021
FXUS65 KVEF 181916
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1216 PM PDT Sat Jul 18 2026

.KEY MESSAGES...

* Monsoonal moisture remains in place over the region through next
  week, maintaining daily thunderstorm chances.

* Seasonably hot temperatures continue, though little relief will
  be felt overnight as moisture and cloud cover result in mild low
  temperatures.

&&

.DISCUSSION...

Early this afternoon, isolated convection has already started
forming over the higher terrain of southeastern Nevada and
northwestern Arizona, with additional development expected through
this afternoon and into this evening. Overall, coverage is
expected to be less than what was observed on Friday afternoon and
evening, through locally heavy rain and flooding remain concerns,
especially for any locations that received appreciable rainfall
previous days. Instability is expected to generally range from 500
to 1000 J/kg, maximized across southern Mohave County. However, 0
to 6 km shear remains weak, around 10 to 20 KT, which will result
in slow storm motion and additional convective development away
from the higher terrain largely dependent on outflow boundary
interactions. Additionally, while DCAPE has decreased
substantially over the last week due to the influx of monsoonal
moisture, model soundings still indicate locations across Lincoln,
Clark, and Mohave Counties with around 500 to 1000 J/kg of DCAPE,
so gusty downburst winds also remain a threat with the stronger
storms that develop. Convective activity will begin waning after
sunset, though storms over southwestern Utah this evening could
send outflow boundaries southwestward across northern Mohave,
southern Lincoln, and into Clark County/the Las Vegas Valley
tonight. A similar set-up is expected on Sunday, though showers
may develop during late morning, with a westward expansion of
thunderstorm chances during the afternoon and evening.
Thunderstorms remain in the forecast each day through the upcoming
week, especially across northern and eastern portions of the
forecast area as precipitable water values remain 2 to 3 standard
deviations above normal. Ensembles indicate a weak inverted
trough/easterly wave that will translate westward midweek,
potentially resulting in an uptick in thunderstorm activity
Wednesday into Thursday. Thereafter, there is quite a bit more
uncertainty in the evolution of the upper pattern as a trough
takes shape off of the Pacific Northwest, which could, in turn,
displace the ridge over the Four Corners Region, so stay tuned.

In addition to daily thunderstorm chances, each day through next
week will also remain hot and muggy. While afternoon high
temperatures will be near seasonal normals, the abundant moisture
and lingering overnight cloud cover due to afternoon and evening
thunderstorms will maintain above normal low temperatures. Thus,
little relief will be felt overnight, and we will continue to
observe widespread Minor and Moderate (Level 1 and 2) Heat Risk
each day. Those who will be outdoors will need to ensure they stay
hydrated and take breaks in the air conditioning whenever
possible.

&&

.AVIATION...For Harry Reid...For the 18Z Forecast Package...
Convection chances and coverage this afternoon and evening will be
limited, with any thunderstorms remaining mainly over the higher
terrain surrounding the valley. Some guidance suggests a push of
northeast winds from storms over southern Utah possibly moving into
the valley after 04Z, although the chance of this occurring is
around 30 percent. Regardless of whether the northeast push occurs,
typical diurnal southwesterly winds are expected after 07Z. Away
from any convection that does develop over southern Nevada, VFR
conditions will prevail with SCT clouds and bases remaining AOA
10kft AGL into Sunday. Convective coverage over southern Nevada is
expected to increase on Sunday.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 18Z Forecast Package...Light south to west
winds of less than 10 knots are expected across much of the region
through tonight. One exception will be in the northern Owens Valley,
including KBIH, where southerly winds gusting to around 20 knots are
expected this afternoon. KDAG will also see the typical increase in
westerly winds after sunset. Convection will be more limited across
the region today, with most storms remaining over the higher terrain
in Clark, Lincoln, and Mohave counties. An isolated storm also
cannot be ruled out over the eastern Sierra slopes in northern Inyo
County. Any convection that does develop will wane after sunset and
light winds favoring typical overnight patterns should prevail
tonight. Away from convection, VFR conditions will prevail with SCT
clouds and bases remaining AOA 10kft AGL into Sunday. Convective
coverage over southern Nevada and northwest Arizona is expected to
increase on Sunday.

&&

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

&&

$$

DISCUSSION...Phillipson
AVIATION...Planz

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