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fxus65 kvef 222218 
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Area forecast discussion
National Weather Service Las Vegas Nevada
318 PM PDT sun Sep 22 2019

Synopsis...the next trough of low pressure will begin to work its
way into the region late today and Monday providing an increase in
southwest winds in Inyo and western San Bernardino counties this
afternoon. Showers and thunderstorms are possible across far
southern Nevada, the Colorado River valley and much of northwest
Arizona on Monday. A prolonged period of windy conditions with a
cooling trend develops going into next weekend.
&&

Discussion...through Saturday.

Weather concerns through the period center around upper-level low
pressure dropping into the region and combining with a surge of
subtropical moisture through Tuesday. Main impacts will be
thunderstorms with gusty winds, heavy rain, and hail all possible.

Upper-level trough of interest current onshore around the or/California
border. This feature will continue digging southeast and close off
overhead by tomorrow afternoon. At the same time poleward
transport of moisture from Lorena remnants will bring pwats of
0.75-1.25 inches up through Mohave County. As daytime heating
increasing instability across Mohave County during the day,
isolated to scattered thunderstorms are likely to start
developing. Given ample shear, these storms will be capable of
organization, producing strong winds, hail, and even heavy rain.
The flooding threat should be limited for most of the day by storm
motions of 20 kts or more.

As the day wears on into the evening and overnight, things
continue getting interesting. While moisture and instability
decrease somewhat, height falls, steeper mid and upper-level lapse
rates, and strong forcing for ascent will likely keep activity
going - while also reducing storm motion. This will result in
continued storms into midnight for much of Mohave County, with the
greatest flooding threat from about 5pm - midnight. Hard to also
rule out a stray shower/storm or two underneath the low from Las
Vegas to Tonopah tomorrow afternoon and evening either. For now,
have limited pops in these areas, but could probably use another
bump up in future forecasts.

The upper-level low will slowly sink to the south Tuesday onwards,
with weakening forcing and limited moisture resulting in
decreasing pops. Generally quiet weather is then expected before
another potent trough bringing gusty winds and even cooler
temperatures by the weekend. &&

Aviation...for McCarran...light and variable winds under
6-7 knots are expected through the afternoon, favoring an easterly
wind direction. Winds will shift to the southeast then to the south-
southwest through the early evening and will continue through the
overnight period. Slightly stronger southwest winds are expected
tomorrow by 18z, with sustained winds 10-12 knots and gusts to 20
knots. Storms will be possible mainly east of the Las Vegas Valley
tomorrow evening. Low confidence, but a few scattered showers will
be possible in or around the valley tomorrow as a potent low
pressure system moves through southern Nevada. Scattered to broken aoa 25 kft
expected through tomorrow morning, then scattered to broken aoa 15 kft
tomorrow afternoon.

For the rest of southern Nevada, northwest Arizona and southeast
California...light and variable winds expected to continue through
the afternoon with southerly winds developing later this afternoon
across most taf sites. Slightly stronger southerly winds will
develop late tomorrow morning with gusts to 15-20 knots before a
cold front moves through bringing northwest winds of 10-12 knots
across much of the region by tomorrow afternoon. Scattered to broken aoa 25
kft expected through tomorrow.
&&

Spotter information statement...spotters are encouraged to report
any significant weather or impacts according to Standard operating
procedures.
&&

$$

Discussion...Steele

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