Flash Flooding and High Wind in California, November 7 to 8, 2022

Area Forecast Discussion
National Weather Service Las Vegas NV
259 AM PST Mon Nov 7 2022

.SYNOPSIS...An approaching Pacific storm will result in
deteriorating weather across the area especially Tuesday through
early Wednesday. Snow will begin across the Sierra this morning and
spread across the higher elevations of southern Nevada by Tuesday.
The Mojave Desert region and lower elevations will see widespread
rain and periods of strong winds with temperatures decreasing 10 to
15 degrees. Dry weather will return Thursday through the weekend.
&&

.SHORT TERM...Today through Tuesday night.

The large low pressure system looked impressive on satellite loops
with a broad area of cold air circulating over the Pacific Northwest
with a moisture plume (atmospheric river) rounding the base of the
system into central California. The latest ensemble-based indicators
continue to support the messaging that this will be a major storm
for the Sierra and will bring beneficial precipitation to most of the
western states especially Tuesday into Wednesday. It will also bring
widespread strong winds, especially Tuesday afternoon and Tuesday
night as the system moves inland.

The limiting factor for snow in all but the highest mountains will
be the relatively warm air accompanying the main moisture plume.
Snow levels across southern Nevada and northwest Arizona should
remain above 8000 feet through Tuesday afternoon then will lower
Tuesday night as the large cold pool moves inland but precipitation
begins to taper with the concentrated moisture moving away to the
east. The Spring Mountains could see a period of heavy precipitation
late Tuesday evening and overnight as snow levels lower to between
6000 and 7000 feet which will favor heavy snow above 8000 feet and
significant accumulation down to around 7000 feet. Meanwhile the
deserts and lower valleys should easily see widespread rain amounts
of 0.25"-0.75" with some areas over 1". Rainfall intensity should be
generally light to moderate which will mitigate flooding concerns,
but minor impacts from runoff can be expected.

.LONG TERM...Wednesday through Sunday.

Unsettled, cold conditions will persist into Wednesday as incoming
potent trough slowly shifts east across the Great Basin. Due to its
slower movement, AR will likely still be across parts of San
Bernardino, Clark and Mohave Counties in the morning before it
shifts primarily over Mohave County during the afternoon. Periods of
moderate rain accompanied by thunderstorms will be possible leading
to the threat of minor flooding of low lying areas. Still some
uncertainty in snow amounts across the Great Basin and northwest
Arizona as the prolonged period of higher snow levels ahead of the
system will probably lead to more rain than snow. Snow levels will
stay elevated above 7500 feet in Mohave County through the morning
before falling to around 6000 feet by late afternoon. For San
Bernardino, Clark and Lincoln Counties the snow level will be around
6500-7000 feet before falling to 5000-5500 feet in the afternoon.
Further west, snow levels will be hovering around 4000 feet in the
Owens Valley. High temperatures will be some 10-20 degrees below
normal.

Light precipitation will continue into Wednesday evening before
finally exiting Mohave County after midnight.

Some uncertainty exists in the Thursday-Sunday timeframe. WPC
cluster analysis indicates the region will remain generally under a
zonal to potential weak ridge. However, there are several ensemble
members suggesting a weak shortwave breaking through and moving
through the northern Great Basin this weekend. Could see some light
showers in far northwest Inyo County, while the remainder of the
region looks dry. Temperatures will stay cool with highs some 6-12
degrees below normal. Also, probably get some stronger north wind
gusts localized to the lower CRV behind the exiting trough Thursday
and Friday.
&&

.AVIATION...For Harry Reid...South winds gusting to around 20 knots
are expected through about 8 am before increasing out of the
southwest mid morning with gusts 30-35 knots. No significant cloud
cover is expected until Tuesday morning when ceilings around 10k
feet are expected. Strong southwest winds with gusts 35-40 knots are
forecast for Tuesday with CIGs dropping below 5k feet in rain
Tuesday afternoon.

For the rest of southern Nevada, northwest Arizona and southeast
California...South to southwest winds will increase this morning and
continue through the afternoon with gusts 30-35 knots at the Las
Vegas Valley TAF sites and 25-30 knots at KBIH, KDAG, KEED, and
KIFP. Some decrease in wind is expected tonight before increasing
again on Tuesday with gusts 30-40 knots possible. Expect rain along
with lower ceilings and mountain obscurations beginning this evening
in KBIH with rain spreading to KDAG and the Las Vegas Valley TAF
sites later tonight and then across the Colorado River Valley TAF
sites late Tuesday morning.
&&

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

SHORT TERM...Adair
LONG TERM...Pierce
AVIATION...Salmen

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