Flash Flood Warning 15, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
1043 AM PDT Thu Jul 18 2024

.SYNOPSIS...Increasing monsoonal moisture will lead to greater
thunderstorm coverage today. Otherwise, hot temperatures will
continue with temperatures climbing into the weekend. Daily
thunderstorm chances will continue as well, especially across the
higher terrain.

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.UPDATE...

Convective activity has begun across northwest Clark County and
southern Nye County. Thunderstorms will increase in coverage
through the afternoon hours before diminishing after sunset.

&&

.PREV DISCUSSION...155 AM PDT Thu Jul 18 2024...

.SHORT TERM...Today.

Monsoonal moisture will spread westward today as flow aloft
becomes more southerly on the western periphery of the Four
Corners high. Convection on Thursday overachieved a bit in
Northwest Arizona with reports of strong winds and over an inch of
rain in Meadview. Instability is forecast to be a little greater
today, so locally strong wind gusts and pockets of heavy rainfall
will again be a possibility. Tonight's 00z HREF suggests the most
robust storm development across Clark and Mohave Counties through
early afternoon, with activity spreading northward into the
evening hours. More isolated activity is possible further west.
HREF is also suggesting the potential for gusty winds (70% chance
of gusts over 35 mph, and 10% chance of over 58 mph) near Barstow
and Las Vegas. This would make sense given DCAPE values in the
1500-1800 j/kg range. Activity will tend to wane after sunset.
Aside from the uptick in storm activity, temperatures will remain
well above normal areawide.

.LONG TERM...Friday through next Thursday.

Heat will begin to increase Friday across our southern zones as
high pressure begins to intensify and move westward. This will
yield pockets of high heat risk across the Colorado River Valley
and Mohave County. Temperatures will heat up further over the
weekend as the upper-level ridge of high pressure amplifies over
the Western US. These increasing temperatures will yield Major to
Extreme HeatRisk for the valleys and lower elevations of southern
Nevada, northwestern Arizona, and southeastern California.
Elevated surface dewpoints and lingering overnight cloud cover
will also ensure nighttime temperatures remain quite warm,
offering limited relief. With confidence remaining high on the
upcoming hot weather, went ahead and upgraded the Excessive Heat
Watch to a Warning for much of the area

Hotter than normal temperatures will continue into next week as
high pressure remains positioned over the area. With the upper-
level ridge trapping moisture over the area, isolated to scattered
showers and thunderstorms will be possible each afternoon into
early next week. Forecast confidence decreases beginning around
Tuesday due to uncertainty with how our ridge will interact with a
shortwave trough as it approaches the Pacific Northwest.

&&

.LONG TERM...Friday through next Thursday.

Heat will begin to increase Friday across our southern zones as
high pressure begins to intensify and move westward. This will
yield pockets of high heat risk across the Colorado River Valley
and Mohave County. Temperatures will heat up further over the
weekend as the upper-level ridge of high pressure amplifies over
the Western US. These increasing temperatures will yield Major to
Extreme HeatRisk for the valleys and lower elevations of southern
Nevada, northwestern Arizona, and southeastern California.
Elevated surface dewpoints and lingering overnight cloud cover
will also ensure nighttime temperatures remain quite warm,
offering limited relief. With confidence remaining high on the
upcoming hot weather, went ahead and upgraded the Excessive Heat
Watch to a Warning for much of the area

Hotter than normal temperatures will continue into next week as
high pressure remains positioned over the area. With the upper-
level ridge trapping moisture over the area, isolated to scattered
showers and thunderstorms will be possible each afternoon into
early next week. Forecast confidence decreases beginning around
Tuesday due to uncertainty with how our ridge will interact with a
shortwave trough as it approaches the Pacific Northwest.

&&

.AVIATION...For Harry Reid...Partly cloudy skies along with light
winds this morning. Showers and thunderstorms will start to develop
on the higher terrain south and west of the valley by noon. The
forecast gets challenging during the afternoon when showers and
thunderstorms begin to develop within the valley associated with
gusty outflow winds. Initially, outflow winds look to approach from
the south, then afterwards outflow winds could potentially come from
any direction. Conditions look to improve after 02Z late this
afternoon as the showers and thunderstorms weaken. Partly to mostly
cloudy skies overnight with typical south-southwest wind less than 7
kts. Friday conditions looking very similar, with thunderstorms over
the mountains in the approach corridors and a low chance (<20%)
chance of a thunderstorm at the terminal.

For the rest of southern Nevada, northwest Arizona and southeast
California...Expect an uptick in thunderstorm coverage this
afternoon over southern Nevada and eastern California, with the
highest chances (40-60%) in northwest Arizona. Primary hazard with
these storms will be gusty outflow winds up to 40 mph. Local gusts
of 40 to 50 mph could impact terminals in southern Nevada and around
KDAG. Restricted visibility due to locally heavy rain is possible as
well. Very similar conditions are likely Friday, with the main
concerns again being erratic, gusty winds as well as terrain
obscuration due to locally heavy rain.

&&

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

&&

SHORT TERM...Outler
LONG TERM...Stessman
AVIATION...Pierce

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