162
FXUS65 KVEF 202333
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
433 PM PDT Tue Oct 20 2026

.KEY MESSAGES...

* Multiple rounds of rain and storms expected over the Sierra, Lower
  Great Basin and NW Arizona this afternoon through Thursday. Flash
  Flooding possible under repeated storm activity.

* Increasing confidence for a dry conditions and seasonable
  temperatures this weekend.

&&

.DISCUSSION...Today through Next Monday.

An active weather pattern is setting up for the Desert Southwest
this week as a strong trough slowly approaches the west coast
impacting local weather through the end of the week. For this
afternoon and tonight, mainly dry conditions expected for most
desert valleys while the first round of the thunderstorms is
expected over Inyo, southern Nye, and Esmeralda counties...more
isolated convection possible in higher terrain further east. The
entire area remains ahead of the approaching trough with strong
upper level diffluence and enhanced lift from the left exit region
of a 100 kt jet streak. Moisture advection northward is great for
this time of year with PW of 0.7-1.00 inches engulfing the area.
MUCAPE of 300-700 j/kg combined with 0-6km shear exceeding 50 kt
will be more than sufficient for more organized clusters of showers
and storms. DCAPE values 800-1000+ j/kg may also lead to a localized
strong wind threat in a few storms this afternoon and evening on top
of the heavy rain threat. Best forcing for ascent will be in the
higher terrain of Inyo county and Death Valley, Southern and Western
Nye County and Esmeralda County. At the moment confidence is not
high enough in a widespread Flash Flood threat to warrant the
issuance of any type of watch, however a low threat does exist in
areas that see repeated rounds of storms. Lingering lighter shower
activity may persist into the night due to such strong lift and
upper level dynamics

For Wednesday the upper level low will be approaching the Central
California Coast. Precipitation chances are higher across the board
due to additional moisture and colder air aloft, but the same places
will be favored in addition to Mohave County. A strong southerly
50kt low to mid level jet sets up bringing copious amounts of
moisture northward into NW Arizona. As waves of energy rotate around
the trough and into the region, expect showers and storms to begin
developing early Wednesday morning across Mohave County and
potentially Inyo and Esmeralda counties, with the most robust
convection likely during the afternoon hours. Shear, instability,
and moisture will be similar if not better than parameters on
Tuesday, resulting in the same threat...flash flooding, gusty winds,
heavy rain, and lightning. Highest confidence in any Flash Flooding
is currently over Northern Mohave County where better lift and
moisture availability should result in more robust storms; Therefore
a Flash Flood Watch has been issued for that area Wednesday and
Thursday. While showers and storms are expected Wednesday afternoon
over Inyo, Esmeralda, and Nye counties, more isolated convective
coverage should keep the flash flood threat lower. Outside of any
convection, most of the Mohave Desert and its valleys should be
fairly warm and dry with temperatures a few degrees above normal for
this time of year.

Finally on Thursday, the upper low shifts inland into Central
California and Nevada with the main vort max bringing widespread
threat of showers and storms to much of the Lower great basin. Steep
lapse rates and sufficient instability from cold air advection aloft
will allow for convective showers and a few storms through the day
on Thursday. This will likely be the best chance for any rainfall in
the Mojave Desert valleys; however guidance has been consistent in
showing a dry slot associated with the incoming trough keeping the
majority of the precipitation away from the Mohave Desert and
Colorado River Valley with a 40-70% chance of 0.10" of rain or less.
Overall, best odds of precipitation impacts are in the southern
Great Basin, Inyo County, and northern Mohave County where higher
chances of total rainfall 1.00" exist. Outside of any storms, gusty
south-southwest winds (20-40 mph) will accompany this system as well
Thursday and Friday, but any impacts should be confined to the local
lakes. Temperatures drop about 10 degrees from earlier in the week
with widespread highs Thursday into the weekend in the 70s for
desert valleys.

There is a minor wintry component of this system as snow levels
bottom out around 8kft in the Sierra. However, precipitation will
largely be done by the time colder air filters in , so any impacts
are expected to be confined to elevations above 9kft where forecast
snow totals range from 3-10" (the higher amounts near the crest).

By Saturday, ensemble guidance has the area firmly on the backside
of the trough with a dry northerly flow that quickly scours out
moisture and precipitation chances, and produces some gusty north
winds. On Sunday and Monday, the flow weakens and becomes more zonal
or southwesterly, keeping us dry with light winds and slightly below-
normal temperatures.
&&


.AVIATION...For Harry Reid...For the 00Z Forecast Package...Winds
will continue to be generally light and diurnal through the day,
with light-to-breezy southeasterly winds this afternoon around 8 kts
and light southwesterly winds overnight. Gusty south-southeasterly
winds pick up Wednesday afternoon with gust speeds topping out
between 25 and 30 kts. FEW-SCT aoa 10 kft through the TAF period.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 00Z Forecast Package...Light and diurnal winds
in the Las Vegas Valley and Colorado River Valley continue through
the day today, with gusty south-southeasterly winds picking up
Wednesday afternoon to 30 kts. KBIH will continue to gust from the
south-southeast this afternoon and Wednesday afternoon to 30 kts
with the potential for gusts from variable directions due to
vicinity thunderstorms. 30 percent chance of showers and
thunderstorms over the KBIH terminal, with best chances between 01
and 05Z. Gusty east winds at KDAG to 25 kts this afternoon and
Wednesday afternoon. FEW-SCT aoa 10 kft, though expect BKN aoa 8 kft
with thunderstorm activity overhead.
&&


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

&&

$$

DISCUSSION...Moore
AVIATION...Soulat

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NWS Las Vegas (VEF) Office