Dust Storm Warning 4, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
153 PM PDT Sat Jul 14 2018

.SYNOPSIS...Scattered thunderstorms are expected to persist
through the rest of the afternoon across the southern Great Basin,
northwest Arizona and the south Sierra. There will be a
possibility of thunderstorms moving into Clark County later this
evening. Storms may produce localized flash flooding and sudden,
gusty winds. Thunderstorm chances will trend downward Sunday and
Monday as high pressure builds over the region. Temps will
increase a few degrees each day through Tuesday.
&&

.SHORT TERM...Tonight through Monday.

Near Term (this afternoon/evening)...Scattered, generally low-end
and short-lived, convection has blossomed across most of the
forecast area. With the entire area destabilized - except San
Bernardino County - and MLCAPE between 1000-2000 J/kg, convection is
going to persist through at least sunset, mainly over the higher
terrain. Steering flow continues to be slow, under 5 mph, so flash
flooding will be the primary threat through the afternoon along with
lightning and sub-severe outflow winds. For this evening confidence
is low on how exactly convection will materialize. Convective
Allowing Models are indicating a complex of storms developing across
Nye and Lincoln counties and pushing southward toward Clark (Las
Vegas), Mohave, and eastern San Bernardino. While the models have
been overly aggressive with outflow-dominant convection so far this
monsoon season, there is already clusters of thunderstorms across
the NNSS and southern Lincoln County. With southeasterly mean flow
and individual storm motion vectors also southeasterly, there is a
possibility that storms across the aforementioned areas may persist
and move southward this evening. If this materializes, 40-50 mph
outflow wind gusts, heavy downpours, and localized flooding would be
the primary impacts for Las Vegas and areas to the south. Another
scenario thats possible, which would be similar to last Monday's
event, is converging outflows from convection across Mohave and
Lincoln Counties. Last scenario is that convection may dissipate all
together with the loss of diurnal heating.

Sunday/Monday...Overall, a downward trend in convective coverage is
expected Sunday and Monday. This will occur due to a ridge of high
pressure stretching from the eastern Pacific across the Great Basin.
Under this ridge temperatures are expected to rise quite a bit -
about 3-4 degrees each day. With the heat, isolated convection over
the terrain is expected and primary threat will be sub-severe
outflow winds and localized flooding with strong storms.

.LONG TERM...Tuesday through Saturday.

An easterly wave is expected to move into the area by TUE-WED which
should increase thunderstorm activity. Most notably with this
feature is the increase in bulk shear to the area WED with some
areas seeing an excess of 30 kts, based on the current GFS. With an
increase in shear the primary threat would be strong outflows
capable of producing strong to severe winds. Best chances for
thunderstorm activity will mainly be areas south of I-15 TUE, with
better chances of seeing more widespread activity WED. As the wave
moves west WED the high pressure shifts eastward over New Mexico and
west Texas. The eastward placement of the high should result in some
dry air off the SoCal coast to filter in across western portions of
our CWA by late week. Beyond THU, models differ drastically in the
placement of the high and thus confidence is low on whether the dry
air will stick around for the weekend or not.

Besides storm chances, expect light winds less than 10 mph,
temperatures near normal for mid July and partly sunny to partly
cloudy skies.
&&

.AVIATION...For McCarran...Expect winds under 10 knots through
tonight, unless thunderstorm outflows affect the terminal. It
appears the best chance for that to happen would be around or after
sunset, when there is a chance of outflows coming from either the
north or east or both. Similar conditions are expected Sunday.

For the rest of southern Nevada, northwest Arizona and southeast
California...Expect scattered thunderstorms this afternoon and
evening, with the fewest storms over San Bernardino County. The main
threats with storms will be heavy rain, mountain obscuration, and
erratic gusty winds. Similar conditions are expected Sunday, with
slightly less thunderstorm coverage than today.
&&

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

SHORT TERM...Boothe
LONG TERM....Kryston
AVIATION.....Morgan

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