-- Discussion containing changed information from previous version are highlighted. --
297
FXUS65 KVEF 201701
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1000 AM PDT Thu Jun 20 2024

.SYNOPSIS...Increasing temperatures and the first influx of
moisture associated with the North American Monsoon are expected
in the coming days. Temperatures will climb to around 6-8 degrees
above normal over the weekend while tropical moisture will
increase over western Arizona, southern Nevada and eastern
California Friday through early next week. This moisture will
lead to an increase in shower and thunderstorm chances, while the
hottest temperatures have shifted to next week when decreasing
moisture is forecast.

&&

.UPDATE...
-- Changed Discussion --
The current forecast remains on track with no major
changes necessary at this time. Temperatures will continue to warm
over the next few days as we head into the weekend. Remnant moisture
from Tropical Depression Alberto will be advected into the southern
and eastern portions of our forecast area beginning as early as
Friday in eastern Mohave County. The best chances for weekend
showers and thunderstorms will be south and east of the I-15
corridor. Even with the anomalous moisture and increasing
precipitation chances, confidence regarding exact precipitation
amounts remains low due to uncertainty regarding where showers and
thunderstorms will develop. Additionally, there is a chance that
cloud cover associated with this moisture surge will limit daytime
heating, therefore limiting afternoon convection.
-- End Changed Discussion --

&&

.DISCUSSION...
-- Changed Discussion --
Through next Wednesday.

There are few concerns over the next day or two with generally
clear skies, warming temperatures, and afternoon breeziness. Hot
conditions caused by rising temperatures are standard fare for the
Desert Southwest in mid-late June. High temperatures today will
rise above normal by a few degrees with moderate Heat Risk
spreading into our southern desert areas including southern
Mohave and southern San Bernardino counties, the lower portions of
the Colorado River Valley, and Death Valley where temperatures
around 110 degrees will be common this afternoon. Temperatures
continue to increase on Friday and plateau over the weekend at
about 6-8 degrees above normal. Moderate Heat Risk expands in
areal coverage on Friday then becomes more widespread over the
weekend with areas of major Heat Risk appearing in southeast Inyo
County and southern Nye County over the weekend. Its likely the
increasing moisture drawn northward from Alberto will produce
enough cloud cover to maintain moderate Heat Risk across our
southern deserts.

For the past two days had some concern for `excessively hot`
temperatures occurring over the weekend as a massive ridge
currently over the eastern/central US migrated back west,
repositioning itself over the Desert Southwest. Now with more
moisture expected to advect into the region, NBM temperatures have
moderated some. Yesterday, NBM probabilities of Las Vegas high
temperatures 110+ were 60%-70%, today have now dropped to around
40%. In actual numbers, both Saturday and Sunday highs are now 2-3
degrees lower than yesterday. Therefore, not as many pockets of
`Major` HeatRisk expected. But, again that heat will be offset by
higher humidity values.

With limited Heat Risk concerns through the weekend, we will be
primarily focused on any potential impacts that a remnant
tropical system could bring to the Desert Southwest.

Tropical Storm Alberto, near the Mexican coast in the southwest
Gulf of Mexico, is progged to move inland into mainland Mexico
this morning. The remnants of Alberto will then continue to move
west into the eastern Pacific along the southern periphery of a
strong subtropical ridge expanding westward over the Desert
Southwest. Moisture presently over west Texas, New Mexico and
northern Mexico will advect westward underneath the ridge on east-
southeast winds, arriving into eastern Arizona today. That
moisture continues to move west into western Arizona, southern
Nevada and eastern California Friday into early next week. As the
remnants from Alberto cross into the eastern Pacific and southern
Gulf of California it could induce a gulf surge transporting
additional moisture into the lower Colorado River Valley. Both the
GEFS and EPS both indicate precipitable water values peaking over
the weekend into early next week with values ranging from 1` to
1.5` from around Las Vegas/Mesquite south through western Arizona
and eastern California. Therefore, the chance for showers and
thunderstorms has continued to increase, and expand further west
from Friday into early next week. Initial storm conditions will
likely support gusty winds and dry lightning potential, as
moisture deepens storms should transition to seeing more rain
reach the ground.
-- End Changed Discussion --

&&

.AVIATION...For Harry Reid...Diurnal winds continue with
light winds favoring southwest until mid-morning when northeast to
east winds will prevail through midday when wind will transition
though southeast settling on the south-southwest by 22Z. After the
southwest shift, speeds will increase to 10 to 12 knots with a few
gusts to 20kts possible through sunset when winds will relax a bit
to 5-8kts and become more westerly. Skies will remain mainly clear
through the TAF period.

For the rest of southern Nevada, northwest Arizona and southeast
California...Winds will follow a typical diurnal pattern through
Thursday with light and, at times, variable winds during the morning
hours. Winds will pick up from the south in the afternoon Thursday
with the gusts of around 20kts up the Colorado River Valley and west-
southwesterly gusts to 25 kts at KDAG. Skies will be clear through
the TAF period at most sites with some high clouds AOA 15kft along
the Sierra crest and over the northern Owens Valley including KBIH.
region.

&&

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

&&

$$

UPDATE...Stessman
SHORT TERM...Salmen
LONG TERM...Pierce
AVIATION...Berc

For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter