596
FXUS65 KVEF 170317
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
817 PM PDT Fri Aug 16 2024

.SYNOPSIS...Dry and breezy conditions can be expected across the
Western Mojave Desert and Western Great Basin through the weekend.
This will be contrasted with increasing moisture and thunderstorm
activity across the eastern Mojave Desert and northwest Arizona,
with locally heavy rainfall possible Saturday in northern Mohave
County. Monsoon storms will tend to retreat into Arizona early
next week before creeping back west midweek onward. Temperatures
will remain a few degrees above normal through the period.

&&

.UPDATE...High clouds and moisture continue to move in this evening
as an inverted trough lifts north through SE California. This
feature brings 20-40% rain chances to Clark, Mohave, and eastern Nye
Counties early tomorrow morning, while Lincoln County has 30-60%
chances throughout most of the morning hours. After this first wave,
attention turns to eastern portions of our area in anticipation of
afternoon redevelopment. Main area of concern is northern Mohave
County, where a Flash Flood Watch is in effect through Saturday
evening. In addition to the flood potential, anomalous vertical wind
shear (~30-40 knots) will increase the likelihood of strong to
severe storms, with damaging winds and small hail possible. Storm
chances linger across SE Nevada and NW Arizona on Sunday, before
getting pushed to the eastern fringes of our area next week as drier
air moves in.

&&

.SHORT TERM...through Sunday night.

Interesting forecast pattern for the upcoming 24 to 36 hours as
the remnants of a westerly propagating shortwave trough along the
international border lifts north and becomes entrained in a broad
south-southwesterly flow pattern across the Great Basin. As it
does so, precipitable water anomalies of 150-200 percent of
normal will spread north across mainly Clark, Lincoln, and Mohave
Counties. This rich moisture will then be acted upon be favorable
jet dynamics and upslope orographics. Overall, this is a weather
pattern more typical of early fall transition events than your
standard monsoon set up, but may lead to some locally strong storm
development late tonight and into Saturday evening.

While the latest few iterations of the HRRR fail to develop much
nocturnal activity tonight, several members of the HREF suggest
convection developing late tonight across southern Mohave and
Clark Counties, and lifting north into Lincoln county prior to
daybreak. While the risk is conditional on storm development,
30-40 knots of deep layer southerly shear would be conducive to
some stronger updrafts capable of small hail and strong outflow
wind gusts. Tend to believe the HRRR is underdone with overnight
development, especially given the magnitude of Integrated Water
Vapor Transport suggested by forecast guidance. Whatever does
develop tonight, will tend to shift into Utah in the morning
hours, though continued moist southerly flow will foster
additional storm development during the afternoon, mainly across
northern Mohave County. With a favorable unidirectional southerly
flow pattern which would favor storm training, and HREF signal
for excessive precip, went ahead and issued a Flash Flood Watch
for northern Mohave County from 12z Saturday morning through 4z
tomorrow evening. Afternoon storm development further west
tomorrow closer to Las Vegas is uncertain, and may struggle due to
post- short wave subsidence, but a few isolated storms may still
develop with locally strong wind gusts and heavy rainfall
possible.

Further west across the Western Mojave Desert and Western edges of
the Great Basin, dry and breezy conditions can be expected both
Saturday and Sunday, with elevated fire danger the primary
concern. A Red Flag Warning remains in effect for Saturday and
Sunday in Esmeralda and Nye counties where fuels and conditions
are at critical risk. Meanwhile, temperatures areawide will remain
above normal, though clouds and precipitation may keep things
fairly close to normal across northern Mohave County Saturday.

Storm chances will persist across our eastern zones into Sunday,
though storm coverage is not expected to be quite as widespread as
on Saturday. Nonetheless, locally heavy rainfall and gusty winds
will remain possible with the stronger storms that do form.

.LONG TERM...Monday through Friday.

Overall weather pattern will change little next week, with dry and
breezy conditions persisting across our western zones and more
moist, convective conditions across our eastern zones. Where
exactly that boundary lies each day is less certain, though NBM
pops do shift noticeably eastward into mainly just northwest
Arizona Monday and Tuesday in response to the flow aloft shifting
more southwesterly. By midweek onward, flow backs to more
southerly again, opening the for for a westward creep of the
monsoonal moisture. Otherwise, temperatures will remain above
normal through the period.

&&

.AVIATION...For Harry Reid...Breezy south to southwest winds will
continue through the afternoon with over a 50% chance for gusts over
20KT through this evening. Winds will diminish tonight with gusts
ending after 03Z then southwest winds around 8KT overnight through
Saturday morning. Southeast winds around 150 degrees will set up
after 15Z Saturday then another round of breezy south to southwest
winds are expected Saturday afternoon. Winds saturday will be
stronger than today with as high probability (80%) for gusts over
20KT and a low probability (20%) for gusts over 25KT.

Most likely, it will be dry through the TAF period with no
thunderstorm impacts at the terminals. There is a low chance for
scattered precipitation to blossom after 09Z tonight through
southern Nevada through early Saturday morning, then another low
chance for thunderstorms to develop Saturday afternoon. Confidence
is currently too low to add convection to the TAFs however will need
to watch how things unfold. If convection does develop late tonight
and/or Saturday afternoon, lightning, sudden gusty winds, and CIGs
10kft are possible.

For the rest of southern Nevada, northwest Arizona and southeast
California...South to southwest winds with gusts of 20-25KT will
continue through the evening. Winds will diminish tonight with
diurnal wind trends expected through Saturday morning. Breezy south
to southwest winds will develop again Saturday with gusts 20-30KT
expected Saturday afternoon in many locations. There is a low chance
(20%-30%) for showers and thunderstorms to develop across Clark and
Lincoln Counties that would push north into central Nevada through
Saturday morning, then another round of convection may develop
Saturday afternoon in northern Mohave County through southwest Utah
and eastern Lincoln. Any thunderstorms that develop would bring the
risk of sudden gusty winds, lightning, heavy rain, and CIGs to 8kft-
10kft.

&&

.FIRE WEATHER...Dry and breezy conditions remain expected across
our western forecast area, namely across Nye and Esmeralda
Counties where a Red Flag Warning is in effect over the weekend.
Elevated fire danger will exist in Inyo County as well, though
fuels are not as critical. Points east across the Eastern Mojave
Desert, Lincoln County, and Northwest Arizona will see increasing
RH today and tonight as a weather disturbance moves through with
chances for rain and thunderstorm activity. Similar conditions
will continue into next week with dry and breezy conditions
persisting across our western forecast area.

&&

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

&&

$$

UPDATE...Woods
DISCUSSION...Outler
AVIATION...Nickerson

For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter