972
FXUS65 KVEF 280430
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
930 PM PDT Sun Sep 27 2026

.KEY MESSAGES...

* Increased chances for showers and thunderstorms arrive Monday
  and Tuesday along with cooler temperatures.

* Stronger storms across the Colorado River Valley and northwest
  Arizona may produce flash flooding, small hail, and strong wind
  gusts.

* Mild weather and warming temperatures are expected during the
  second half of the week.

&&

.DISCUSSION...through next weekend.

Afternoon satellite imagery depicts a deepening West Coast trough
digging southward into northern California. Meanwhile, remnant
mid and high level moisture from Tropical Storm Odalys continue to
stream northward into the Southwestern US, with a broad cloud
shield and some light shower activity developing as far north as
the Las Vegas Valley. These two features will work together over
the coming 48 hours to produce widespread unsettled conditions,
and pockets of heavy rainfall mainly south and east of the I-15
corridor through Tuesday evening. In the meantime, light showers
and localized gusty winds will remain possible through the evening
across southern Nevada associated with increasing moisture above
a dry sub-cloud layer. With DCAPE values of 1000-1500 across the
region, some gusts exceeding 40 mph will be possible, and the KLAS
airport recently gusted to 45 mph as some weak showers moved
overhead.

Moisture will continue to stream northward overnight with light
stratiform precipitation expanding in coverage across Northwest
Arizona and the southern reaches of the Colorado River Valley.
This precip shield will largely be associated with moisture
streaming northward from Tropical Storm Odalys, and will shift
eastward through the day on Monday. Meanwhile, an incoming trough
will approach from northern California through the afternoon
resulting in an increasingly diffluent flow aloft along with
steepening lapse rates as the mid-levels cool. This will result
in expanding instability across the Colorado River Valley and
Northwest Arizona through the afternoon hours. Todays high
resolution guidance continues to struggle on how far west to
initiate convection, but most of the convective allowing models
favor areas near or just east of Las Vegas as the initial storm
development focus area, with activity expanding into the river
valley and northwest AZ through the afternoon and evening hours.
Given the dynamic forcing involved with the incoming low, and
strong southwesterly wind shear, a few severe storms with hail to
quarter size and gusty surface winds will be possible.

Training storms producing pockets of intense rainfall can also be
expected given the deep layer southwesterly shear present ahead
of the incoming low. Given this, the presence of some transient
tropical moisture, and agreement of CAM guidance - expanded the
Flood Watch to include the Colorado River Valley and far southern
Clark County. A few weak showers and storms may also form closer
to the low center across the Sierra and Great Basin, but are not
expected to be of significant impact.

Moisture will wrap around the low as it moves into Arizona on
Tuesday with lingering showers expected across southern Nevada and
northwest Arizona. By Wednesday, the low will shift east with low
amplitude high pressure building back in and a warming trend
commencing.

&&

.AVIATION...For Harry Reid...For the 06Z Forecast Package...South to
southwest winds will remain elevated between 8 and 12kts overnight,
with a few gusts to 18 knots lingering through midnight. A similar
daily wind pattern is expected again Monday, with speeds and gusts
slightly lower than today. VCTS is included after 19Z Monday, with a
PROB30 group from 20Z to 02Z to account for increasing confidence in
convective development. Convection in the vicinity of the terminal
may linger into Monday night, although the most significant impacts
will likely shift east of the terminal area after sunset. Any storms
Monday will have the capability to produce strong winds with erratic
directions, heavy rain, lightning, and lower ceilings.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 06Z Forecast Package...Typical diurnal wind
patterns will continue overnight, with speeds in most areas
remaining less than 12 knots. The exception will be across the
western Mojave Desert, including KDAG, where elevated south to
southwest winds will continue for several more hours. Light shower
activity is expected through the night around KEED and KIFP. More
widespread convection is likely Monday afternoon and evening across
southern Nevada, northwest Arizona and southern and eastern San
Bernardino counties. CIGs through the TAF period will generally
remain SCT-BKN AOA 15kft AGL, although CIGs down to 10kft AGL are
possible with shower activity. Any storms Monday will have the
capability to produce strong winds with erratic directions, heavy
rain, lightning, and lower ceilings.


&&

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

&&

$$

DISCUSSION...Outler
AVIATION...Planz

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