073
FXUS65 KVEF 181144
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
445 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. 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 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 12Z Forecast Package...
VFR conditions and daily wind pattern expected at KLAS for the next
24-36 hours. Light southerly winds early this morning become light
and variable in the mid morning hours. Hi-res guidance is hinting at
an earlier wind shift to the S around 18z, becoming SSW around 20z
with sporadic gusts to 20 kts into the evening. Gusts drop off after
sunset, then light southerly winds prevail into the overnight hours
tonight. No cig or vis concerns. Temperatures climb above 100
degrees between 18Z and 03Z.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 12Z Forecast Package...Elevated westerly winds
persist at KDAG through the night, decreasing after sunrise before
returning after 00z this evening. Elsewhere, daily wind patterns
expected at the rest of the terminals with light and variable winds
early this morning, becoming southerly and increasing to 08-12 kts
after 18z with sporadic gusts up to 20 kts. FEW to SCT clouds
between 15 and 25 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...Moore

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