508
FXUS65 KVEF 190807
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
105 AM PDT Wed Aug 19 2026

.KEY MESSAGES...

* Temperatures peak on midweek 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 Early Next Week.

Another stretch of above normal temperatures continues this week for
the Desert Southwest as strong ridging builds in overhead. Currently
a 597dm high is centered directly over the Colorado River Valley and
Las Vegas , 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. Tuesday hit a high of 109F in Las Vegas and with Wednesday
and Thursday likely being the hottest days this week, there`s a good
chance the valley may reach 110F the next few days.  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. There are several
climate sites that are currently tied or broke a record warm low
temperatures for Tuesday, which may hold since temperatures have
been slow to cool off earlier this evening. 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 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 supporting an increase in shower and
thunderstorm coverage. 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 levels. There is still significant uncertainty in
potential tropical developments off the Coast of Mexico and its
influence on weather here locally and the west coast. The ECMWF and
its ensembles have been consistent in showing tropical moisture
spreading northward by the middle of next week impacting portions of
California and Nevada. However the GFS and its ensembles are showing
a weaker signal for this occurrence. High confidence exists in a
pattern favorable for monsoon storms Friday through Sunday and some
level of increased moisture persisting into next week but confidence
is only marginal next week in how much moisture will be around and
how widespread storm coverage could be.


&&

.AVIATION...For Harry Reid...For the 06Z Forecast Package...
Southwesterly winds will become lighter and variable overnight
before settling from the southeast late Wednesday morning. Winds
will gradually veer to the southwest throughout the afternoon, with
15 to 25 expected through sunset. Wind gusts will drop off after
sunset, with winds continuing to maintain a southwesterly direction
through the overnight hours. VFR conditions prevail with FEW-SCT
clouds with bases between 10-25kft. Temperatures will exceed 100
degrees between 18Z and 04Z.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 06Z Forecast Package...Winds will remain
light, 10 knots or less, overnight and will follow typical diurnal
directional trends through Wednesday morning. Breezy
southerly winds will pick up across the region late morning/early
afternoon on Wednesday, with 15 to 25 knot gusts expected through
sunset. The exception is the western Mojave Desert, including
KDAG, where winds elevated westerly winds will continue through
late Wednesday morning when winds will become light and variable.
VFR conditions otherwise prevail, with passing bands of clouds
with bases at or above 10kft.

&&

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

&&

$$

DISCUSSION...Moore
AVIATION...Stessman

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

NWS Las Vegas (VEF) Office