010
FXUS65 KVEF 151748
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1048 AM PDT Sun Sep 15 2024

.SYNOPSIS...A large low pressure system dropping down from the
northwest into California and Nevada will bring widespread gusty
south to southwest winds to the region today through Monday along
with a significant cooling trend. A second trough of low pressure
will move across the area midweek bringing a reinforcing shot of
cool air along with scattered showers.
&&

.UPDATE...While not impactful, a bit of surprising weather going on
in eastern Lincoln County and southwest Utah this morning.
Mesoanalysis shows a pocket of higher moisture over that area with
PWATs at 0.75-1.00 and dewpoints in the upper 40s to lower 50s. This
has allowed for some surface instability to develop- the RAP
analysis shows 1000-1500J/Kg over Lincoln County now. With a weak
upper level wave moving into Utah, scattered cloud cover with few
showers and even isolated thunderstorms were able to develop through
the morning. Again- not impactful just interesting as models did not
have show this development. Everywhere else, it remained mostly
sunny.

For the rest of today- investigated this area of moisture and
considered if there would be afternoon precipitation associated with
it. However, the piece of energy that was able to kick off the stuff
this morning will continue to push east so forcing will wane. In
addition, drier air will move in behind it. This should prevent
showers from developing with peak heating as moisture and
instability diminish this afternoon. The NAM4km has at least a hint
of showers this morning, but even that model has any showers ending
and nothing developing in Lincoln County this afternoon. So, it will
be dry today. The main concern for today will be increasing south to
southwest winds as a potent upper level low digs into the region. No
changes to the overall expectations for today from the previous
forecast- expecting widespread gusts of 30-35 MPH through the
afternoon before strong winds move in this evening. No changes to
the wind headlines as impacts from winds through the afternoon will
be focused on the lakes region where a Lake Wind Advisory is in
effect. Choppy waves and gusty south winds will create hazardous
conditions on the lakes, boaters should be prepared or change plans
accordingly. Wind advisories dont go into effect until this evening
when probabilities for impactful wind gusts increase to over 50%.
Today`s highs will remain around normal and will be comparable to
yesterday.

-Nickerson-
&&

.PREVIOUS DISCUSSION...227 AM PDT Sun Sep 15 2024
.SHORT TERM...Today through Monday night.

Widespread south-southwest winds gusting 35 to 45 mph will be the
main weather concern across most of our forecast area later today
through Monday as a large closed low digs from the Pacific Northwest
into central California tonight then moves over Nevada Monday and
Monday night. Gusts 30 to 35 mph will be common across the region
this afternoon then a belt of gusts over 40 mph will likely develop
across the western Mojave Desert, Death Valley and Nye County this
evening and persist overnight and Monday. Wind Advisories are in
effect for these zones from 7 PM PDT this evening until 8 PM Monday
evening.

The HREF and NBM indicate occasional gusts over 40 mph will likely
spread across much of northeast San Bernardino, Clark, Lincoln and
Mohave counties Monday morning through early Monday evening. Wind
Advisories are in effect for these zones from 10 AM PDT Monday
morning through 8 PM Monday evening. The slow moving nature of the
system should make this a fairly low-impact event, but it is the
first widespread gradient wind event with gusts over 40 mph of the
fall season. This will usher in a 10-15 degree cooling trend with
temperatures falling into the lower 80s in Las Vegas on Monday and
lows dipping to 55-60 degrees in the Las Vegas Valley Monday night.

A secondary concern is that limited moisture with the system near
the cold pool could also result in a dusting of snow in the Sierra
and White Mountains above 9,000 feet Monday and Monday night.
Scattered light showers and an isolated thunderstorm will also be
possible across northern Inyo, Esmeralda and central Nye counties
Monday.

The latest HREF indicates that moisture that had worked its way up
the lower Colorado River Valley and southern Mohave County will be
too shallow and will be swept east of Mohave County today before
convection has a chance to develop so the chance of showers or
thunderstorms has diminished below 10 percent for that area.

.LONG TERM...Tuesday through Saturday

Lighter winds are expected by Tuesday as the tight pressure gradient
and low level jet moves east along with the trough. However, the
system will leave cold air over the region in its wake. Morning lows
on Tuesday will be 10 to 15 degrees below normal for mid September.
Another deep low will drop down from the Pacific Northwest into the
Great Basin midweek. It should provide some reenforcement for cool
temperatures, keeping highs around 10 degrees below normal through
the end of the workweek. Some guidance is not showing a strong wind
signal with this system, but others highlight the potential for
elevated winds. This will depend on the placement of the trough and
where the tightest pressure gradient will form. Lastly, moisture
advection with the system will bring increased precipitation chances
midweek, particularly in the southern Great Basin. As this system
exits towards the end of the week, Pacific high pressure moves in
behind it and should boost temperatures for next weekend.

&&

.AVIATION...For Harry Reid...Gusty winds will return to the Las
Vegas Valley late this morning into early this afternoon. Wind
direction will vary from 160 to 200 through the afternoon with gust
speeds between 20 and 30 kts (20 percent chance of exceeding 30
kts). Wind direction will become west-southwesterly after sunset
with a high probability (over 70%) of occasional gusts continuing
overnight. Monday will be characterized by gusty southwest winds
through the entire day. No operationally significant cloud cover
through the TAF period.

For the rest of southern Nevada, southeastern California, and
northwestern Arizona...Gusty south winds will pick up across the
region this afternoon with gust speeds between 20 and 30 kts. The
exception is KDAG, which will prevail from the west. Gust speed and
frequency will diminish after sunset, but occasional gusts to 20 kts
should be expected through the overnight period. Hazy skies may
reduce slantwise visibilities in the Daggett and Beatty corridors
from ongoing southern California wildfires. No operationally
significant cloud cover expected through the TAF period with the
exception of KBIH with SCT-BKN aoa 10kft increasing through the day.
&&


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

&&

$$

SHORT TERM...Adair
LONG TERM...Meltzer
AVIATION...Soulat

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