Flash Flood Warning 138, NWS Las Vegas, NV

619 
WGUS75 KVEF 030354
FFSVEF

Flash Flood Statement
National Weather Service Las Vegas NV
854 PM PDT TUE OCT 2 2018

CAC027-030404-
/O.CAN.KVEF.FF.W.0138.000000T0000Z-181003T0515Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Inyo CA-
854 PM PDT TUE OCT 2 2018

...THE FLASH FLOOD WARNING FOR SOUTHEASTERN INYO COUNTY IS
CANCELLED...

The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed any remaining road closures.

LAT...LON 3637 11637 3632 11630 3579 11606 3580 11677
      3625 11693

$$

Boothe

Area Forecast Discussion
National Weather Service Las Vegas NV
250 PM PDT Tue Oct 2 2018

.SYNOPSIS...Abundant moisture remains in place today with scattered,
locally heavy downpours possible across much of the region. A
pacific storm system will approach tomorrow, bringing the potential
for strong thunderstorm development Wednesday afternoon and evening
to Southern Nevada and Northwest Arizona.  A series of additional
weak storm systems will keep conditions cool and unsettled into
early next week.

&&

.SHORT TERM...through Thursday night.

A highly unusual airmass has invaded the forecast area, largely
thanks to the remnants of Rosa moving into the Sonoran Desert, and
additional northward moisture advection ahead of a Pacific closed
low offshore.  Precipitable water values are generally at or above
1" north of I-15, while climbing to 1.5-1.75" further south. This
has led to a highly efficient airmass for heavy rainfall, despite
the overall lack of forcing. Widespread rainfall of 1/2 to 3/4" was
observed across southern Mohave county this morning, and lingering
showers continue to push north into Utah. Meanwhile, scattered
showers across southern Nevada and eastern California have
occasionally been observed to have rainfall rates over an inch per
hour, despite the small and shallow nature of the cells. Additional
thunderstorm activity has been observed in the Owens Valley and
Esmeralda county, as a potent jet aims at the south Sierra ahead of
the Pacific closed low.

Looking ahead, suspect activity will largely diminish with daytime
heating tonight, and I plan to drop the Flash Flood Watch with the
afternoon package as coverage of heavy rain looks isolated at best.
However, thunderstorm chances will return tomorrow as a powerful
closed low moves ashore, and a strong (100+ knots at 300 mb) jet
aims for Southern Nevada and Northwest Arizona.  This low will work
to cool temperatures aloft, while abundant low level moisture remains
in place, and will also encourage widespread lift across the area.
In addition, 40-50 knots of bulk shear will certainly favor the
potential for strong and severe thunderstorms.  The Storm Prediction
Center does have our region highlighted in a Slight risk for severe
weather, which is quite unusual, but seems reasonable given the set
up.  Best window for strong storms looks to be in the evening as the
energy pushes into the Mojave Desert, and the strong jet traverses
eastward through the region.  Localized flash flooding will again be
a concern, a following shifts will want to evaluate that risk as
updated model data becomes available.

The closed low will open into a wave and push eastward late
Wednesday night into Thursday. Drier air will filter in behind with
only a few residual showers hanging out across the southern Great
Basin. Temperatures will remain several degrees below seasonal
normals.

.LONG TERM...Friday through Tuesday.

A strong cooling trend and unsettled weather is in store for the
coming weekend. Energy diving out of the Gulf of Alaska will reach
Nevada late Friday and begin to carve out a deep broad closed low
over the western states Saturday and Sunday...with the center
roughly over Utah by Sunday. This will produce a strong northwest
flow over our region with gusty winds at times. Limited moisture
with the cold pool over southern Nevada and northwest Arizona will
result in isolated to scattered showers and snow levels dipping to
around 6500 to 7000 feet over south central Nevada by Sunday. After
a long period of above normal temperatures, we will finally see
readings drop well below normal Saturday through Tuesday with highs
in the mid 70s to lower 80s across most of the Mojave Desert region.

&&

.AVIATION...For McCarran...Clouds will decrease this evening
with generally scattered coverage overnight through Wednesday
morning with bases 8-12 kft. Light south winds will develop by early
this evening and will persist into Wednesday. There will be the
potential for thunderstorms to develop over southern Nevada late
Wednesday afternoon and evening that will likely impact the Mormon
Mesa and Peach Springs corridors along with a slight possibility of
impacting the KLAS terminal area.

For the rest of southern Nevada, northwest Arizona and southeast
California...MVFR conditions will persist across northwest Arizona
this evening along with scattered showers and mountain obscuration
then gradually improving conditions will develop late tonight
through Wednesday morning. The rest of the region will see isolated
showers diminishing after sunset with scattered to broken clouds
generally 8-12 kft MSL. Isolated thunderstorms from the southern
Sierra across west central Nevada will dissipate after sunset. The
threat of squall lines with scattered strong to severe thunderstorms
will increase Wednesday afternoon and evening across the region as a
low pressure system moves inland from the California Coast.

&&

.SPOTTER INFORMATION STATEMENT...Isolated flash flooding as well as
a few severe thunderstorms will be possible through Wednesday
evening. We encourage spotters to report any significant weather or
impacts in your area.

&&

SHORT TERM...Outler
LONG TERM/AVIATION...Adair

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