Flash Flooding and Damaging Winds in California, August 21, 2024

Area Forecast Discussion
National Weather Service Las Vegas NV
221 PM PDT Wed Aug 21 2024

.SYNOPSIS...Two more days of monsoonal activity is expected across
northwestern Arizona before a trough of low pressure moves into
the intermountain-west and dries out the region. This trough will
also help to cool temperatures to below-average readings by this
weekend. Meanwhile, gusty southwest winds will pick up Thursday
and Friday afternoons, increasing the danger of fires across the
southern Great Basin. Unfortunately, the cool-down will be short,
and temperatures will rebound back to above-normal levels by early
next week.
&&

.SHORT TERM...Through Friday.

The combination of a ridge over Texas and a trough dropping into
the Pacific Northwest will work together to pull in moist air from
northwest Mexico and the Gulf of California. Dewpoints remain
close to 60 as far north as Laughlin this afternoon, and PWAT
values of 1.25 to 1.5 inches will continue to spread north tonight
and Thursday. Isolated thunderstorms are possible over central
and southern Mohave County this afternoon and evening, but a
better chance for storms will develop overnight and Thursday,
mainly over the northern half of Mohave County. Given the
increased moisture levels and favorable wind profile that would
favor the training of cells, a Flash Flood Watch has been issued
for the northern half of Mohave County from late this evening
through Thursday evening. Most of the area covered by the watch
will see around a half-inch of rain. Still, Isolated amounts of
1.5 to 2 inches will be possible, especially over the higher
terrain near Colorado City and Pipe Spring. The moisture will
begin to exit the region on Friday resulting in just a slight
chance of storms over far eastern areas.

The trough mentioned above will continue to move into the
intermountain-west by this weekend. Widespread south-to-southwest
winds gusting 30 to 40 mph are possible ahead of the trough
tomorrow and Friday over southeast California and southern Nevada.
These winds, along with the drier conditions further west, will
lead to an increased fire risk, mainly across southern Nevada, and
a Red Flag Warning has been issued for this area on Thursday and
Friday. Friday looks to be the day with the highest potential for
gusty winds, and headlines may be needed for that period. The good
part about the trough is that temperatures will cool off, with
readings falling to just below 100 in the Las Vegas Valley by
Friday.

.LONG TERM...Saturday through Tuesday.

Deep West Coast trough will begin to weaken and swing inland over
the weekend, ushering in dry and cooler air to the region. There
remains some discrepancy among forecast guidance on finer details of
the trough, namely how quickly it weakens and how fast it lifts into
the northern Rockies. But regardless, confidence is high that
temperatures will drop to their coolest levels since Mid-June. NBM
probabilities for a high temperature Saturday of 99 or less are
currently near 85 percent, with about a 25 percent chance of
being 95 degrees or less. Meanwhile, morning low temperatures in
parts of the Owens Valley near Bishop will bottom out in the lower
40s by Sunday morning. The taste of fall won't last long however
as ridging will begin to build back across the Southwest early
next week, helping to send temperatures back closer to normal by
Monday and Tuesday.
&&

.AVIATION...For Harry Reid...Breezy south-southwest winds throughout
the TAF period as wind direction stays between 160-240. Speeds
generally 10-15 knots with a 90% chance of gusts 20-30 knots during
the daytime hours. After 03z, the probability of sustained winds 10+
knots drops below 40% and remains there until 16z tomorrow. FEW-SCT
clouds at 10+ kft today, but any afternoon convection remains
confined to NW Arizona.

For the rest of southern Nevada, northwest Arizona and southeast
California...South-southwesterly breezes across the region today,
with more westerly winds at KDAG. Speeds this afternoon 10-15 knots
with gusts 20-30 knots. Winds at most sites will subside around
sunset. Clear skies at KBIH and KDAG, while sites farther east will
see FEW-SCT clouds around 10-15kft. Limited potential for convective
influence as storms are expected to remain in NW Arizona. KEED and
KIFP have the best chance of thunderstorm impacts (rain/wind) today
and tonight, but these chances remain below 20%.
&&

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

&&

SHORT TERM...Planz
LONG TERM...Outler
AVIATION...Woods

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