Heat in Nevada, June 1 to 4, 2025

Area Forecast Discussion
National Weather Service Las Vegas NV
1025 PM PDT Sat May 31 2025

.SYNOPSIS...The Extreme Heat Warning continues until this evening
for sections of the Mojave Desert as high pressure maintains hot
temperatures. Afterwards, tropical moisture will bring cloud
cover, increasing chances for precipitation, and relatively cooler
temperatures starting Sunday through the middle of next week. The
greatest precipitation amounts appear to be across northwestern
Arizona on Sunday into Monday.
&&

.UPDATE...Four daily record high temperatures were set today: Las
Vegas (105), Bishop (101), Barstow-Daggett (106), and Desert Rock-
Mercury (102), while two daily record warm low temperatures are
currently on-track to be set: Las Vegas (85) and Death Valley (95).
The Extreme Heat Warning will be allowed to expire on time at 11pm
PDT tonight, as substantially cooler air will move into the region
Sunday (along with precipitation chances). Watching breezy south-
southwest winds push into San Bernardino County this evening with
speeds generally between 30 and 35 mph off of an outflow produced
from storms in southeastern California.

Looking at satellite and MRMS radar imagery, a band of light, high-
based showers (read: virga) is pushing northward into our forecast
area tonight. The 00Z HRRR shows this band continuing northward
before dissipating around 14Z. Though the HRRR is likely over-
exaggerating reflectivities, it is of note that the MRMS data may be
under-exaggerating due to the Edwards Air Force Base Radar (KEYX)
being down until further notice. Regardless, this band of showers
should have minimal impact, as the low levels are dry enough to
evaporate most, if not all, rain before reaching the ground.

Shower activity formally enters the forecast area from the south
early Sunday morning and will push northeastward through the day.
Meanwhile, instability-based convection will form in the higher
terrain of the southern Great Basin with the heating of the day.
Activity will become more convective in-nature as the evening
progresses and the atmosphere fully saturates. Greatest chances of
isolated flash flooding potential remain over the far southern
zones... southeastern San Bernardino County and southern Mohave
County Sunday evening. No changes to the forecast this evening, as
it remains representative.
&&

.PREVIOUS DISCUSSION...331 PM PDT Sat May 31 2025/

.SHORT TERM...Tonight through Sunday night.

The forecast tonight through Sunday night (and even beyond into
Monday and Tuesday) is a difficult one with lots of different
pieces working off each other, plus the inherent hard time models
have with these types of set ups. In addition, this set up is
rare for this time of the year which decreases confidence further.
Short term updates and mesoscale meteorological analysis will be
necessary the next 24-48 hours as this all evolves to pin down
details with confidence.

In general, expecting a cut off low off currently off the the
southern California coast to eject into Arizona through Sunday
night, weaken as it moves northeast. This system will be wrapped up
in remnant moisture from Alvin and push anomalously high moisture
into the region. Precipitation will develop as it moves through,
with the best chances being south of the I-15 where moisture and
forcing will be greatest.

Despite increasing forcing tonight as the low shifts onshore,
precipitation will struggle as low levels remain very dry. After
isolated showers in the terrain of the southern Great Basin end
after sunset, a dry night is expected. Sunday morning after 5 AM,
there is increased uncertainty in the precipitation forecast in far
southern areas as stronger vorticity advection rotates into the
region and some weak moisture increases are noted on models;
however, it most likely will continue to be dry and there is a lot
of dry air to overcome.

Sunday morning winds will be interesting as some models show a blast
of southerly gusts of 20-30 MPH up the Colorado River Valley, which
could be associated with a surge in moisture. This further
decreases confidence in the dry forecast Sunday early morning- a
bit worried this may moisten up low levels faster than expected or
that this push of moisture and winds may act as a warm front
which could kick off high based showers and thunderstorms. So
far, hi-res models are not excited about this feature doing
anything and probabilities for impactful precipitation or winds
are little to none. Forecast soundings in the Colorado River
Valley continue to show dry air at the surface Sunday morning as
well. So most likely, it will remain dry Sunday morning. Will need
to watch this feature in case it either kicks of scattered
precipitation with the low levels remaining dry, which could lead
to sudden gusty winds due to virga...or it moistens up the low
levels earlier than expected which would increase precipitation
chances earlier in the day for southern Mohave and southeastern San
Bernardino counties.

