834
FXUS65 KVEF 180744
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1245 AM PDT Tue Aug 18 2026

.KEY MESSAGES...

* Temperatures peak on Wednesday and Thursday, with above- normal
  afternoon highs and near-record morning lows.

* Monsoon moisture increases late this week into the weekend,
  accompanied by increased shower and thunderstorm chances.

&&

.DISCUSSION...Through next weekend.

Another stretch of above normal temperatures in the forecast this
week for the Desert Southwest as strong ridging builds in overhead.
Currently a 597dm high is centered over Southwest Arizona, slowly
shifting north and eastward through the week into the four corners
region. Strong subsidence under the ridge in combination with above
normal heights and 850mb temperatures for this time of year will
lead to a period of dangerous temperatures and widespread Major Heat
Risk in Desert Valleys. In general, expect highs to be around 5-10
degrees above normal for Mid August with the Colorado River Valley
having the best chance at exceeding 110F for highs. Max temps may
near 110F in the Las Vegas Valley Wednesday and Thursday this week.
Leftover monsoonal moisture, particularly in the southern portion of
the forecast area, Southern NV, Mohave County AZ, and the Colorado
River Valley, will also lead to near record warm overnight lows this
week in the 80s and 90s, further exacerbating the dangerous heat as
little to no heat relief will occur at night. The Extreme Heat
Warning remains in effect for portions of southern Nevada,
southeastern California, and northwestern Arizona Tuesday morning
through Friday evening. By the weekend, upper heights still remain
above average, however with the approaching trough and increase in
monsoon moisture and clouds, expect highs several degrees "cooler"
than what is observed middle of this week.

By Thursday, the upper ridge overhead shifts into the Four Corners
region while a trough approaches the west coast. Low and mid level
flow becomes southerly once again, advecting in monsoonal back
northward northward through the Colorado River Valley and into
Southern Nevada. Precipitable Water values near and exceed one inch
on Thursday as moisture spread northward, then approach 1.20-1.30"
end of the week and Saturday. Expect only isolated thunderstorm
activity Thursday as guidance hints at only marginal instability to
support convective development. Main threat area is likely in Mohave
County AZ and potentially some higher terrain in Southern NV.
Scattered to numerous convection expected Friday into the weekend
each afternoon and evening with the greatest threat again in Mohave
County and higher terrain of Southern Nevada as both moisture
content and instability will be more favorable for storms. Any storm
will have the capability of producing locally heavy rain, gusty
winds, lightning, and a flood threat. Long range guidance continues
to signal that monsoon moisture remains in the region going into
next week but with varying degrees of moisture as there is
significant uncertainty in potential tropical developments off the
Coast of Mexico and its influence on weather here locally. High
confidence exists in a pattern favorable for monsoon storms Friday
through Sunday, but confidence starts to drop off going into next
week regarding storm chances and coverage.


&&

.AVIATION...For Harry Reid...For the 06Z Forecast
Package...Southwesterly winds of less than 10 knots become
variable by tomorrow morning. Southerly to southwesterly winds
return tomorrow afternoon, with occasional gusts between 15 and 20
knots, decreasing after sunset. Temperatures climb above 100
degrees between 18Z and 04Z.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 06Z Forecast Package...Elevated westerly winds
persist at KDAG through the night, decreasing tomorrow before
returning tomorrow evening. Winds increase out of the south to
southwest in the Las Vegas Valley, Colorado River Valley, and Owens
Valley during the afternoon. FEW to SCT clouds between 10 and 20 kft
AGL continue through the TAF period.

&&

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

&&

$$

DISCUSSION...Moore
AVIATION...Meltzer

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