Severe Thunderstorm Warning 5, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
1124 AM PDT Sat Jul 13 2024

.SYNOPSIS...A monsoonal pattern is in place and thunderstorms are
possible across most of the area today and tomorrow. These storms
may bring gusty winds, frequent lightning, and heavy rainfall.
Thunderstorms become more isolated next week as drier air filters in
from the west. Additional moisture and cloud cover will help
moderate temperatures but afternoon highs will still remain several
degrees above average.

&&

.UPDATE...The surge of monsoonal moisture has arrived with this
morning's sounding boasting an impressive 1.14 inches of
precipitable water in the atmosphere. That is around 150% of normal
for this time of year and is up from the 0.62 inches of precipitable
water present in the atmosphere yesterday afternoon. This anomalous
moisture is already helping to fuel showers and thunderstorms in
Mohave County with current radar imagery showing a line of
convection running parallel to US 93 northwest of Kingman. As this
morning's clouds continue to clear out and the surface is able to
heat up we will see the continued development of showers and
thunderstorms across the region this afternoon and evening.

The inverted V shape in the lower levels of the atmosphere on this
morning's sounding, combined DCAPE values of 1,800+ J/kg indicate
that gusty outflow winds will be a threat from any storms that
develop. The aforementioned inverted V shape on this morning's
sounding also shows just how dry the lower levels of the atmosphere
are even with this anomalous moisture in place. These dry lower
levels will make it difficult for precipitation to make it to the
ground, which when combined with lightning produced by these storms
results in an increased dry lightning threat. The dry lightning
threat combined with critical fuels across the southern Great Basin
has prompted the issuance of a Red Flag Warning for portions of
Esmeralda, Nye, and Lincoln counties in Nevada for this afternoon
and evening.

Tomorrow will bring another round of showers and thunderstorms to
portions of the area as moisture remains in place. This moisture
combined with cloud cover from vicinity convection will keep
temperatures a few degrees cooler than they have been, with
afternoon high temperatures around  to 5 degrees above normal.

&&

.SHORT TERM...through the weekend.

The position of a strong 500 mb high centered over the Four Corners
brings southeasterly to southerly winds aloft, a pattern favorable
for monsoonal moisture advection into Arizona, Nevada, and eastern
California. Increased moisture on sounding profiles supports CAPE
between 500 and 1000 J/kg with the greatest values around the
Nevada, Arizona, and California tripoint. PWAT values rise to the 1
inch to 1.4 inch range in Mohave, Clark, and San Bernardino
Counties, and the .7 to 1 inch range in areas further to the north.
This moisture is 120 to 150 percent of normal for this time of year.
However, a closer look at forecast soundings indicates persistent
dry air at the surface and most of the moisture aloft. Cloud bases
of around 10 kft or higher and dry low levels yielding 2000 J/kg
DCAPE mean strong outflow winds are a threat with any storms that
form this weekend, as seen with storms that already occurred over
the past two days. Blowing dust along outflow boundaries is also
possible, which will reduce visibility and create dangerous
travel conditions. HREF shows a 30 to 60 percent chance of gusts
reaching at least 40 mph with storms this afternoon. A secondary
threat for Mohave County is isolated and brief heavy rainfall
which could cause flash flooding. WPC placed a Marginal (5
percent) risk for excessive rainfall for both today and tomorrow
in eastern Mohave County. Rainfall totals up to .3 inch are
possible under the strongest cores, particularly over high terrain
where orographic lift is greatest. Lastly, dry thunderstorms and
cured fuels on the ground bring increased fire weather concerns in
the eastern Sierra and Owens Valley where a Red Flag Warning is
in place. See the Fire Weather section for more details. Storm
activity today and tomorrow will begin in the late morning and
early afternoon, increasing in coverage through the afternoon,
then tapering off overnight.

Relatively lower temperatures compared to earlier this week bring
HeatRisk down into the Moderate (Level 2) for most areas this
weekend. Afternoon highs remain several degrees above average.

.LONG TERM...Monday through Friday.

A ridge of high pressure will continue across the desert southwest
next week. The ridge will be positioned in a place conducive too
push a little moisture northward, but there isn't a favorable
dynamic situation to have a strong, persistent push. The monsoonal
moisture we do have in place will linger into the beginning of the
work week, mainly over southern portions of the CWA. The chance of
precipitation will be greatest Monday across eastern Mohave County
and the southern Great Basin. Drier conditions can be expected each
day through the week. While temps will remain above normal for much
of the area, conditions will be a bit cooler than we have
experienced over the past week.

&&

.AVIATION...For Harry Reid...Light winds this morning should turn
more easterly by late morning with speeds remaining below 10kts.
Convection is expected to develop over the higher terrain
surrounding the Las Vegas Valley after 19Z, and there is a 40% to
50% chance of one of the storms moving off the terrain and directly
impacting the field, with 23Z to 03Z being the time of the highest
chances. If a storm does not directly affect the field, gusty
outflow winds from nearby storms have a high (greater than 70%)
probability of causing impacts in the terminal area.  Any
thunderstorms could bring lightning, brief rain, and sudden gusty
winds. Outside of convective activity, southwest winds can be
expected into the early evening. Model guidance continues to show a
brief period of northwest winds after sunset, but winds should
return back to the southwest around midnight. Additional
thunderstorm activity is possible on Sunday, although coverage is
expected to be less than what occurs today.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered areas of convection are expected to develop
across most of the region this afternoon and evening, and any storms
will be capable of producing lightning, brief rain, CIGs to 10kft,
and sudden gusty outflow winds. Guidance also indicates that storms
near KDAG this afternoon have a greater than 60% chance of
generating gusty outflow winds that could spread northward into the
Owens Valley during the late afternoon and evening, possibly
reaching KBIH between 00Z and 02Z. Away from areas of convection,
south to west winds around 12kts and occasional gusts to 20kts can
be expected. The thunderstorm activity should diminish after sunset,
and winds should fall below 10kts across the region overnight.
Additional thunderstorm activity is possible on Sunday, although
coverage should be less than what is seen today and be mainly over
southern Nevada and northwest Arizona.

&&

.FIRE WEATHER...Thunderstorms will increase in coverage across much
of the region today and tomorrow as improved monsoon moisture works
its way into the area. However, high storm bases and dry air near
the surface mean any storms that form may produce gusty and erratic
outflow winds and little precipitation at the surface. Dry
thunderstorms are particularly a concern across western Inyo County
where a Red Flag Warning remains in effect for the Sierra and Owens
Valley. Additional dry thunderstorms also cannot be ruled out in
sections of Esmeralda, Nye, and Lincoln Counties.

&&

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

&&

UPDATE...Stessman
SHORT TERM...Meltzer
LONG TERM...Berc
AVIATION...Planz

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