Severe Thunderstorm Warning 63, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
1238 PM PDT Fri Sep 26 2025

.KEY MESSAGES...

* Chances of showers and thunderstorms are in this weekend's
  forecast for southern Nevada, southeastern California, and
  northwestern Arizona.

* Moisture gradually scours out of the region through the work week,
  with a fall-like pattern bringing below-normal temperatures and
  breezy afternoons.

&&

.DISCUSSION...Through Thursday

A cutoff upper level low, currently centered north of Twentynine
Palms, will be the main driver of weather this weekend. Plentiful
moisture along with forcing from the low has already set off
thunderstorm activity early this morning over northwestern Arizona.
One storm produced a gust of 67 mph at 6 AM PDT in Nye County. This
activity should ramp up this afternoon with the introduction of
surface heating, particularly in regions along and south of
Interstate 15. However, this early morning activity may hinder
development later today due to leftover cloud cover and exhausted
atmospheric instability. CAMs have also backed off, pushing the more
active period into the early afternoon rather than late morning.
Heavy rainfall, gusty outflow winds, and small hail are all
possibilities with the strongest storms. The position of the low
becomes favorable for moisture advection on Saturday, sending PWATs
into the 0.75 to 1.50 inch range. The result will be more widespread
POPs and an increased concern for heavy rainfall and flash flooding.
The primary areas to watch for flash flooding are southern San
Bernardino and southern Mohave counties.

The upper level low will track east through Arizona on Sunday,
leading to a reduction in moisture and precipitation potential. The
greatest chances appear to be in northwestern Arizona and far
eastern Nevada, where forcing from the weakening low and lingering
moisture may kick off storms in the afternoon. Dry southwesterly
flow will take its place through the workweek as an upper level
trough moves into the Pacific Northwest. There is some uncertainty
in whether remnant moisture from Hurricane Narda will make it into
the flow, but if it does, POPs linger into Monday and Tuesday.
Outside of precipitation, lower heights aloft allow for below
average temperatures through most of the week.

&&

.AVIATION...For Harry Reid...For the 18Z Forecast
Package...Thunderstorms are the main concern again this forecast
period. Storm activity should increase later today in Arizona and
southern Nevada, then track northwest. This includes the Mormon
Mesa and Peach Springs corridors. Although the most favorable time
for storms reaching the terminal is 20Z to 00Z this afternoon,
cloud cover from earlier storms may inhibit development later in
the day. The primary threats with any storms that develop will be
rain, lower CIGS, lightning, and variable gusty outflow winds.
Outside of any convective influence, winds will remain relatively
light, 10 knots or less, and will follow typical diurnal
directional trends.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 18Z Forecast Package...Thunderstorms will be
the main concern again this forecast period. The best chances for
storms will be south and east of the Interstate 15 corridor.
Activity is ongoing in northwestern Arizona and southern Nevada and
should move northwest through the rest of the morning and afternoon.
However, clouds left over from earlier convection may inhibit
additional storm development later today. Some storms should also
reach southeastern California during the afternoon and evening. The
main concerns with storms will be erratic gusty winds, heavy rain,
and low ceilings with terrain obscuration. Away from storms, winds
follow diurnal trends with speeds of less than 12 knots.

&&

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

&&

DISCUSSION/AVIATION...Meltzer

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