462
FXUS65 KVEF 151541
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
841 AM PDT Mon Jul 15 2024

.SYNOPSIS...Another day of scattered thunderstorms is in store
today before drier air works in from the west and thunderstorm
coverage decreases through late in the week. High pressure will
build westward over the weekend with temperatures heating up and
lingering isolated thunderstorm activity expected.

&&

.UPDATE...Seeing a few light radar returns in far NW Clark and SE
Nye Counties this morning, drifting north towards the National
Security Site. Based on area webcams, this is predominantly virga,
but it`s possible a few drops are reaching the ground. Elsewhere,
skies are clear or are beginning to clear, setting the stage for
another round of convection this afternoon. Latest morning CAMs
suggest the bulk of thunderstorm activity will be south of I-15 and
in northern Lincoln County, with more isolated activity elsewhere.
Localized flash flooding will once again be possible today,
primarily in the Twentynine Palms area and central Mohave County.
Rain chances slowly wane and become mostly confined to the eastern
half of the CWA by mid-week, but never truly go away before
increasing over the weekend.

&&

.SHORT TERM...through Thursday.

Early morning satellite imagery depicts considerable mid-level
moisture trapped beneath a strong high pressure ridge over the
Four Corners region. An elongated band of mid-level clouds
extends from western Clark County south to near Twentynine Palms
and radar is depicting some very light shower activity along this
axis, though no lightning activity. This activity will continue to
drift north through the morning hours but is unlikely to result
in much more than sprinkles given the still relatively large
dewpoint depressions in play.

Heading into the afternoon hours, not much has changed since
yesterday and we will still be dealing with precipitable water
anomalies of 100-150% across the region. Light southerly steering
flow will favor terrain driven storms drifting north but also
developing along outflow boundary collisions heading into the
afternoon and evening hours. 00z HREF guidance favors at least
some degree of gusty winds with the storms forming, with 50-70
percent probabilities of 30+ knot wind gusts along the I-15
corridor and extending south to Twentynine Palms. With anomalous
moisture and slow storm movement, some of the more robust storms
will also be capable of flash flooding. Most favored areas for
storms today appear near Twentynine Palms again, and across
southern Clark County extending south into the Mojave Preserve,
with more isolated activity elsewhere.

A subtle southwesterly flow intrusion will bring some drier air
into our northwestern zones Tuesday through Thursday, but points
further east will only see a very slight decrease in atmospheric
moisture content with a continued weak southerly flow around the
high to our east. This will keep daily storm chances going across
our eastern zones, namely Lincoln, Clark, eastern San Bernardino,
and Mohave Counties. Storms will favor the higher terrain, but
southerly steering flow could drift storms into the valleys during
the late afternoon and evening hours. Aside from the storm
chances, temperatures will be heating back up a few degrees as
cloud cover decreases, however, regional heat risk remains solidly
in the moderate category through Thursday.

.LONG TERM...Friday through early next week.

Four corners high will build westward Friday through the weekend
threatening to warm temperatures back to excessive levels. Heat
Risk rises to the high category on Friday across the Las Vegas
metro and lowest desert elevations, and increases in coverage
further on Saturday and Sunday. This may lead to an eventual
consideration of an Excessive Heat product - however, monsoonal
moisture never really gets flushed out of the region, and will
begin to reload into the area while the high builds west. This
complicates the forecast considerably as convective complexes in
Arizona could result in noteworthy cloud cover impacts and
sporadic surges in low level moisture. So for now, it remains a
period of greater uncertainty, with extended range guidance
suggesting increasing levels of monsoonal moisture arriving by
early next week.

&&

.AVIATION...For Harry Reid...Light winds this morning will turn to
the east-southeast by early afternoon. There could be some
variability in the easterly winds, but directions should fall
between 090 and 130. Scattered areas of convection are expected this
afternoon, with the storms initially developing over the higher
terrain surrounding the valley after 20Z. After 21Z, there is a 30%
to 40% chance of storms moving off the terrain and directly
impacting the field. Even if storms do not directly impact the
field, outflow winds from nearby storms could bring periods of
gusty, erratic winds to the terminal area. Storms should end by
early evening, and light westerly winds are expected after sunset.
Isolated storms are possible again on Tuesday, but the majority of
the activity should be confined to northwest Arizona.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered thunderstorms are expected across most of the
region again today. Storms should begin to develop after 19Z and
persist through sunset before decreasing. Any storms will be capable
of producing lightning, brief periods of heavy rainfall, CIGs less
than 10kft that could obscure areas of higher terrain, and sudden
gusty outflow winds.  Away from areas of convection, south-to-west
winds 10kts to 15kts with occasional gusts to 20kts are expected.
The thunderstorm activity should diminish after sunset, with winds
falling below 10kts across most of the region overnight. Additional
thunderstorms are possible on Tuesday, but coverage is expected to
be more limited, with the majority of the activity remaining over
northwest Arizona and the higher terrain north and west of the Las
Vegas Valley.

&&

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

&&

$$

UPDATE...Woods
DISCUSSION...Outler
AVIATION...Planz

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