263
FXUS65 KVEF 172143
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
243 PM PDT Sun Aug 17 2025

.KEY MESSAGES...

* Dry conditions prevail through Monday with temperatures near or
  slightly below normal.

* Temperatures and precipitation chances increase mid to late week
  as a more traditional monsoon pattern sets up.

* Heat could reach dangerous levels as early as Wednesday, but
  clouds and thunderstorms could also keep the heat down. It has
  been hot and dry for a long time, so lightning strikes could start
  wildfires.
&&

.DISCUSSION...through Saturday. Midday satellite loop showed a few
shallow cumulus developing over the Sierra Nevada and the higher
terrain of the southern Great Basin, with clear skies elsewhere.
Surface obs showed breezy south to southwest winds, temperatures
slightly warmer and dewpoints lower than 24 hours ago. Very little
change to the overall forecast reasoning. Dry south to southwest
flow will remain in place for one more day before shifting to more
southeasterly in response to high pressure over the southern Plains
repositioning over the Four Corners. This is our typical summer
monsoon setup and will bring a significant change, although there
are a lot of details still uncertain. Humidity will be ramping up
during the middle of the week, but thunderstorm chances are less
certain. The NBM shows chances beginning in Mohave County Wednesday
and pushing westward Thursday through Saturday, which is a good
starting point, but should not be seen as the final word. As the
high builds westward, temperatures in our region will rise above
normal for late August. The heat will be favorable for triggering at
least isolated storms, especially over the mountains, but the
proximity of the high will result in warm mid-level temps also,
which could put a lid on more widespread thunderstorms. There is no
clear forcing mechanism in the models yet, but mesoscale convective
vortices, outflow boundaries, and the like cannot be well-forecast
more than a day or so ahead of time (and often less!). Time will
tell. The heat will also be its own story. If widespread cloud cover
and/or thunderstorms aren`t present, the heat could reach dangerous
levels possibly as early as Wednesday. Extreme Heat Watches will
likely be needed tomorrow. Wildfires will also be a concern. 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 00Z Forecast Package...Winds
will gust 15 to 20 knots from the south through the afternoon, then
settle down after sunset. On Monday, winds could be more easterly
from late morning through early afternoon, with an outside chance of
an occasional gust over 10 knots, before shifting to southerly. VFR
conditions expected both days. Temperatures above 100F through 01Z
this afternoon, then again Monday from about 21Z to 02Z, with a high
around 103F.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 00Z Forecast Package...Generally southerly
winds gusting 15 to 25 knots expected through Monday, with the usual
exceptions in areas such as KDAG where terrain causes winds to blow
from a different direction. VFR conditions expected both days.
&&

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

$$

DISCUSSION...Morgan
AVIATION...Morgan

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