255
FXUS65 KVEF 110402
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
910 PM PDT Sat Aug 10 2024

.SYNOPSIS...Monsoonal moisture will continue to provide fuel
for thunderstorms across southern Nevada, northwest Arizona and
eastern San Bernardino County through Sunday. Above normal
temperatures will continue as high pressure persists over the
southwestern states. Drier air is forecast to push into the region
Monday and much of the coming week, reducing thunderstorm chances
and bringing slightly cooler temperatures to the region.
&&

.UPDATE...After an afternoon of mainly weak-pulse convection, an
outflow boundary moving north out of La Paz County, Arizona
triggered fairly robust storm development across Mohave County that
is gradually waning at this hour.  Some of the stronger cores
developing in the Hualapai Mountains and near Yucca suggested hail
up to quarter size and strong wind gusts. A few rain gages in the
Haulapais also observed some impressive rainfall totals, with one
guage east of the Pine Lake Community picking up 3.98 inches of
rainfall for the day. With the loss of daytime heating, convection
will continue to weaken through the remainder of the evening, though
a few lingering storms may pop up along boundary interactions across
Mohave County.

The current forecast is in good shape for the evening and no update
is necessary.

-Outler-

&&

.SHORT TERM...through Sunday night.

Thunderstorms started developing before noon over the mountains of
southern Nevada and northwest Arizona and conditions are favorable
for thunderstorm coverage to expand through the afternoon as cells
slowly move toward the east-southeast. This will increase the
potential for storms moving off the mountains and across the valleys
of central and southern Clark County including Las Vegas...
especially over the southern and western parts of the metro area.
Surface CAPE values around 1000 J/kg were in place across much of
southeast Nevada northwest Arizona and eastern San Bernardino County
in California and full surface heating will largely remove any
remaining CIN. Also, surface dewpoints in the upper 50s and
precipitable water values near 1.4 inches support the potential for
isolated heavy rain with some storms. After surface heating
initiates storms, boundary interactions should aid convection into
this evening especially over Mohave County and the lower Colorado
River Valley. Hi res models indicate the potential for convection
over southwest Arizona this afternoon to push widespread outflow and
additional low level moisture up across northwest Arizona and far
southern Nevada tonight.

This additional infusion of moisture will keep the moist and
unstable air mass largely over the same portion of our forecast area
Sunday. The latest HREF and NBM indicate a slight decrease in PoPs
over Clark County Sunday afternoon, but higher values over northeast
Mohave County around Colorado City. There are indications of
ingredients coming together for heavy rainfall concentrating around
that area Sunday afternoon.

High temperatures will continue to run 3-6 degrees above normal
which translates to highs of 103 to 109 across the Mojave
Desert zones. Overnight lows stay warm in the lower deserts.

.LONG TERM...Monday through Saturday.

A drying trend is shaping up Monday through at least Thursday as a
broad trough dropping down from the Pacific Northwest into the
western states leads to a widespread dry southwest flow which will
begin pushing moisture east of our area Monday then will likely
totally scour it out by Tuesday. An eastern Pacific high approaching
the SoCal coast then reinforces the drying with west-northwest flow
aloft Wednesday-Thursday which may persist beyond as ensemble
clusters indicate another broad trough dipping over the Pacific
Northwest and northern California/Nevada.

However, if this trough axis holds near the West Coast it would
allow the ridge to amplify over New Mexico/Colorado and resulting in
a southeast flow directing moisture from northern Mexico up across
Arizona and back into our area Friday and Saturday. The ECMWF
ensemble members are indicating this trend more than the GEFS. The
latest NBM Pop grids do bring 20-30 percent values into eastern
Mohave County Friday then spread 15-20 percent values into southern
Nevada by Saturday afternoon.

While we wait for monsoon moisture to return, breezy afternoons and
high temperatures holding generally between 100 and 108 degrees can
be expected for most desert zones.

&&

.AVIATION...For Harry Reid...A messy afternoon and early evening is
likely. Thunderstorms will develop over the local mountains and
drift east to southeast, ejecting outflow winds which will not only
impact airport operations but also help develop new thunderstorms.
There is a high (70%) probability of outflow winds of 20 to 30 knots
affecting the terminal, and a lower (30%) probability of a
thunderstorm directly impacting the airfield. By about 03Z the
weather should be settling down, but there is low confidence in what
the winds will look like at that time after possibly multiple rounds
of outflows. It looks like thunderstorm potential will be a little
bit lower on Sunday and much lower on Monday, although the Mormon
Mesa and Peach Springs corridors will still be affected.

For the rest of southern Nevada, northwest Arizona and southeast
California...Thunderstorm chances are expected this afternoon and
evening near and east of a line from Morongo Valley to Mount
Charleston to Rachel, with the highest chances in Mohave County. The
main threats will be erratic, gusty winds and locally lowered
ceilings with terrain obscuration. The same areas will be at risk
for thunderstorms Sunday, with the same threats, before drier air
moving in from the west pushes thunderstorm chances eastward to
Mohave County and the Nevada/Utah border area on Monday.
&&

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

$$

SHORT TERM/LONG TERM...Adair
AVIATION...Morgan

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