Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 260249
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
749 PM PDT Sun Jun 25 2017

.SYNOPSIS...Conditions will finally begin to cool early this week
as a weather system moves across the western states. This system
will bring increased winds to much of the region, especially
Monday. Outside of a few isolated showers/storms this afternoon,
dry conditions are expected this week.
&&

.UPDATE...Most of the weak shower activity that did try to get
going in Lincoln and the Sierra on a downward trend as main
moisture axis continues to shift northeast, and drier/more subsident
air begins to push in. The main forecast concern for the rest if
the evening/tonight is if the boundary layer will decouple and
allow winds to become light and variable or if breezy southwest to
west winds will remain through the overnight.
&&

.PREV DISCUSSION... /issued at 150 PM PDT Sun Jun 25 2017/

.SHORT TERM...Today through Tuesday.

Weak shower activity has developed across the higher terrain of
Mohave county as expected this afternoon. Elsewhere, there have
also been some indications of virga over the NNSS and Lincoln
County while clouds have struggled to develop over the Sierra.
Expect most of this activity to fizzle after sunset today with the
loss of heating.

Focus then turns to a trough that will push across the western
states Monday and Tuesday which will bring increased winds to the
region. These winds are expected to peak on Monday, with isolated
gusts in the 35 MPH range across southern Nevada and northwest
Arizona and closer to 40 MPH across the deserts of southeast
California. See the FIRE WEATHER section for fire danger concerns.
This trough will also bring relief from the prolonged period of
excessive heat that we`ve been experiencing. The latest guidance
has cooled high temperatures yet again for Monday and as a result
I`ve dropped the high temperature forecast for Las Vegas to 108F.
It`s going to be a challenge to tie the record for consecutive
days at or above 110F of 10 days (1961). With a current
temperature of 110F as of this writing, we currently stand at 9
days. Winds are expected to decrease slightly both Tuesday and
Wednesday with temperatures cooling another 2-3 degrees each day.

.LONG TERM...Wednesday through Saturday.

By Wednesday, the ridge over the southwest will continue to be
suppressed a bit as the tail end of a trough drapes over much of the
western CONUS through the work week. Models are now indicating that
a impulse/shortwave will develop off the coast of northern
California by Friday. The strength and impacts of this feature are
uncertain at this time as model variance is high for Fri and Sat.

Temperatures will be approaching normals by Wed and remaining near
normal through the forecast period. Breezy southwest winds are
expected each afternoon with wind speeds 10 to 15 mph and gusts
around 20 to 25 mph. Wednesday afternoon, both the GFS and ECMWF are
showing a tight gradient over much of central Mohave County. This
will cause some gusty southwest winds up to 30 mph Wed afternoon.
Otherwise, dry and mostly clear conditions through the rest of the
work week and into the weekend.
&&

.FIRE WEATHER...Outside of a few isolated showers/storms today,
dry conditions are expected this week. Conditions will finally
begin to cool early this week as a weather system moves across the
western states. This system will bring increased winds to much of
the region, especially Monday. This prompted a Red Flag Warning
to be issued for Monday for portions of southern Nevada and
northwest Arizona. Winds do look borderline but with the hot
temperatures it`s fairly easy for gusts to mix to the surface so I
left the RFW in place. Another concern is winds across the Sierra
and San Bernardino Counties where gusts may approach 40 MPH at
times which could lead to periods of Red Flag conditions in those
areas.
&&

.HYDROLOGY...Observed flows on unregulated creeks, specifically
Independence Creek, Big Pine Creek and Rock Creek indicated flows
have decreased slightly since their peak flows occurred earlier this
week. Creeks, streams and rivers along the eastern Sierra slopes of
Inyo County as well as the Owens Valley will be flowing high and
fast through into at least early next week. Minor flooding could
occur near creeks as well as a few low water crossings on some
roadways. 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.
&&

.AVIATION...For McCarran...Light winds generally out of the east
will veer southwest  and increase this afternoon. Winds over 10kts
are anticipated by 23Z today. Expect gusty west-southwest winds to
continue through much of the night, with gusts over 20kts possible
after 03Z. There with a chance that winds will drop off for a brief
time between 10Z and 15Z and go light, however confidence is too low
at this time and did not include it in the current TAF forecast.
Gusty southwest winds will continue tomorrow, with stronger winds
anticipated after 18Z Monday than what we should see today.
Otherwise, virga concerns in the McCarran airspace will be minimal
through the afternoon, and VFR scattered clouds should move away by
tonight.

For the rest of southern Nevada, northwest Arizona and southeast
California...Winds will increase out of the west or southwest this
evening and overnight, with the strongest winds expected in San
Bernardino county on the downslope side of the Spring Mountains.
After a brief lull Monday morning, west winds will pick back up
Monday late morning, and will be stronger than today. Otherwise,
isolated showers or virga are possible in the higher terrain this
afternoon, but widespread ceiling/precip issues are not anticipated.
&&

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

$$

Update....................Steele
SHORT TERM/FIRE WEATHER...Wolcott
LONG TERM.................Kryston
AVIATION..................Allen
HYDROLOGY.................Pierce


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