Severe Thunderstorm Warning 33, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
1249 PM PDT Sat Sep 7 2024

.SYNOPSIS...Thunderstorm chances will increase this weekend,
particularly along and south of I-15 where there will be a threat
for strong outflow winds this afternoon and evening. Drier
conditions return by Tuesday, and temperatures will fall to mid-
September normals late in the week with a return of gusty winds.

&&

.SHORT TERM...through Monday.

High based convection is underway early this afternoon with
isolated development noted on radar near Mountain Pass and across
the southern McCullough range. Additional activity has also begun
to develop in the Hualapais across Mohave County. Little change
is expected to the overall thinking, with continued storm
development mainly south of Las Vegas that will tend to develop
southward towards the Colorado River Valley. DCAPE values of
1500-1800j/kg present across much of the Mojave Desert and
Colorado River Valley suggest localized instances of damaging
winds will be possible with the stronger storms and microburst
activity. Flash flood risk remains low, though some sensitive
drainages around Needles and the Mohave Valley could see pockets
of flash flooding if colliding outflow boundaries force some
locally stronger storms in that area this evening.

Similar conditions will again be in play tomorrow, though moisture
will continue to advance north into the southern Great Basin. This
mornings 12z HREF along with the latest NBM PoPs depict higher
probabilities tomorrow for storm activity across Clark and Lincoln
Counties, especially across the Spring Mountains.

By Monday, moisture will begin to shift eastward as flow aloft
turns more southwesterly, but scattered storms will remain
possible in Mohave County. Aside from the storm chances,
temperatures will remain above normal through early next week.

.LONG TERM...Tuesday through Friday.

Approaching Pacific trough will be the main focus of the long
term which promises to bring a sharp cool down midweek along with
a return of gusty winds to the region. On Tuesday, a light
westerly flow aloft will be in place keeping conditions fairly
benign with continued above normal temperatures and light winds.
However, a deep early season trough will be approaching the
Pacific Northwest coast and crash into the western US/Great Basin
by Wednesday afternoon. This will send a belt of strong westerlies
southward as well as drop a sharp cold front through the region
Wednesday into Thursday. Temperatures will drop to near normal on
Wednesday before falling a few degrees cooler than normal Thursday
and Friday behind the departing trough. While there remains minor
discrepancies among model guidance on the finer details of the
troughs strength and exact timing, confidence continues to
increase in a more fall like pattern next week featuring cooler
and windier conditions.

&&

.AVIATION...For Harry Reid...Prevailing winds shift from the
northeast to the southeast this afternoon. Thunderstorms development
is expected southern Nevada this afternoon and evening. Brief
rainfall and lightning cannot be ruled out between 21Z and 01Z at
KLAS, the most favorable timeframe for storms to reach the terminal.
Gusty and erratic outflow winds up to 30 knots may also reach the
terminal during that time even if the storms are distant. Winds
should be out of the south to southwest with speeds under 10 knots
by the evening. Additional thunderstorms may also develop near Las
Vegas tomorrow afternoon, with similar threats of lightning and
gusty outflow winds.

For the rest of southern Nevada, northwest Arizona and southeast
California...The primary weather concern today is scattered storms
across most of the forecast area. Thunderstorms cannot be ruled out
this afternoon in the Las Vegas area including KVGT and KHND, and
development in the evening is possible along the Colorado River
including KEED and KIFP. Storm activity may bring lightning, brief
rainfall, and gusty erratic outflow winds up to 30 knots to the
terminals. Precipitation is also possible in the Owens Valley near
KBIH, but outflow winds should be less intense. Outside of storms, a
general diurnal wind pattern is expected with FEW to SCT clouds at
or above 12 kft.

&&

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

&&

DISCUSSION...Outler
AVIATION...Meltzer

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