Flash Flood Watch 7, NWS Las Vegas, NV

Area Forecast Discussion
National Weather Service Las Vegas NV
200 AM PDT Sat Oct 13 2018

.SYNOPSIS...Showers and thunderstorms will skirt our southern areas
today as a low pressure system moves across the region. This will be
followed by a strong cold front Sunday bringing gusty north winds,
and the first freeze of the season to parts of the Owens Valley and
southern Great Basin Monday morning. Gradually moderating
temperatures and dry conditions are expected most of next week.

&&

.SHORT TERM...through Monday morning.

Closed low currently located just offshore the San Diego coastline
will continue to spark shower and thunderstorm activity across much
of Southern California and parts of the western Mojave Desert
through the morning hours. Expect this activity to translate
eastward in the coming hours, with the bulk of the precipitation
staying along and south of I-40, but some lighter showers may creep
as far north as the southern tip of Nevada by sunrise. Further
south, more robust activity aided by strong divergence aloft within
the northeast quadrant of the closed low will be capable of locally
heavy rain and isolated flash flooding, as was noted earlier this
evening near Joshua Tree. Timing-wise, these thunderstorms will
likely reach the Lake Havasu area before sunrise, and into the
southern half of Mohave county shortly after.  Heaviest
precipitation will likely exit to our east by midday, but some
residual wrap around precipitation may impact Mohave county and
parts of the Mojave Preserve through the early evening hours before
dissipating as the low pushes eastward.

By Sunday, a potent northern stream trough will dive southward out
of the central and northern Rockies and pinch off over central
Arizona by Monday afternoon.  This feature will drag a fairly strong
cold front southward with it, with gusty north winds filling in,
especially along and near the Colorado River valley.  It will also
usher in some of the coolest air we've seen so far this fall, with
the first freeze of the season likely near Bishop and northern Owens
Valley, as well as most of the southern Great Basin.  With fairly
high confidence and model agreement on these temperatures, I went
ahead and upgraded the freeze watch to a warning for those areas.

.LONG TERM...Tuesday through Friday.

A closed low meanders over the southwest much of next week keeping
temperatures below normal. Kept the period dry, however there is
more uncertainty today as models flipped back shifting the closed
low further westward Wednesday/Thursday. If the westward shift
occurs there could be just enough instability under the cool pool
aloft to generate some precipitation over Mohave County.  &&

.AVIATION...For McCarran...Generally light and diurnal winds are
expected today with dry conditions expected. FEW-SCT clouds can be
expected with bases of 9-12k, with decreasing clouds after sunset.
Gusty north winds will move in late Saturday night, with gusts to 20
knots possible.

For the rest of southern Nevada, northwest Arizona and southeast
California...Numerous showers and thunderstorms are likely early
this morning lasting into midday, primarily south of a KDAG-KIGM
line. In this area, CIGs may drop below 3k at times, and periods of
heavy rain and lightning will be possible. Improving conditions are
expected further north, with skies quickly becoming bkn-sct with
northward extent and decreasing shower activity. Generally light and
diurnal winds are expected for the TAF sites today, though gusty
north winds will begin impacting KBIH by early this evening with
gusts to 25 knots possible.

&&

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

SHORT TERM/AVIATION...Outler
LONG TERM...Pierce

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