FXUS65 KVEF 250814
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
114 AM PDT Fri Oct 25 2024

.SYNOPSIS...Warm and dry conditions will continue through Sunday
under high pressure. A significant change in the weather pattern
arrives Monday as low pressure from the Gulf of Alaska brings
increased winds, cooler temperatures, and precipitation potential to
parts of the forecast area.
&&

.SHORT TERM...through Sunday night. Midnight satellite loop showed
scattered cirrus moving east over Mohave, Lincoln, Clark, and
eastern San Bernardino counties, with clear skies farther west.
Surface obs showed light winds and temperatures a few degrees lower
on average than 24 hours ago. Very little change in forecast
thinking. High pressure will remain in place through Saturday,
keeping dry weather and above normal temperatures in the forecast,
with periods of passing high clouds. Sunday and Sunday night will be
when things start to change. As noted yesterday, the leading
shortwave trough will be coming into the West Coast ahead of the
main low nearing Vancouver Island. This will increase surface
pressure gradients, upper level winds, and thermal gradients,
causing winds to pick up Sunday and especially Sunday night. Wind
Advisories may be needed for the Barstow area as early as Sunday
night. The increasing winds and deeper mixing will offset or even
outweigh falling heights, so temperatures will not fall from
Saturday to Sunday and may even rise a bit more. NBM 4.2 via the
WSUP 1-D viewer still gives a 50 percent chance for Las Vegas to
reach 90 degrees on Sunday.

.LONG TERM...Monday through next Friday.

Attention turns to a closed low as it approaches the western coast
of Canada through the weekend. By the start of the next work week,
the associated trough will have dug through the western CONUS, with
the trough axis pushing through the Mojave Desert on Monday.

We remain confident in the timing and placement of this system, as
well as the temperature drop that will correspond with the cold
frontal passage. Temperatures will drop 15 to 20 degrees between
Sunday and Wednesday, shifting the region from above-average
temperatures to below-average temperatures for the remainder of the
forecast period.

Along with a stark drop in temperatures, we can expect gusty pre-
frontal southwesterly winds on Monday. As mentioned in the previous
forecast discussion, the NBM continues to highlight a band of 75-95%
chance of gusts exceeding 40 mph from western San Bernardino County
through Las Vegas into northern Mohave County / the Arizona Strip on
Monday. Post-frontal northwesterly winds will take over across the
region through the day on Tuesday, but are not forecast to be as
strong as the pre-frontal winds with this event. This is likely due
to the fact that the trough will have a more eastward trajectory
(rather than a south-southeastward trajectory) than last week's wind
event, creating less favorable upper-level pressure gradient
directions.

Finally, precipitation chances will increase with this system. As
mentioned previously, this remains the least confident part of the
forecast, as the moisture increase does not temporally line up well
with the needed dynamics. However, the mountains and other areas of
higher terrain can expect increased precipitation chances due to
assistance from orographic lift. Due to snow levels dropping between
5000 and 5500 feet Monday evening, higher elevations of Lincoln
County can expect a dusting of snow.

Wednesday onward, an active fall-like weather pattern continues,
though details are unclear at this time.
&&

.AVIATION...For Harry Reid...Wind speeds of 8 knots or less will
continue again today and favor an easterly direction from late this
morning through the afternoon and a westerly direction this evening
into Saturday morning.  VFR conditions will prevail through the TAF
period with clear skies through the afternoon followed by FEW to SCT
high clouds with bases AOA 15kft moving across the valley overnight
and Saturday.

For the rest of southern Nevada, northwest Arizona and southeast
California...Winds will remain less than 10 knots and favor typical
diurnal directions today into Saturday.  VFR conditions are expected
at all regional TAF sites, although a FEW to SCT high clouds with
bases AOA 15kft will move across the area west to east beginning
late this afternoon and continue into Saturday morning.
&&

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

$$

SHORT TERM...Morgan
LONG TERM...Soulat
AVIATION...Planz

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