874
FXUS65 KVEF 181701
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1001 AM PDT Mon Aug 18 2025

.KEY MESSAGES...

* Temperatures warm through the week starting today. Increasing
  confidence for dangerous heat Wednesday through at least Saturday
  with above normal high temperatures and minimal overnight relief
  as low temperatures remain very warm.

* Moisture increase mid week with anomalous moisture over the region
  through the weekend. Precipitation chances increases through the
  week, with the highest risk for thunderstorm impacts being over
  the terrain this the weekend.

* Very dry conditions with dry low levels could result in lightning
  strikes starting wildfires.

&&

.DISCUSSION...Today through Sunday.

A warming trend is expected starting today as high pressure builds
over the Four Corners region. Above normal temperatures return
Tuesday and will continue to climb to 5-7 degrees above normal
Thursday and Friday. While high temperatures will not be the most
extreme we have seen this summer, overnight temperatures will play a
role in the heat impacts as moisture could keep lows very warm. NBM
shows a 30% chance that Las Vegas, NV will not fall below 90F
Thursday night through Saturday night. Given the duration of the
heat, the above normal daytime temperatures, and the minimal
overnight relief- this yields widespread Major HeatRisk with even
some pockets in the Extreme category. Increasing moisture does
introduce some uncertainty in the temperature forecast, however NBm
shows minimal spread in high temperatures. Given all this- there is
enough confidence at this time to issue a Heat Watch for much of the
region for Wednesday through Saturday. While temperatures will begin
to cool Saturday, lows in the morning will still be warm and Heat
Risk still shows some pockets of Major Heat Risk. Can adjust timing
and areas as needed when/if the Watch is converted to a
Warning/Advisory if the temperature forecast changes.

As the area of high pressure sets up over the Four Corners, the flow
will turn south to southeast which will advect moisture into the
region. Moisture increases will start Tuesday and continue through
much of the week, however showers and thunderstorms may struggle at
first as upper level height rises could create a mid-level
subsidence inversion (which is noted on GFS forecast soundings).
This inversion slowly erodes each day starting Thursday with
precipitation chances spreading eastward as subsidence aloft wanes.
Synoptic forcing will be lacking, so daily changes in the patterns
and mesoscale features could drive convection (outside of terrain
driven development). The highest and most widespread precipitation
chances are this weekend as 150%-175% of normal PWATs set up over
the region. The finer convective details remain to be seen at this
range, all the typical monsoon hazards (flash flooding, strong
outflow winds, frequent lightning) could be in play.

Wildfires will also be a concern with convection, especially earlier
in the period. It has been a very dry summer, and brush and trees
are extremely dry. Any thunderstorm could ignite a fire via a
lightning strike outside the main rain shaft. At this time, it looks
like storms will start off as a mix of wet and dry, transitioning to
more wet fairly quickly, so the coverage of dry lightning will
likely be too low to justify Red Flag Warnings. That said, new fire
ignitions will be a concern until there has been wetting rain.
&&


.AVIATION...For Harry Reid...For the 18Z Forecast Package...Wind
directions will follow typical diurnal patterns today, with east-
southeasterly winds this afternoon between 7 and 10 kts, becoming
southwesterly after sunset. FEW aoa 12 kft expected overnight
through the remainder of the TAF period. Temperatures will be at or
above 100 degrees from 20 to 03Z, peaking around 103.

For the rest of southern Nevada, northwestern Arizona and
southeastern California...For the 18Z Forecast Package...Wind speeds
and directions will follow typical diurnal patterns today, with
speeds between 6 and 10 kts. The exception will be KBIH, where south-
southeasterly wind gusts will peak between 25 and 30 kts before
dropping off after sunset. FEW aoa 12 kft across southern Nevada
overnight through the remainder of the TAF period.
&&


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

&&

$$

DISCUSSION...Nickerson
AVIATION...Soulat

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