Area Forecast Discussion
Issued by NWS Las Vegas, NV

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049
FXUS65 KVEF 171728
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1028 AM PDT Wed Jul 17 2024

.SYNOPSIS...Heat will be the primary weather story through the
weekend as a large high pressure center moves overhead. Isolated
thunderstorm activity will remain a possibility as well, mainly in
Northwest Arizona today, but spreading into the eastern Mojave
Desert Thursday onward. Temperatures will soar to excessive heat
levels over the weekend. Greater storm chances are suggested
early next week as a deeper push of moisture arrives in the area.

&&

.UPDATE...Mainly quiet weather conditions across the region this
morning with plenty of sunshine, light winds, and warm
temperatures. Surface observations this morning reveal a dewpoint
temperature gradient decreasing from southeast to northwest across
the region with low to mid 50s being reported across southern
Mohave County into the Colorado River Valley and dewpoint temps in
the 30s across our far northwest areas.

At 10 am, a few cumulus clouds were already building over the
mountains with a few lightning strikes already noted in northeast
Mohave and eastern Lincoln counties. The highest instability
this afternoon is forecast over Mohave County and eastern Lincoln
County where the probability for CAPE exceeding 500 j/kg is
forecast. Expect scattered storms to develop in these areas today
with more isolated type convection over the Spring Mountains and
across portions of southern Clark and northeast San Bernardino
counties. For the Barstow and the Morongo Basin areas, an isolated
cell or two can`t be ruled out for today. Along with dangerous
lightning, storms today will be capable of producing brief heavy
rain and gusty outflow winds.

&&

.PREV DISCUSSION...200 AM PDT Wed Jul 17 2024...

.SHORT TERM...through Thursday.

High pressure center currently settled across western New Mexico
will expand westward over the coming days with a slightly
strengthening southerly steering flow developing over the region.
This will ensure hot temperatures continue, as 594dm heights
spread further west. Unlike a couple weeks ago, this high pressure
center is no longer extremely dry and instead has fairly
considerable moisture trapped beneath it. This is resulting in
elevated surface dew points generally in the 40s and low 50s
across the region. This will add a little more kick to the heat
via a slightly higher apparent temperature, and limit nocturnal
cooling potential to some degree. The elevated atmospheric
moisture will also promote continued thunderstorm activity,
mainly across northwest Arizona today but perhaps spreading into
eastern San Bernardino county and southern Nevada tomorrow
afternoon.

.LONG TERM...Friday through Wednesday.

High pressure migrates west Friday and becomes centered over
Nevada over the weekend, maintaining above average high
temperatures across the area. Major (Level 3) to Extreme (Level 4)
HeatRisk returns to much of the forecast area including Las Vegas
through the weekend and despite concerns about cloud cover and
precipitation influences, went ahead with an Excessive Heat Watch
given the intensity of the high that will be parked overhead.
Beyond Sunday, there are indications of deeper moisture attempting
to encroach on the area leading to larger uncertainty in how long
the heat will last.  Additionally, Low pressure over the Pacific
Northwest and a trough over the Midwest may influence the position
and intensity of the ridge, adding to the uncertainty. PWATs over
100 percent of normal will remain in place under the ridge and
there will be daily afternoon and evening thunderstorm chances
into early next week in the central and eastern sections of the
forecast area where instability is the greatest. Stable air over
the western sections of the forecast area (Inyo and western San
Bernardino Counties) reduces the likelihood of storm activity in
those areas. Moisture and cloud cover may also help mitigate the
heat going into next week.

&&

.AVIATION...For Harry Reid...Winds will primarily follow a
diurnal pattern, with light and variable winds this morning becoming
to southerly in the mid to late afternoon. Winds will be less than
10 kts. There is a low (20-30%) probability of thunderstorms on the
Spring Mountains, Sheep Range, or McCullough Range producing an
outflow boundary which impacts winds at the terminal in the late
afternoon or evening hours. For Thursday, thunderstorms increase and
will not be limited to the higher terrain. There will be a risk of
outflow winds from thunderstorms, but otherwise diurnal winds should
prevail.

For the rest of southern Nevada, northwest Arizona and southeast
California...Thunderstorm chances will increase marginally over
Clark and Mohave Counties today and will favor eastern Mohave
County, with an increased the risk of outflow winds being pushed
farther to the west and into KIFP and KEED during the late afternoon
and evening hours. Away from thunderstorms, expect VFR conditions
with winds near or below 20 knots. Thunderstorm chances will
increase areawide on Thursday.

&&

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

&&

$$

UPDATE...Salmen

SHORT TERM...Outler
LONG TERM...Meltzer
AVIATION...Czyzyk

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