Flash Flood Warning 3, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
621 AM PDT Wed Mar 15 2023

.SYNOPSIS...An atmospheric river event will bring widespread rain
and high elevation snow along with areas of strong winds to the
southwest states through this morning. Nature of the storms becomes
convective this afternoon and evening with thunderstorms producing
hail, gusty winds and heavy rain. Dry weather will follow the rest
of the week but additional Pacific moisture will provide chances for
unsettled weather late in the weekend.
&&

.UPDATE...In collaboration with Elko and Salt Lake City the wind
advisory has been cancelled.

&&

.SHORT TERM...Through Thursday night.

In the past 6 hours, observations show another 0.50"-0.75" of rain
has fallen below 7000 feet in the the Owens Valley. So far, only
seeing slight rises on creeks that LADWP has instrumentation on.
Mostly a 0.25" or less elsewhere.

Models in good agreement shifting a trough across the region today
and tonight. Hi-res simulations support the idea of a broad swath of
precipitation developing across southeast California, southeast
Nevada and Mohave County in the next few hours. This area expected
to exit Mohave County late morning. Nature of precipitation then
quickly turns convective this afternoon and evening. HREF MUCAPE of
500-750 J/KG progged within the lower CRV and Mohave County late
this afternoon and evening. Not sure if these values can be realized
due to the morning rains but potential exists. HRRR indicates
Lincoln, Clark, far eastern San Bernardino and Mohave Counties have
the best chance for thunderstorms. Hail, gusty wind and heavy rain
will accompany those thunderstorms.

As the trough shifts further east into Arizona, thunderstorms will
exit Mohave County late this evening with a few showers potentially
lingering into early Thursday morning. Much quieter Thursday, with
only a slight chance of a shower building over far eastern Mohave
County in the afternoon.

Excessive Rain Outlook issued by WPC placed parts of Lincoln, NE
Clark and Mohave Counties under Marginal to Slight Risk through 12z
Thursday. Due to antecedent conditions and since stream flows have
been running above normal due to recent rain/snowmelt will be
issuing a Flood Watch through Thursday afternoon and additional
rises likely.

.LONG TERM....Friday through Tuesday.

A more zonal pattern sets up as we head into the weekend. During
this time, ensemble guidance depicts several subtle shortwaves
passing through, with anomalous moisture (up to 150% of normal) in
tow. This may be enough to produce light precipitation, mostly tied
to upslope flow given the marginal forcing. The latest NBM give the
area less than a 20% chance of precipitation Friday night as the
first wave moves through. PoPs increase again Sunday afternoon, with
the NBM giving Lincoln and Mohave Counties, as well as the Sierra
and Spring Mountains, a 30-60% of precipitation. Snow levels for
both these possible events are forecast to be between 5500-6500'.
Other than the precipitation chances, the weekend looks rather
pleasant with temperatures a few degrees below normal and light
winds.

Early next week, PoPs become more widespread as another potential
atmospheric river looms in the Pacific. The exact timing, location,
and trajectory of this AR is still uncertain, as the GEFS favors
landfall in central/southern California while landfall in the Euro
ensemble is along the US-Mexico border. Despite details being rather
fuzzy, confidence is quite high in cool and wet conditions
continuing through next week. The CPC 6-10 day outlook gives our CWA
a 70+% probability of above-normal precipitation. It's the winter
that just won't quit.
&&

.AVIATION...For Harry Reid...Periods of rain through the
morning will drop ceilings as low as 3000-4000 feet. Rain chances at
the terminal will decrease around 16Z, with the best chances
shifting to areas southeast of I-15 in the Peach Springs and Mormon
Mesa corridors through late morning. During the day, scattered
showers and isolated thunderstorms are expected to develop, with the
greatest chances over the mountains, and a lower chance at the
terminal. Any storm near the terminal could drop ceilings to 3000 to
4000 feet. South to southwest winds are expected through Wednesday,
occasionally gusting as high as 25 knots, before shifting to the
northwest Wednesday night. Northerly winds gusting 15 to 20 knots
are expected Thursday, with quiet weather likely on Friday.

For the rest of southern Nevada, northwest Arizona and southeast
California...Rain and high elevation snow will continue over nearly
the entire region this morning, with ceilings below 3000 feet and
terrain obscuration common. This afternoon and evening, widespread
showers and scattered thunderstorms are expected, primarily southeast
of a line from Rachel to Death Valley to Barstow. The main threats
with thunderstorms will be erratic, gusty winds, hail and low
ceilings with terrain obscuration. Dry weather and breezy northerly
winds are expected Thursday, with the strongest gusts of around 30
knots in the Colorado River Valley. Quieter weather is expected
Friday.
&&

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

SHORT TERM/AVIATION...Pierce
LONG TERM...Woods

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