126
FXUS65 KVEF 200330
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
830 PM PDT Fri Jul 19 2024

.SYNOPSIS...Isolated to scattered thunderstorms expected again this
afternoon, with best chances in southern Nevada, the southern slopes
of the Sierra Nevada, and northwestern Arizona. Impacts will include
locally heavy rain, strong gusty winds, and small hail. Chances of
isolated thunderstorms return each day through the weekend before
increasing next week. Meanwhile, above average temperatures resulted
in an Excessive Heat Warning through the weekend, with temperatures
remaining elevated through the forecast period.
&&

.UPDATE...As the sun sets on another afternoon of monsoonal
convection, lingering shower and thunderstorm activity across the
area will continue to gradually diminish. The last few visible
satellite images prior to sunset show an impressive outflow boundary
moving south through Esmeralda and Central Nye Counties. 25 to 35
mph northerly wind gusts associated with the outflow have been
observed across the Nevada National Security Site. These winds will
continue to push south through southern Nye County and likely into
the Death Valley National Park area. Locally, we had our own wind
shift around 7:30 pm PDT as an outflow from storms in northeastern
Clark County rolled through the area. Slightly to the west of the
Las Vegas Valley, in the Red Rock area, storms dropped a quick 0.25
to 0.90 inches of rain earlier this afternoon. One gauge in the area
picked up a total of 0.89 inches of rain with 0.39 of that falling
in a 5-minute period, which prompted the issuance of a Flood
Advisory for the area. Chances for isolated showers and
thunderstorms will return each afternoon through the weekend, with
the highest chances for precipitation tomorrow afternoon in the
northern and eastern portions of our forecast area.

Afternoon convection capable of producing gusty outflow winds,
dangerous lightning, and periods of moderate-to-heavy rain won`t be
the only weather related threats to keep an eye out for over the
weekend, as the southern portions of our forecast area find
themselves in an Excessive Heat Warning. Temperatures will be around
8 to 10 degrees above normal, yielding Major to Extreme HeatRisk for
the valleys and lower elevations of the Mojave Desert.
&&

.DISCUSSION...Today through next Friday.

Moisture caught beneath an upper-level area of high pressure over
the region will return isolated shower and thunderstorm activity to
our forecast area each day through the weekend. Today will have the
most coverage over the next few days, with thunderstorm activity
expected along the southern Sierra crest, across southern Nevada,
and across northwestern Arizona. Ample moisture in Arizona could
result in locally heavy rain rates and flash flooding, whereas dry
low levels in southern Nevada could result in gusty outflow winds
over 40 mph. Storms will favor the higher terrain as it relies on
heat-driven instability and orographic lift.

Meanwhile, the center of the aforementioned high pressure will
remain over southern Nevada through the weekend, which will result
in both afternoon high temperatures and overnight low temperatures
ranging 8 to 10 degrees above seasonal averages. As such, an
Excessive Heat Warning is in effect for our southern zones today
including southern San Bernardino County, southern Mohave County,
and the Colorado River Valley... expanding to include southern
Nevada and portions of southeastern California Saturday... and
lasting through Sunday. Temperatures will remain elevated through
the forecast period with pockets of "Major" HeatRisk in desert
valleys. Will continue to assess temperatures coupled with
acclimation through the weekend to see if additional heat-related
headlines are warranted next week.

As mentioned in the previous forecast discussion, the monsoonal high
will shift slightly northwest next week, which will allow for
enhanced moisture advection up the Colorado River Valley once again.
As such, afternoon precipitation chances range from 20% to 40%
across southern Nevada and southeastern California (with upward of
60% chance around northwestern Arizona) each day through the week.
Continued the methodology from the previous shift of taking
precipitation chances down somewhat in the desert valleys, as NBM
climatology is likely artificially inflating chances in these areas.

Shortwave troughing originating from the Pacific Northwest will
squash our high pressure somewhat, which may provide some relief to
well-above-average temperatures.
&&


.AVIATION...For Harry Reid...Another round of showers and
thunderstorms expected around the Las Vegas Valley today, with
nearby storms picking up around 19Z and lasting through 03Z. Strong,
gusty winds possible from their direction with speeds to 30 kts.
Outside of thunderstorm activity, winds will favor the south-
southeast around 10 kts. Thunderstorms return Saturday afternoon
with similar timing, but with less coverage than today. Less than 10
percent chance of a thunderstorm over the terminal on Saturday.
Ceilings will drop to aoa 12kft with thunderstorm activity.

For the rest of southern Nevada, northwest Arizona and southeast
California...Thunderstorms in the vicinity of KLAS,
KVGT, KHND, KBIH, and KIFP expected to cause erratic, gusty winds at
terminals from the storm`s direction. Best timing of convection will
be between 19Z and 03Z with gust potential to 30 kts. Ceilings will
drop to 10-12 kft with thunderstorm activity. Winds will return to
diurnal trends overnight before thunderstorm chances return to the
region Saturday afternoon with similar timing, but less coverage.
&&


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


$$

UPDATE...Stessman
DISCUSSION/AVIATION...Soulat

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