts 25-35kts
(stronger near the high terrain), and areas of blowing dust and
mechanical turbulence.
&&

.FIRE WEATHER...On Saturday, breezy conditions combined with low
afternoon RH`s will favor some localized red flag conditions but
coverage doesn`t appear widespread at the moment. On Sunday...winds
will increase further and favor a period of critical fire weather
and widespread Red Flag conditions Sunday into Sunday evening.
Even though temperatures are expected to plummet Monday, localized
Red Flag conditions could potential continue under a dry northwest
flow. The first dusting of snow is possible above 8000 feet as a
cold upper low moves through the area Sunday night and Monday.
Improving conditions are expected Tuesday-Thursday of next week
under a dry west-northwest flow aloft.
&&

.SPOTTER INFORMATION STATEMENT...Spotters activation will not be
needed. Strong winds are expected to develop Sunday and continue
through Monday. Spotters are encouraged to report according to
standard operating procedures.
&&

$$

Discussion/Fire Weather...Pierce
Aviation...Wolcott

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