Heat in Nevada, September 1 to 2, 2024

Area Forecast Discussion
National Weather Service Las Vegas NV
822 PM PDT Sat Aug 31 2024

.SYNOPSIS...Modest monsoonal moisture will return precipitation
chances to northwestern Arizona as well as the mountains of far
southeastern California and southern Nevada today, with chances
dwindling, but not fully disappearing in Mohave County through the
upcoming week. Expect temperatures about five degrees above early
September normals.
&&

.UPDATE...This afternoon's convection has begun to wind down across
the area. Central Mohave County saw the most widespread measurable
precipitation this afternoon with most rain gauges recording 0.04 to
0.08 inches and a few isolated gauges picking up 0.25 to 0.50 inches
with the more intense cells. Locally here in Las Vegas, the Seven
Hills/Anthem area and Henderson were our big precipitation winners
with a handful of gauges picking up 0.04 to 0.16 inches. As
expected, storms over Mohave County kicked out 30 to 40 mph easterly
outflow winds, which impacted Lakes Mead and Mohave earlier this
afternoon. Another round of afternoon showers and thunderstorms is
expected in Mohave County and the higher terrain of Lincoln and
Clark Counties. Similar to today, the primary threats with any
storms that develop will be lightning, gusty outflow winds, and
moderate-to-heavy rain. Unlike today, HiRes models show a lesser
risk for outflow winds and thunderstorms impacting the area lakes.
However, boaters should still take care to remain weather aware as
conditions can change quickly during monsoon season.
&&

.SHORT TERM...through Sunday night. Late morning satellite loop was
interesting. Very shallow convection, producing sprinkles and virga,
was tracking northwest through western Lincoln and central Nye,
associated with the weak shortwave trough. Deeper convection was
beginning to pop from eastern Lincoln down into northeast San
Bernardino and northern Mohave, associated with daytime heating and
orographic lift. A few lightning strikes had been noted over
northern Mohave. These storms are expected to increase in coverage
and intensity as the afternoon wears on, eventually leading to the
biggest forecast problem of the day - will storms congeal over
Mohave County and eject an outflow boundary westward across the
Colorado River, or northwest toward Las Vegas? As should be
expected, the exact evolution of these storms changes with each high
res model run, so confidence in details is low, but moderate in the
overall idea of storms congealing and shooting outflow winds
somewhere. Liked the mid shift's wind forecast grids for the
afternoon and evening so much that we did not change them. Storms
should dissipate shortly after sunset as heating is lost and cool
outflow winds choke off any unstable inflow. Overall trends for
tomorrow suggest no more shortwave trough forcing and slightly
higher mid level heights and temperatures, which should result in
less (not no) thunderstorm coverage Sunday vs today. Overall, high
temperatures Sunday should change little from today, although some
points will see big swings if they get early thunderstorm
development one day and not the other.

.LONG TERM...Monday through next Weekend.

A shortwave will lift northwest through northern California and
Nevada Monday and Tuesday next week. Dry air will be pumped into the
region as the flow turns west which will decrease precipitation
chances. There is a very low chance (20%) Monday afternoon for
showers and thunderstorms in eastern Mohave County. By Tuesday,
precipitation chances end across the region. It will then be dry
through the rest of the week as high pressure builds.

As the shortwave moves into the region Monday, the pressure gradient
will increase in parts of the southern Great Basin. The probability
for impactful wind gusts over 40 MPH remains very low (20% of
less) outside of the terrain in Inyo, Esmeralda, and Nye
counties. So not expecting widespread wind impacts Monday. The
probabilities for wind speeds that would be concerning for
wildfire starts and spread is high in that same region, around
40%-60%. With significant dry air in place over the region, will
need to watch for the need for Red Flag Warnings if fuels are of
concern.

With heights building over the region, temperatures will increase
through the week. Above normal temperatures are likely areawide
by Wednesday and will continue through the weekend. Heat risk will
climb to "High" or "Extreme" levels for most valley locations
outside of the southern Great Basin and Owens Valley for the
second half of next week.
&&

.AVIATION...For Harry Reid...Winds will generally remain under
8kts for much of the afternoon and favor an east to southeast
direction. There will be a few thunderstorms forming over the higher
terrain surrounding the valley and it is possible that we could see
an outflow boundary make it to the terminal this afternoon, however,
with storms developing over northwest Arizona, some of the models
are indicating an outflow boundary pushing west and reaching the Las
Vegas Valley between 01-03z this evening. If that occurs, we could
see east to southeast winds between 15-25kts and possibly higher.
Outside of any storms, we can expected to see FEW-SCT clouds around
12k feet.

For the rest of southern Nevada, northwest Arizona and southeast
California...Diurnal winds with speeds of less than 10 knots are
expected through Sunday. The primary weather concern is shower and
thunderstorm development this afternoon and evening. Showers may
develop in northwest Arizona in the vicinity of KEED and KIFP, and
gusty easterly to southeasterly winds may reach these terminals
along with the Las Vegas Valley terminals. Convection may also occur
along high terrain around the Las Vegas Valley, but any showers or
thunderstorms that form should remain outside of the forecast area.
Outside of storms, FEW to SCT mid and high level clouds stream
across the area through the forecast period.

Similar conditions are expected Sunday, but overall thunderstorm
coverage is forecast to be lower and mainly confined to northwest
Arizona. Still, gusty outflow winds will be possible near any storms.
&&

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

UPDATE...Stessman
SHORT TERM...Morgan
LONG TERM...Nickerson
AVIATION...Gorelow

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