Flash Flooding and Dust Storm in Arizona, September 2 to 6, 2025

Area Forecast Discussion
National Weather Service Las Vegas NV
357 PM PDT Tue Sep 2 2025

.KEY MESSAGES...

* Monsoonal moisture will provide fuel for widespread shower and
  thunderstorm activity today. Flash flooding is the primary concern.

* Moisture remains in place through midweek before slowly scouring
  out of the region, shifting precipitation chances further east
  each day.

&&

.DISCUSSION...

The ridge of high pressure over the Desert Southwest is shifting
slightly eastward, as a result of a shortwave approaching off the
California coast. This is allowing additional moisture into the
area, providing fuel for widespread thunderstorm activity. Dewpoint
rose from the upper 30s to lower-mid 60s across southern portions of
the CWA as storms moved into the area on the heels of a monsoonal
easterly wave propagating from souther Arizona. Storms have produced
strong winds along the periphery of the cloud shield and extended
outflow boundaries, which have provided focus for short-lived storms
as the outflow moved through. There have been brief periods of heavy
rain, but most areas have seen less than .10" of rain with a few
areas of .25" to .35". Clearing this afternoon will allow for a
resurgence of thunderstorm activity, as is being seen in Mohave and
Coconino counties in Arizona. Assuming the clearing continues,
thunderstorms could impact the Las Vegas Valley by the early evening
hours. While storms have been moving fairly quickly, the amount of
available moisture will support high rain rates of over 2" per hour,
meaning stronger storms could cause flooding rapidly. Due to this,
there is a Flash Flood Watch in effect through the 1 AM Wednesday
morning.

A Shortwave moving northward into will linger around the are for the
next several days, keeping an opportunity for showers and
thunderstorms areawide. The area will slowly dry out from west to
east as this shortwave slowly translates eastward and shifts dynamic
support for thunderstorms into Utah and Arizona. Lingering moisture
will keep mountain showers around into the weekend, but coverage
will be much less by then.

&&

.AVIATION...For Harry Reid...For the 00Z Forecast Package...
A complex forecast is in store for much of the Las Vegas Valley
region. Thunderstorms storms currently in Mohave County will
continue to work their way to the west into the early evening. These
storms will impact the Las Vegas Valley between 01Z and 03Z either
directly or with gusty outflow winds. Additional shower and storm
activity will likely linger into the overnight hours. By 10z-12z,
activity should wane with scattered to overcast mid level ceilings.
Temperatures are not forecast to reach 100 on Wednesday. Additional
showers and/or thunderstorms are possible on Wednesday but exact
timing and location are uncertain but will favor the late afternoon
and evening hours.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 00Z Forecast Package...A complex forecast is in
store with scattered showers/storms ongoing and more expected into
the evening and particularly across southern Nevada during the
overnight hours. Winds with thunderstorms will produce strong gusty
outflow winds, favoring the Colorado River and Las Vegas Valley
terminals this evening. A mostly diurnal wind pattern is expected at
KBIH, further removed from evening showers and storms. Another round
of showers and thunderstorms on Wednesday afternoon and evening will
favor terminals in southern Nevada and northwest Arizona. Broken to
overcast mid level ceilings can be expected through most of the
period.
&&

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

&&

DISCUSSION...Berc
AVIATION...Czyzyk

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