There is better model consensus that PWATs will increase late Sunday
morning into the early afternoon. By about 4 PM Sunday, 1.00 inch
PWATs should be in place along and south of the I-15 as well as
through San Bernardino County and Death Valley. Additional waves of
vorticity advection and increased cyclonic forcing is also expected
as the center of the low moves into southern California. With
increased moisture forcing, the chances for precipitation should
also spread north through southern San Bernardino, southern Mohave,
and far southern Clark counties Sunday afternoon. In addition,
diffluence aloft in the southern Great Basin area along with upslope
easterly flow should result in additional terrain base showers and
thunderstorms Sunday afternoon. While available moisture in the
column may increase, low levels won't moisten up until late Sunday
afternoon into the evening. Rainfall amounts will be limited through
the afternoon; however, there is a threat for sudden gusty winds
over 40 MPH under any showers or thunderstorms that develop until
Sunday evening. The highest probabilities for gusty outflow winds on
HREF will be through the southern Great Basin and northern Inyo
County where there is a 50% chance for winds over 30 MPH. However,
any showers or thunderstorms through Sunday afternoon would have a
risk of gusty outflow winds given how dry the low levels will be
much of the day.

Sunday night, forecast soundings moisten and precipitation should
be able to reach the surface more efficiently. However, as the
low moves into Arizona, it will weaken and thus forcing will be
waning. Sunday night into Monday morning is the highest chance
for precipitation through the period as PWATs climb to 200% of
normal. However, with decreasing forcing, impacts will be
limited. The best chance for precipitation impacts will be in
southern San Bernardino and souther Mohave County where there is a
50% chance for rainfall totals over 0.25 inches. Brief heavy rain
is possible as forecast soundings show decent saturation along
with skinny CAPE profiles. Any training on east-west moving
precipitation bands could result in a limited flash flood threat,
which is highlighted by WPC's Day 2 marginal excessive rainfall
outlook in areas south of I-40.

With increasing moisture and decreasing heights, temperatures on
Sunday will run 5-10 degrees cooler than today. Major heat risk is
not expected in most areas on Sunday. No changes are needed to the
Extreme Heat Warning which ends tonight as temperatures cool off
after sunset.

.LONG TERM...Monday through Saturday.

Chances of precipitation linger into Monday across our eastern
zones as the vorticity maxima associated with the Baja low push
eastward across northern Arizona toward the Four Corners.
Meanwhile, a trough originating from the Pacific Northwest will
dig part of the way down the west coast before pinching off a
closed low over NorCal late Sunday into Monday. This low will
glide along the coast before moving inland on Tuesday with a
similar trajectory as the Baja low. These dynamics will tap into
remnant moisture over the area, resulting in persistent slight
PoPs across Mohave, eastern Lincoln, and eastern Clark counties
through Wednesday and will further drop temperatures by 6 to 8
degrees between Sunday and Monday.

A dry northwest flow sets up over the region mid-to-late week as an
area of high pressure grows in the east-central Pacific as well as
the southeastern Pacific. Heights will rise over the Desert
Southwest, resulting in temperatures rebounding back to above-normal
heading into next weekend.
&&

.AVIATION...For Harry Reid...For the 06Z Forecast Package...Moderate
southwest winds will continue through most of the night before
decreasing and shifting to a more southerly direction around
daybreak.  Winds will remain around 10 knots through midday before
turning back to the southwest and increasing by early afternoon.  It
should remain dry into the evening, but areas of virga from early
afternoon onward may create periods of gusty and erratic winds.
There is a better chance of convection affecting the valley tomorrow
evening after 04Z, with the best chances after 06Z.  Chances will be
even better to the south along the Peach Spring Corridor from mid-
evening on.   VFR conditions are expected through most of the TAF
period with bases remaining AOA 15kft AGL.  However, CIGs could drop
to around 10kft AGL by tomorrow evening as convection moves into the
area.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 006 Forecast Package...Conditions at the Las
Vegas area TAF sites will be similar to what is described above for
Harry Reid, except convection could affect KHND 1 to 2 hours
earlier.  At KBIH, northerly winds will continue overnight with
speeds gradually decreasing.  Scattered areas of convection are
possible during the afternoon along the Sierra and could result in
gusty, erratic winds affecting the terminal after 20Z.  A few storms
are also possible near KDAG during the afternoon, although coverage
is expected to be less and remain south of the immediate area. In
the Colorado River Valley, storms are also possible from late
afternoon onward.  The latest guidance indicates that activity in
this area will decrease after sunset, but there is an equal chance
that convection could continue into the overnight period.  Away from
convection, VFR conditions are expected with bases staying AOA 12kft
AGL. Near convection CIGs of 8kft to 10kft AGL will be seen.
&&

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

&&

UPDATE...Soulat
SHORT TERM...Nickerson
LONG TERM...Soulat
AVIATION...Planz

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