Severe Thunderstorm Warning 1, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
721 PM PDT Thu Apr 17 2025

.SYNOPSIS...A storm system will continue to bring shower and
thunderstorm activity as well as strong winds for the rest of today
and tomorrow. Calmer weather and warmer temperatures are expected to
return next week.
&&

.UPDATE...A cold front was draped across Inyo County through
Southern Nevada this evening, which was very evident by the extreme
dewpoint gradient in that area. Along the front, scattered showers
and thunderstorms developed as moisture pooled ahead of the front
and a digging upper level trough in Utah. Other than lightning, no
significant impacts were reported with the thunderstorms as rainfall
amounts remained under 0.10 inch due to dry air near the surface.
Occasional gusty winds of 30-40 MPH were also reported with some of
the showers and thunderstorms, however the gradient winds were just
as strong was southwest winds ahead of the front then northwest
winds behind the front gusted 25-35 MPH. Further south, light radar
returns were noted as the deformation zone that was over the
Southern Great Basin last night shifted southeast, but precipitation
was very light and no lightning was reported.

Scattered showers and thunderstorms have waned in Inyo County as the
main trough shifted away and forcing decreased. This trend will
continue and any precipitation will end in Inyo County in the next
few hours. Further east in northeast Clark and northern Mohave
County, the trough axis will be more robust and thus continued
precipitation is possible through the night. Te best chance for
showers and thunderstorms through the early part of the night will
be in northern Mohave County, with lesser chances in Clark County.
The second half of the night should be drier as precipitation shifts
into central Arizona, though lingering light showers may continue in
far eastern Mohave County into Friday morning. Elsewhere, it will be
dry. Continued gusty west winds 35 to 40 MPH are expected around
Barstow, CA through at least midnight before winds begin to diminish-
 a wind advisory remains in effect for the Western Mojave Desert
through early Friday morning. The other area where winds will
continue to be gusts and potentially impactful is in Esmeralda and
central Nye County where gusty northwest winds to around 40 MPH have
been reported this evening. These winds may decrease somewhat
overnight to 20-30MPH however this lull will be short lived as gusts
over 40 MPH will return Friday early morning.

-Nickerson-
&&

PREVIOUS DISCUSSION...252 PM PDT Thu Apr 17 2025
.SHORT TERM...Through Friday Night.

An upper level low is currently centered over northern Utah with a
trough axis extending southwest into southern California. A surface
cold front extends across the southern Great Basin and is expected
to progress south and east today and tomorrow. Light rain showers
have already begun in Las Vegas and parts of northwestern Arizona
ahead of the front, but little precipitation is reaching the ground.
Meanwhile, a stronger band of precipitation is moving southeast
through Lincoln County in a region of over 1000 J/kg SBCAPE. It
appears relatively more impressive on satellite and radar and is
producing lightning. More substantial bands of precipitation are
expected to develop this afternoon and evening as the front moves
southeast into an area of greater moisture. PWATs are close to 200
percent of normal for this time of year, but that only translates to
out to around .5 inch of PWAT since it is the dry season. Valley
rainfall totals should be just a few hundreths of an inch at most
and between .1 and .2 inch on high terrain. Cold air aloft and 500
to 1000 J/kg SBCAPE suggest that small hail cannot be ruled out. The
most likely threat from these storms appears to be strong outflow
winds. Forecast soundings show a high based inverted-V pattern and
SPC mesoanalysis shows 500 to 1000 J/kg of downdraft CAPE. High
resolution guidance indicates potential for outflow gusts up to 50
mph. The low drops south into Arizona tomorrow and shifts east,
limiting most precipitation potential to the higher terrain in
Mohave County. A few isolated wrap around showers may develop
in southern Nevada as well. Totals should remain light.

The other forecast challenge is wind. Ahead of the front,
southwesterly winds with peak gusts between 25 and 35 mph have
persisted throughout the day. The strongest gusts are in western San
Bernardino County, where a Wind Advisory remains in effect through
tonight. Northwesterly winds gusting to 30 to 40 mph have developed
behind the front in Esmeralda and central Nye Counties, and a Wind
Advisory is also in effect for those counties through tomorrow
evening. Lastly, issued a Wind Advisory that will go into effect for
Owens Valley and Death Valley tomorrow morning as postfrontal winds
intensify in those locations.

.LONG TERM...Saturday through Wednesday.

The closed low will shift east Saturday, with the area remaining
under northerly flow aloft behind the exiting system. This will pump
dry air into the region and put an end to any precipitation chances.
The pressure gradient will decrease through the day, so breezy north
winds will be strongest in the morning with gusts around 20 MPH that
will drop off areawide by the afternoon. Weak height rises will
result in warmer temperatures compared to Friday, with high
temperature rising to near or slightly below normal.

The weather pattern will remain progressive by generally low impact
Sunday through early next week. Occasional shortwaves will move
through the mean flow but they will be weak and have little to no
moisture to work with so precipitation will be limited to none
Sunday through Wednesday. Occasionally increases in winds is
possible as each piece of energy moves through, but none should be
strong enough to result in strong, impactful winds. Temperatures
will climb back above normal on Sunday with high temperatures
climbing to 10-15 degrees above normal in many locations.
Temperatures will then remain around that same level through much of
next week.

&&

.AVIATION...For Harry Reid...For the 00Z Forecast Package...Winds
will be south to southwest with gusts of 25-30 kts expected through
the early evening hours. Light showers will be in the vicinity of
the terminal through the evening (04Z). The primary aviation concern
is the potential for a broken line of thunderstorms to impact the
terminal as a cold front moves through the region between 01-04Z.
The confidence with the thunderstorm activity has decreased during
the afternoon but with any thunderstorm, erratic, gusty outflow
winds are expected (wind gusts 40+ kts). If a storm moves over the
terminal, brief heavy rain could produce ceilings around 5-8kft,
along with brief reductions in visibility. After the front and
thunderstorms move south of the terminal, conditions improve, with
gusts diminishing after 05Z as winds shift to the northwest. After
daybreak Friday, gusty conditions return, with northwesterly winds
continuing into Friday evening.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 00Z Forecast Package...Elevated and at least
intermittently gusty southerly to southwesterly winds are expected
at area terminals through early this evening, with gusts to 20-25
kts common. Exceptions include KBIH, where winds will remain
northerly to northwesterly through the forecast period, and KDAG,
where stronger west-southwest winds with gusts to 30-35 kts are
expected. The primary aviation concern is an approaching cold front
and associated showers and thunderstorms that will move southward
through the region this evening. Thunderstorm activity will be
favored over Lincoln and Mohave Counties as well as the southern
half of Inyo County. The chance of thunderstorms at any of the LV
has been decreasing but is most likely at any of the terminals
between 01-05Z, there is higher confidence with showers in the
vicinity of all terminals. Behind the front tonight, conditions
improve with winds shifting to the north/northwest, with gusts
gradually diminishing and sustained wind speeds dropping to 10 kts
or less. Stronger northerly winds will redevelop on Friday.

&&

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

&&

SHORT TERM...Meltzer
LONG TERM...Nickerson
AVIATION...Czyzyk

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