155
FXUS65 KVEF 152004
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
104 PM PDT Sun Sep 15 2024

.SYNOPSIS...A large low pressure system dropping down from the
northwest into California and Nevada will bring widespread gusty
south to southwest winds to the region today through Monday along
with a significant cooling trend. A second trough of low pressure
will move across the area midweek bringing a reinforcing shot of
cool air along with scattered showers.
&&

.SHORT TERM...Through Tuesday night.

A potent upper level system is expected to drop into the region
tonight and Monday. Not much changes overall synoptically with this
system with strength and timing well collaborated across models.

Widespread gusty winds will be the main impact with this system that
most people will see. No changes were made to the wind headlines as
the timing and impact levels remain on track from previous
forecasts. The strongest winds are expected tonight in Inyo County
and Esmeralda County, then Monday afternoon for areas further east.
South to southwest winds will gust 40-50 MPH with the strongest
winds starting tonight in western portions then spreading east by
Monday late morning. Areas of blowing dust could also impact areas as
the winds ramp up. WInds will diminish Monday night as the upper
level system pushes east away from the area. With height falls and a
cooler airmass moving in with the approaching low, temperatures will
drop. High temperatures on Monday will be about 10-15 degrees cooler
than today.

Also watching the potential for precipitation impacts as the upper
level trough pivots into a neutral position and briefly sits over
northern California Monday. Strong forcing will develop around the
center of the low which will allow for precipitation to develop in
parts of northern Inyo County into Esmeralda and central Nye
County. With little movement of the low and its associated area of
strongest lift, continuous rainfall is expected Monday morning
through the early afternoon. Modest moisture will be available as
the trough moves in as PWATs around 0.50-0.75 inch set up across the
region. HREF continues to highlight Esmeralda County with the
highest risk for rainfall impacts with a 10%-30% probability for 3
hour rainfall amounts over 1 inch, mainly Monday morning. This would
be the area closest to the trough axis and thus will see the
strongest and longest duration of forcing. WPC has that area in a
slight risk for excessive rainfall with isolated flash flooding
possible, which is reasonable given the amount of forcing, available
moisture, and the flashy nature of that area. Rainfall with be
heaviest 5AM through about 11AM before the center of the low shifts
eastward. About 0.50 inch of rainfall totals are likely in Esmeralda
County, with the wettest solutions across the ensembles suggesting
high end potential amounts of 0.75-1.00 inch rainfall totals. While
the forcing will spread east as the low shifts, the available
moisture and duration will limit precipitation impacts further east.
Ensembles show little to no probabilities for impactful
precipitation across the Southern Great Basin where scattered
showers could develop Monday afternoon. Further south, it will
remain dry as better forcing will remain to the north.

The trough axis will pass the region Monday night, with dry
anticyclonic flow setting up behind it. Precipitation will diminish
as the trough shifts east and by Tuesday morning, it will be dry
across the region. With northwest winds aloft pushing cooler air
into the region, it will be cool Tuesday with high temperatures
remaining about 10 degrees below normal. Winds near the surface will
be lighter on Tuesday as the upper level system moves away from the
area and the pressure gradient decreases. Impactful winds are not
likely (below 20% probability) for Tuesday.



.LONG TERM...Wednesday through Saturday

Lighter winds are expected Wednesday through the end of the week
as the tight pressure gradient and low level jet moves east along
with the trough. However, the system will leave cold air over the
region in its wake. Morning lows will be 10 to 15 degrees below
normal for mid September. Another deep low will drop down from the
Pacific Northwest into the Great Basin midweek. It should provide
some reenforcement for cool temperatures, keeping highs around 10
degrees below normal through the end of the workweek. Some
guidance is not showing a strong wind signal with this system, but
others highlight the potential for elevated winds. This will
depend on the placement of the trough and where the tightest
pressure gradient will form. Lastly, moisture advection with the
system will bring increased precipitation chances midweek,
particularly in the southern Great Basin. As this system exits
towards the end of the week, Pacific high pressure moves in behind
it and should boost temperatures for next weekend.


&&

.AVIATION...For Harry Reid...Gusty southerly winds can be expected
at the terminal through Monday afternoon.  While winds should settle
around 220 to 240 degrees by 22Z, some variability is likely before
then, with winds possibly backing to the east as far as 160 degrees.
 Sustained winds of 15 to 20 knots are likely, and there is a 60
percent chance of seeing an occasional gust to 30 knots after 22Z.
Winds will diminish overnight, but occasional gusts to 15 knots will
still be possible.  The elevated southwest winds will continue
Monday with gusts over 30 knots likely through the afternoon. VFR
conditions will continue through Monday with only a few clouds with
bases AOA 10kft expected.

For the rest of southern Nevada, northwest Arizona and southeast
California...Breezy south-to-west winds will continue across the
area into this evening, with gusts of 20 to 30 knots likely at area
TAF sites.  Some decrease in winds is expected after sunset, but
occasional gusts to 20 knots will continue overnight.  Winds will
increase again on Monday with gusts as high as 40 knots possible
over the western Mojave Desert, including KDAG.  Gusts of 30 to 25
knots are likely elsewhere.  Hazy skies due to the wildfires over
southern California can still be expected over the western Mohave
desert today, possibly spreading into the lower Colorado River
Valley overnight.  However, visibilities should remain greater than
6NM in all areas.  Otherwise, no significant cloud cover is
expected, except at KBIH, where SCT-BKN clouds with bases AOA 10kft
are possible.
&&

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

&&

$$

SHORT TERM...Nickerson
LONG TERM...Meltzer
AVIATION...Planz

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