Severe Thunderstorm Warning 20, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
150 PM PDT Tue Aug 6 2024

.SYNOPSIS...Excessive Heat will continue through this evening
with marginal risk of severe thunderstorms in southern Mohave County
and the lower Colorado River Valley late this afternoon and evening.
A modest increase in monsoonal moisture Wednesday and beyond will
result in moderating temperatures, through still above normal, along
with thunderstorm activity spreading into the eastern Mojave Desert
through the weekend.

&&

.SHORT TERM...Through Wednesday night.

Another hot day across the region as high pressure remains the
dominant weather feature over the Desert Southwest. Excessive heat
warnings remain in effect until 9pm this evening with several
locations at or near record highs once again. Although high pressure
will remain in place Wednesday and even shift slightly further west
in response to an inverted trough moving westward across northern
Mexico, it does begin to weaken. This slight weakening of the high
combined with increasing monsoonal moisture should allow
temperatures to drop a few degrees Wednesday keeping us below the
excessive heat criteria.

For the remainder of this afternoon and evening, we will see
thunderstorms firing once again over portions of Mohave County. Most
of the thunderstorm activity will remain pulsy, but with greater
dynamics and shear over far southern Mohave and northern La Paz
Counties, these could become more organized. The greatest threat
from convection this evening will be strong outflow winds. Several
hires models have remained consistent through the morning and early
afternoon showing a strong outflow boundary pushing west and
northwest across the lower Colorado River Valley between 7pm and
10pm. Wind up to 50 mph will be possible as it pushes through the
lower CRV. Eventually these winds make it to southern Nevada and
even into the Las Vegas Valley, but they are expected to be much
weaker by they time they reach this far north.

That southeasterly outflow wind will bring an increase in moisture
further west/northwest into the Mojave Desert and southeast Nevada
Wednesday for an uptick in thunderstorm chances. Could see a repeat
of storms moving into Mohave County off the higher terrain of
central Arizona, albeit potentially with less wind potential and
transitioning to more of a flash flood threat.

.LONG TERM...Thursday through Monday.

Not much change to forecast thinking today vs yesterday. Models
remain in very good agreement with each other and with previous
runs, so confidence is above average. The big hot ridge retains its
grip on our area, and by Thursday the easterly wave rotating around
its southern periphery should be over the northern Gulf of
California. This should help drag higher humidity and thunderstorm
chances a little farther west, reaching roughly the Interstate 15
corridor by Friday, then expanding farther west and north into
Lincoln, Nye, and far eastern Inyo counties over the weekend.
Meanwhile, temperatures come down a few degrees, remaining above
early August normals, but dropping just enough to keep HeatRisk out
of the Major and Extreme categories. Oppressively warm overnight
lows will continue in the lower elevations and urban areas, except
in areas which are affected by thunderstorms. There is still
agreement on a trough reaching the West Coast Monday, which could
start to knock temperatures and humidity down a little, especially
in areas northwest of Interstate 15. The big questions will be how
far south and east the effects of this trough might be felt, and for
how long.

&&

.AVIATION...For Harry Reid...Winds will gradually shift to the
southwest this afternoon with speeds of less than 10 knots.
Convection will begin this afternoon in northwest Arizona and
although the storms are not expected to reach the terminal,
southerly outflow winds may reach the terminal overnight. Gusts
between 15 and 20 knots are possible between 06Z and 12Z with
occasional lulls possible. Winds should decrease and become variable
later tomorrow morning. Southeasterly winds return tomorrow
afternoon with speeds of less than 10 knots.

For the rest of southern Nevada, northwest Arizona and southeast
California...The primary weather concern is gusty outflow winds this
evening and overnight originating from convection in Arizona. Peak
gusts of 30 knots will reach the Colorado River Valley terminals
between 03Z and 05Z. Lighter gusts between 15 and 20 knots will
reach the Las Vegas Valley terminals between 06 and 12Z. The
thunderstorms themselves are not expected to reach any terminal.
Besides the outflow, diurnal wind patterns are expected at these
locations as well as KDAG and KBIH.

&&

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

&&

SHORT TERM...Gorelow
LONG TERM...Morgan
AVIATION...Meltzer

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