Damaging Wind in Nevada, August 29, 2020

Area Forecast Discussion
National Weather Service Las Vegas NV
810 PM PDT Fri Aug 28 2020

.SYNOPSIS...
Increasing chances for storms can be expected for the weekend as
moisture filters in from the south across Mohave, eastern Clark,
and eastern San Bernardino counties. Strong storms which could
produce flash flooding and gusty winds will be possible. A Flash
Flood Watch has been issued for central and southern Mohave County
where more widespread flooding is expected.

&&

.UPDATE...Another tranquil evening across the region but changes are
on the horizon. A surge of moisture will work up the Gulf of
California tomorrow with shower and thunderstorm chances returning
to parts of the Colorado River Valley and Northwest Arizona. Already
seeing some mid level moisture getting entrained into the flow with
this afternoons 00z VEF sounding showing a small moist layer near
600mb. Current HRRR guidance seems a bit bullish developing some
late night shower activity out of this pocket of mid level moisture
but some virga activity may pop in the early morning hours mainly
south and east of Las Vegas.  Made some small tweaks to the cloud
cover grids tonight but otherwise no major changes needed.

-Outler-

&&

.SHORT TERM...Currently, a pattern is unfolding that is supportive
of flash flood potential for areas where storms develop on
Saturday. High pressure located to our east will slowly sink
southward toward northern Mexico as low pressure continues to
spin near the central CA coast and larger trough moves into the
PacNW. In between these two features a weak jet will set up
across northwest AZ and southern NV. Add in a gulf moisture surge
fortified by Tropical Depression Hernan near the tip of Baja and
we have a portion of our area with a favorable set up for storms
capable of producing flash flooding as well as strong winds.
PWATs will increase northward going into Saturday with the 1.00 in
PWAT line cutting through central Clark into central San
Bernardino County and across the AZ Strip. The moisture gradient
will be quite tight just to the north of this boundary as PWATs
drop to around 0.5 inches across the southern Great Basin and Inyo
County. The jet will provide upper level support and a decent
amount of wind shear to work with on Saturday along with 1000-1500
J/kg CAPE values which could support some organized complexes of
storms. Best chances for storms remain across Mohave County where
we have decided to go with a Flash Flood Watch for central and
southern portions of the county. This is where moisture, forcing,
and instability will all be in place for higher coverage of flash
flood producing storms. However, strong storms producing
localized flash flooding will be possible outside of this area as
well. With upper level support and little change in available
instability, activity could continue through early Sunday morning
across Mohave County.

Storm chances will continue on Sunday but will be dependent on
what transpires tomorrow and tomorrow night. If it looks like
another active day is in store, the Flash Watch Flood may need to
be extended or expanded. As moisture increases this weekend temps
will moderate as a result, dropping a few degrees from today's
high temps.

.LONG TERM...Monday through Friday.

On Monday, a mid-level trough will dive down from the PacNW
through the Great Basin to the southern Plains. Not much wind to
speak of with its passage but it will push moisture southward out
of the area and storm chances will be limited to the furthest
southeast corner of our area of responsibility Monday and Tuesday.
Temps will continue on a downward trend, bottoming out on Monday
with high temps right around seasonal normals which means around
100 degrees for Vegas. A strong ridge builds in behind this
trough and temps will rebound for the second half of the work
week with dry conditions.

&&

.AVIATION...For McCarran...Winds will shift from south to
southwest this afternoon at speeds of 10-15 knots gusting near 20
knots. South to southwest winds will continue overnight at 8-10
knots before becoming breezy out of the south to southwest once
again on Saturday afternoon. Storms will be possible to the east
across Mohave County and the Colorado River valley with best
chances for any outflows in the valley after 00z Sunday.

For the rest of southern Nevada, northwest Arizona and southeast
California...Breezy, southwest winds will continue through this
evening with gusts of 20-25 knots possible. This wind pattern
will again be present on Saturday. Storms will develop Saturday
afternoon with highest chances across Mohave County and lower
chances over the Colorado River Valley and the eastern half of San
Bernardino County. There are low chances for storms to directly
affect any of the terminals but outflow are possible at all
terminals less KBIH. Storms could potentially last through early
Sunday morning for Mohave County.

&&

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

SHORT TERM/LONG TERM...Guillet
AVIATION...Guillet

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