126
FXUS65 KVEF 060421
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
921 PM PDT Sat Sep 5 2026

.KEY MESSAGES...

* Shower and thunderstorm chances increase across the Mojave Desert
  on Sunday as moisture surges northward.

* Drier conditions expected for Labor Day, though monsoonal
  moisture and warmer temperatures return midweek.

&&

.DISCUSSION...Today through Friday.

The primary forecast concern involves a moisture surge from
Hurricane Marie, currently located several hundred miles off the
southern tip of the Baja Peninsula. Southwesterly flow aloft over
the southwestern United States will draw moisture from the system
into the region, bringing PWATs into the 1.0 to 1.5 inch range. The
approach of a 500 mb perturbation in the flow pattern supports the
development of a band of precipitation stretching southwest to
northeast along the Interstate 15 corridor. However, a slight shift
to the north or south could bring much higher precipitation amounts
to otherwise dry areas. Widespread cloud cover and the early morning
timing of the mid-level perturbation support widespread stratiform
precipitation rather than convective thunderstorms. Flow
perpendicular to certain mountain ranges is an excellent setup for
orographic lift and the greatest precipitation totals are expected
over high terrain. On the Spring Mountains, there is a 70 percent
chance or greater of one inch of precipitation over 24 hours over
8,000 feet in elevation and a 30 percent chance of two inches of
precipitation. Totals in the Las Vegas Valley will be far lighter,
but there is a 20 to 40 percent chance of at least one quarter inch
of rain in 24 hours. Roadway ponding and running washes are possible
across much of the Mojave Desert. Precipitation should end on Sunday
night as the disturbance moves inland.

Warmer and drier conditions are expected on Labor Day as heights
aloft start to increase again. High pressure will continue to build
and move west through the workweek. The position and strength of the
high will affect how much moisture is is able to draw into the
western United States, from both tropical systems and traditional
monsoonal sources. Temperatures are also dependent on precipitation
and cloud cover, but rising heights aloft should generally send
highs back towards normal values for early September.

&&

.AVIATION...For Harry Reid...For the 06Z Forecast Package...
Southwest winds of 10 knots or less are expected through the
overnight period. Expect gradually increasing cloud cover through
the night with bases lowering to less than 10kft AGL by mid-morning.
Shower chances will develop as early as 12Z, but will become more
likely after 15Z, with the potential for light to moderate rain from
15Z through 00Z. CIGs will generally remain between 7kft and 9kft
AGL, but could drop to around 5kft AGL at times during the
afternoon, along with a 10 percent chance of visibility reductions
to less than 6SM. Isolated convection is also possible, mainly at
the onset of precipitation. Showers will end Sunday evening, with
gradually improving ceilings overnight into Monday morning.
Temperatures will remain below 100F through at least Tuesday.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 06Z Forecast Package...Expect gradually
increasing cloud cover overnight from southwest to northeast, with
CIGs falling to 8kft to 12kft by morning for all the TAF sites
except KBIH, where SCT high clouds are expected. Shower chances will
start to increase after 12Z across the western Mojave Desert and by
15Z across southern Nevada. CIGs will generally remain around 10kft
AGL, but may lower to between 4kft and 6kft AGL with some heavier
showers through the day. There is also a 10% chance of visibility
reductions to less than 6SM. Isolated areas of convection are also
possible, especially at the onset of precipitation. The
precipitation will end from southwest to northeast Sunday evening,
with gradually improving ceilings overnight into Monday morning.

&&

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

&&

$$

DISCUSSION...Meltzer
AVIATION...Planz

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