Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 252055
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
155 PM PDT Tue Jul 25 2017

.SYNOPSIS...Scattered showers and thunderstorms will continue across
the area into the early evening. Any storms will be capable of
producing flash flooding. Gradually drying conditions are expected
Wednesday through Friday with temperatures warming back to above
normal. Another uptick in moisture is expected this weekend into
early next week.
&&

.MESOSCALE DISCUSSION...Heavy precipitation continues across central
Mohave and eastern San Bernardino. Numerous Flash Flood warnings are
in effect for this area where rainfall amounts of around 2 inches
per hour are likely. Significant area of upper level divergence
remains in place of much of Mohave County to help maintain ongoing
convection.

Elsewhere...convection has begun to break out across
parts of Inyo, Esmeralda and Nye Counties, which will pose an
increasing flood threat during the afternoon and early evening.
There is sufficient shear in place across Inyo, Esmeralda, and Nye
Counties and along with the greatest instability, about 2000 J/kg of
CAPE, to increase the threat of stronger, potentially severe cells
in those areas through this evening.
&&

.SHORT TERM...Today through Wednesday Night.

Upper low along the northern California coast will gradually usher
in some drier air into the region over the next couple of days, but
in the meantime we have an abundance of moisture in place,
especially across eastern San Bernardino, Clark, Lincoln and Mohave
Counties. This combined with upper level support has produced a
widespread area of heavy rain with embedded thunderstorms across
portions Clark, eastern San Bernardino and across much of Mohave
County early this morning and into the early afternoon hours.
Rainfall rates have been 1 to 3 inches with many of these storms and
flash floods have occurred closing a number of roadways including at
Cottonwood Cove, Willow Beach and Temple Bar in the Lake Mead
National Recreation Area to name a few. The heaviest rain in
expected across the southern half of Mohave County and eastern San
Bernardino County into the early evening. As the upper low moves
further onshore on Wednesday the shower and thunderstorm activity
will be diminished with the greatest chance across the higher terrain
of southern Nevada and northern Mohave County. The upper low lifts
to the northeast ushering much drier air into southern Nevada and
southeast California on Wednesday night.
&&

.LONG TERM...Thursday through Monday

Much quieter weather is expected for the end of the week into the
weekend as high pressure works is way back over the area. A
significant upper level ridge sets up over us, with increasing model
agreement with the high being centered further west and that it will
dry out for a few days. Decreased precip chances for Thursday
afternoon from previous forecast. Heights will be increasing and
with limited moisture, think precipitation activity will be
isolated.

Generally dry weather will continue on Friday before chances for
precipitation return to the forecast. Models are not in an kind of
agreement on the next push of moisture and how that will translate
to shower and thunderstorm development. Some of the models bring in
higher PWATs and theta-e values by Saturday afternoon, while others
hold off until Sunday night. Favored the slower/drier solutions
since models tend to bring in moisture too quickly. This would
introduce showers and storm chances to Mohave County Saturday
evening...and brings chance precipitation to the entire area by
Sunday afternoon. Didnt make much in the way of chances after 18Z
Sunday as confidence is too low, with general chance for precip
across the entire area each day. Without a key feature to focus on
for lift, it will be hard to determine where things will get active.

The other thing to watch will be temperatures. Set up Friday and
Saturday (and maybe Sunday depending on how quickly moisture returns
to the region) is favorable for warmer than normal temperatures. 850-
700mb temperatures jump into the 30s on many of the longer term
models- up from the middle 20s off this evening`s sounding. A lot
will depend on how quickly moisture and precip returns, which will
make or break temps. Current model guidance isn`t too impressive
with high temperatures this weekend, and it will not be anything
similar to the heatwave we saw in June, but anyone with outdoor
plans Friday through Sunday should be prepared for the heat as
above normal temperatures look likely. Temperatures will cool off
with the wave of moisture pushing into the region.
&&

.FIRE WEATHER...Scattered showers and thunderstorms will occur over
much of the region into the early evening with most storms capable
of producing very heavy rainfall. Conditions will gradually dry out
later this week, with thunderstorms decreasing in coverage each day.
Temperatures will below normal through Wednesday, before returning
to slightly above normal late in the week. Another uptick in monsoon
moisture is expected to arrive sometime this weekend.
&&

.HYDROLOGY...Creeks, streams and rivers in northern Inyo County
have shown decreasing flows over the last couple of days.
However, some road closures continue in the area. Bishop Creek
Bypass and Big Pine Creek Bypass continue to be utilized to
minimize flows through Bishop and Big Pine. Remember, never drive
through flooded roadways or around barricades. Also, pastureland
or farmland adjacent to creeks, streams or rivers could experience
areas of standing water.

A flood advisory is in effect along the Muddy River with minor
flooding possible downstream into Overton, Moapa Valley and
Logandale for the rest of the afternoon.
&&

.AVIATION...For McCarran...Low confidence forecast for this evening
as shower and thunderstorm activity continues across portions of
Clark County, but at this point only mentioning showers in the
vicinity of McCarran into the early evening hours. Outflow
boundaries may impact winds at the terminal and the potential for
valley storms, but at this point will keep them out of the TAF.
Drier conditions are expected on Wednesday with a chance of
thunderstorm primarily over the higher terrain.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered showers and thunderstorms into the early
evening with the most coverage over Mohave County and eastern San
Bernardino County. Thunderstorm coverage will be less on Wednesday
with the best opportunities over the higher terrain of southern
Nevada and especially Lincoln County.

.SPOTTER INFORMATION STATEMENT...Thunderstorms capable of flash
flooding are possible once again today. Spotters are encouraged to
report any significant weather or impacts according to standard
operating procedures.
&&

$$

MESOSCALE/SHORT TERM/AVIATION/FIRE WEATHER...Czyzyk
LONG TERM........Allen


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