558
FXUS65 KVEF 281020
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
320 AM PDT Mon Sep 28 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.

Early morning satellite imagery shows tropical moisture streaming
across the southeastern portion of our forecast area while a trough
digs along the coast of California, beginning to move inland. This
trough will move through the region today and tomorrow, bringing
increased precipitation chances to southern Nevada, southeastern
California, and northwestern Arizona. As this trough interacts with
the tropical moisture, scattered-to-widespread showers and
thunderstorms capable of producing heavy rain are expected across
the eastern half of our forecast area. The northwestern portion of
our forecast area will see increased chances for isolated showers
and thunderstorms, mainly in areas of higher terrain. Since moisture
in the northwestern portion of our forecast area will not be as
abundant, precipitation will be on the lighter-to-moderate side.
Gusty outflow winds, lightning, and small hail (graupel) will be
possible with these storms in the northwestern portion of our
forecast area this afternoon.

The eastern half our forecast area will see an elevated flash flood
risk today as the dynamics from the aforementioned trough work with
the anomalous tropical moisture to fuel showers and thunderstorms
across the area. The highest risk of flash flooding will be in
northwestern Arizona, where the Weather Prediction Center (WPC) has
highlighted Mohave County with a Moderate (Level 3 of 4) Excessive
Rainfall Outlook (ERO), and southern Nevada and the Colorado River
Valley where WPC has placed a Slight ERO (Level 2 of 4). Light
precipitation is already ongoing across southeastern Mohave County,
with anywhere from a few hundredths to 0.20 inches of rain having
fallen. This band of lighter showers will continue into the early
morning hours, with stronger showers and thunderstorms developing
across Lincoln and Mohave Counties later this morning. Mohave County
will see nearly continuous storm activity today. Additional
development will occur across southern Nevada and eastern San
Bernardino County during the afternoon and evening. HiRes models
have consistently highlighted the potential (30 to 50% chance) for
storms capable of producing rain rates in excess of an inch per hour
across southern Nevada into the lower Colorado River Valley late
this afternoon into the evening hours. Given the near continuous
storms expected in Mohave County and the potential for very heavy
rain across southern Nevada and the Colorado River Valley, a Flood
Watch will go into effect at 5:00 am MST/PDT. On Tuesday, additional
showers and thunderstorms will be possible across the eastern half
of our forecast area as the trough axis swings through and moisture
wraps around the low.

The low will move east of the area by Wednesday, taking moisture and
precipitation chances along with it. High pressure will build over
the region through the rest of the week and promote a warming and
drying trend. Highs reach near normal values on Thursday, then
generally remain steady through the rest of the week. This includes
highs in the low to mid 90s in Las Vegas, upper 80s to low 90s in
the Owens Valley, and in the upper 90s in the Colorado River Valley.
The high will support lighter winds areawide as well.

&&

.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...Meltzer/Stessman
AVIATION...Planz

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