Area Forecast Discussion
Issued by NWS Las Vegas, NV

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742
FXUS65 KVEF 151702
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
902 AM PST Sat Dec 15 2018

.SYNOPSIS...Fair weather conditions are expected across the
region today before another low pressure system increases rain
and mountain snow chances across the Sierra and southern Great
Basin. Along with precipitation chances, strong winds can be
expected in the Sierra Sunday night and Monday. After Monday, dry
and calm conditions are expected through the end of the week along
with above normal temperatures.
&&

.UPDATE...
A shortwave ridge will build in over the Great Basin today ahead of
a strengthening low in the Gulf of Alaska. Lingering cloud cover
remains along the I-40 corridor this morning but will continue to
shift eastward away from the area throughout the day leaving mostly
sunny skies. Temps will top out a few degrees higher than yesterday
with full sun and light winds except for the Bullhead City/Laughlin
area where persistent afternoon breezes continue.

&&
.SHORT TERM...today through Monday night.

Satellite imagery shows a deck of mid to high clouds slowly moving
across the region as well as a large, closed upper low rotating in
the Gulf of Alaska. The back edge of the cloud deck should move east
of Las Vegas shortly after daybreak allowing abundant sunshine
today. The aforementioned low will bring a chance of scattered
rain and high- elevation snow showers to the Sierra and southern
Great Basin Sunday night through Monday. In general, precip totals
are to be light as the main moisture axis is directed toward the
Bay area. With an elevated moist layer, a spread an thick layer of
across the region Monday.

Prior to the showers, strong winds are likely across the mid and
upper slopes of the east Sierra as the trough axis rotates into
California Sunday night into early Monday morning. With uncertainty
in how quickly the trough axis moves inland and orientation of
upper jet, confidence in wind gust speeds and reach of downslope
winds is low; however, winds between 30-40 MPH are possible in
lower slopes and Owens Valley and 45-65 MPH between the crest and
the middle- slopes. If models continue to show favorable downslope
conditions aligning, wind headlines will likely be needed. Aside
from the Sierra, a breezy belt of prefrontal southwest winds are
likely across the western Mojave Desert and across far southern
Nevada, with lighter winds expected across remaining areas.

Temperatures will read about 4-6 degrees above normal through the
weekend. Even with mostly cloudy skies, increased winds on Monday
should keep temperatures above normal for mid December.


.LONG TERM...Tuesday through Friday.

The trough will exit to the east on Tuesday, bringing dry and quiet
weather to the area through the rest of the week. On Tuesday,
lingered clouds compared to the previous forecast as high level
moisture looks entrenched over the area through the afternoon. Still
think there will be sun but it could be filtered by high clouds
streaming in on north to northwest flow.

Strong ridging building into the southwest US through Friday. A
surge of warmer air is expected with this ridge. Model guidance has
trended warmer for the second half of the week, so bumped up
temperatures a degree or two from the previous forecast. It will
depend on the timing of high clouds streaming in at times through
the end of the week though, so temperature forecast could fluctuate
with later updates. High confidence either way in well above normal
temperatures Wednesday-Friday.

Long range models do show a weak Pacific trough for Friday or
Saturday, but not enough confidence to add details or change the
forecast for  that time period at this time.
&&


.AVIATION...For McCarran...Winds will remain light at 8 knots or
less for the period and follow along diurnal trends. As winds go
near calm, variability in direction is likely. Clearing clouds are
expected by mid morning, but then high clouds should move back in
late Saturday afternoon and evening. Dry weather will continue into
Sunday.

.For the rest of southern Nevada, northwest Arizona and southeast
California...Winds will remain light at 10 knots or less for the
period and follow near to diurnal trends. The exception will be near
Bullhead City/Laughlin where north winds continue to maintain speeds
between 10-15 knots today through tonight.  Scattered high VFR
clouds will persist.
&&


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

$$

SHORT TERM...........Boothe
LONG TERM/AVIATION...Wolf
UPDATE...Guillet

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