Flash Flood Warning 51, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
1218 PM PDT Sun Aug 11 2024

.SYNOPSIS...Monsoonal moisture creates an environment that will
result in additional rounds of thunderstorms today and tomorrow,
mainly in the afternoon and evening. Storms may bring gusty winds
and heavy downpours. A change in the weather pattern on Tuesday
brings drier air which will limit precipitation potential and
bring down temperatures closer to normal for this time of year.

&&

.SHORT TERM...Tonight through Monday.

A ridge of high pressure is in place over the southwestern United
States while an inverted trough sits over the Baja Peninsula. This
setup continues to draw monsoonal moisture into the region with
PWATs in the 1 to 1.8 inch range over Clark, Lincoln, Mohave, and
San Bernardino Counties. Between ample moisture and 1000 - 2000
J/kg SBCAPE to work with, thunderstorm activity should pick up
through the afternoon and last into the evening for this area,
especially in northern Mohave County. Lingering storm develop may
also occur overnight as outflow boundaries collide and create lift
for new storms. Overall activity should be limited in areas to
the northwest and west of the forecast area as moisture and
instability decrease. The main threat with any storms that form is
heavy rainfall due to a combination of ample moisture and slow
storm movement. Flash flooding may occur under the strongest
storms and areas with continuous storm coverage. As seen with
yesterday's storms, localized gusty outflow winds and frequent
lightning may also occur. A similar setup tomorrow should yield
similar results, though coverage may start to be limited in the
evening as a trough directs southwesterly flow into the region and
drier air takes over. Outside of storms, breezy southerly winds
are expected today and tomorrow due to a north-south pressure
gradient created by the inverted trough.

.LONG TERM...Tuesday through Saturday.

Increasing southwesterly flow aloft will bring a drying and cooling
trend to the region as troughing develops across the West. This will
mark another extended break period from the monsoon, with moisture
becoming confined to Northwest Arizona. In fact, by Wednesday and
Thursday, even most of Northwest Arizona will likely be mostly dry.
Meanwhile, temperatures will respond with a gradual cooling trend,
falling closer to mid-August normals and complimented by
southwesterly afternoon breezes.

Forecast confidence decreases Friday onward as some ensemble members
suggest the western US trough shifting westward and allowing the
monsoon high to build back towards the Four Corners. This would
allow for a more southerly flow pattern and potentially draw some
monsoonal moisture back into our eastern zones. Alternatively, other
guidance maintains a general troughing pattern over the region and
keeps dry air locked into the area. Ensemble members are roughly
split on the two options, so for now a modest increase in storm
chances return to mainly northwest Arizona Friday and Saturday, with
temperatures remaining near seasonal normals.

&&

.AVIATION...For Harry Reid...Thunderstorms over the local mountains
are likely again this afternoon and evening, with the primary
concern being outflow boundaries which could disrupt the winds at
the airfield. There is a lower (25%) chance of a storm directly
affecting the terminal. Storms should dissipate shortly after
sunset. For Monday, expect storms to remain generally east of a line
from Primm to Boulder City, with less coverage overall, 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. Drier air moving in from the west
on Monday will limit thunderstorm chances to areas along and
southeast of Interstate 15, with less coverage expected than
today.

&&

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

&&

SHORT TERM...Meltzer
LONG TERM...Outler
AVIATION...Morgan

For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter

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