Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 181549 AAA

Area Forecast Discussion
National Weather Service Las Vegas NV
848 AM PDT Sun Mar 18 2018

.SYNOPSIS...Morning showers will taper off over Northwest Arizona
with calm but cool conditions expected elsewhere. Periods of mid and
high clouds can be expected the next few days with slowly moderating
temperatures. A weather system will approach midweek bringing a good
chance of widespread rain and very high mountain snow to the region,
especially north of I-40.

.UPDATE...Updated to decrease POPs and clouds in northern Mohave

Storm system pulling off to the east this morning. Clouds clearing
out of northern Mohave County revealing snowfield from the higher
plateaus surrounding the Colorado River in central Mohave County
northeast to Colorado City/Pipe Spring Natl Monument. Additional
snowfields noted across central/northeast Lincoln County and higher
terrain of central Nye County. Otherwise, temperatures will stay on
the cool side with reading about 10 degrees below normal. Also, area
will see some increasing high clouds from the west late this
afternoon and overnight.

.SHORT TERM...through Monday night.

Widespread rain and snow above the ~4000 foot level persist early
this morning across mainly the northern half of Mohave county.
Precipitation amounts based on the Mohave County flood control
gauges are generally between a tenth and a quarter inch of liquid,
with localized spots over a third of an inch. Colorado City has been
reporting moderate to heavy snow at times overnight as well, though
we have not yet received any reports on snowfall amounts in that
area.   The shortwave responsible for this activity will be kicking
east this morning, with any lingering shower activity wrapping up
shortly after sunrise across Mohave county.

Behind that wave, a weak ridge will build into the region, though it
will be a "dirty" ridge with periods of mid and high cloud cover
streaming through at times. In fact, widespread cirrus overcast is
likely to move in from the west late this afternoon and evening.
Temperatures today will be ~10 degrees below normal behind the
departing cold front, and will warm a few degrees Monday but remain
cooler than normal.

.LONG TERM...Tuesday through Sunday.

Continued active weather pattern is expected through much of the
upcoming week. A weak, low amplitude ridge will remain across the
region through Tuesday before an AR with tropical Pacific origins
teams up with another Pacific NW trough to bring ample moisture and
precip chances across the region mid to late week.

Despite ridging Tuesday, mid and upper level moisture will begin to
seep into the region creating partly cloudy to mostly cloudy skies
and increased chances for precip mainly for western Inyo and San
Bernardino counties. Based on the latest models, best chance of more
widespread precip should occur between Wednesday afternoon and
Thursday morning. Medium range models have started to agree on the
timing and dynamics of this storm, though confidence remains low to
moderate as model trends have weakened similar storms over time.
That being said, with more consistency amongst the latest models,
decided to increase POPs a bit with mostly widespread chances of
rain/snow showers. Because of the tropical natural of the moisture
source, snow levels will increase to 8500`-9000` by Wednesday
morning, limiting snow accumulations to the highest elevations
mostly above 8000-9000 ft.

Main impacts with this next system are precip accumulations and
winds. Storm total QPF over the course of 4 days has about 0.2-0.5"
across most deserts and valleys. Total snow amounts over the same
time period have 0.4" on the Spring Mountains and up to 20-50" on
the eastern Sierra crest. Gusty southerly winds begin to pick up
late Wednesday afternoon and early evening as an approaching trough
axis digs into northern California. Gusty winds stick around through
Thursday with more relaxed winds Friday as the system moves east and
weakens. Increased cloud cover will accompany the deep moisture
plume through Thursday before returning to partly cloud skies
Friday. Beyond Thursday, models diverge and confidence remains low
on the evolution of the approaching trough. Temperatures hover
around normal through much of the week.


.AVIATION...For McCarran...Breezy north or northwest winds are
expected through midday before weakening in the afternoon, likely
becoming light easterly and then variable by this evening.
Increasing high clouds above 20k likely late in the afternoon,
becoming BKN-OVC by sunset.  Widespread mid and high clouds will
linger overnight with light winds.

For the rest of southern Nevada, northwest Arizona and southeast
California...Light winds are expected today for KBIH and KDAG with
light northwest winds expected across TAF sites further east,
possibly gusting to 20 knots in the morning hours before weakening.
Otherwise, increasing high clouds are expected this afternoon,
becoming BKN-OVC above ~20k this evening and overnight, especially
north of a KDAG to KIGM line.


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



LONG TERM...Kryston

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