Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 161017
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
217 AM PST Tue Jan 16 2018

.SYNOPSIS...A weak disturbance will brush the southern Sierra and
central Nevada today, though precipitation look low for today.
Ridging builds back in for midweek before a more active weather
pattern sets up for the end of the week. A cold Pacific system
moving onto the West Coast will likely bringing winds and a chance
of precipitation the the Southwest United States by Friday.
&&

.SHORT TERM...Today through Thursday Night.

A weak shortwave is still expected to move through the area today.
Current mesoanalysis shows unimpressive radar returns thus far with
this feature as it moves ashore north-central California. Most of
the stronger radar signatures and precipitation reports at the
surface have been orographically driven thus far. As this piece of
energy moves eastward through the day, it will need to fight with an
impressive western ridge and is expected to split as it gets
absorbed into the mean anticyclonic flow. Given the current
observations to the west and the strength of the ridge over the
area, backed off precipitation chances for the Sierra and Central
Nevada areas this afternoon. This matched up well with model trends,
especially on the high res models. Wouldnt be surprised if this
shortwave did nothing but washout and bring a bunch of clouds to the
area today and no precipitation fell at all.

If precipitation were to develop and reach the surface, northern
Lincoln County looks to be the most likely location for
precipitation. Areas north of Caliente and Hiko may see some light
showers, with light snow possible above 8000ft but no accumulation
is expected.

The shortwave will exit the area tonight and another ridge will
build in behind it for Thursday. Expect quiet weather with mostly
sunny skies on Thursday as temperatures remain above normal.

The next system swings onshore the West Coast later on Thursday and
moves east towards the area Thursday night. Models continue to trend
slower this the eastward push of precipitation overnight as a cold
upper level Pacific trough moves into California. Adjusted precip
chances slightly to reflect this slower trend. Think the bulk of the
precipitation wont arrive until Friday. Winds overnight Thursday
will increase though, and higher elevations should start seeing
some stronger gusts through the night.
&&

.LONG TERM...Friday through Monday.

Still on track for a significant change in the weather as a storm
system impacts the region over the weekend, with the possibility
of a second, weaker storm affecting the southern Great Basin
Monday. For the first storm, the GFS is still swinging the system
through more quickly than the ECMWF, although the difference
between the two operational runs is quite a bit less than it was a
couple of days ago. Precip chances will be underway in the Sierra
by Friday morning, then spread south and east, possibly making it
as far south as I-40 Friday night and Saturday morning. Precip
chances will end from west to east on Saturday as the trough axis
moves by and ushers in much cooler air. The cold air will pour in
at nearly the same time as the rain chances end, with a few
snowflakes possibly mixing in as the rain ends even as low as
3500-4000 feet. The cold air will also knock high temperatures
down about 5-10 degrees from Friday to Saturday over much of the
Mojave Desert, with the cold air staying in place at least through
Sunday. A couple of days ago, it looked like warm air advection
ahead of the next system approaching the West Coast would start a
warming trend in our area on Monday, but that warming trend looks
much more muted today. Any precip chances for Monday will likely
be confined to the Sierra and the higher terrain of the southern
Great Basin.
&&

.AVIATION...For McCarran...Other than broken cigs above 20fkt, no
impactful weather is expected across the airspace through Wednesday.
Winds will generally be light through the period with typical
diurnal trends.

For the rest of southern Nevada, northwest Arizona and southeast
California...A weak disturbance will brush the southern Sierra and
central Nevada this afternoon with cloud bases near 12 Kft MSL and
some light precipitation near mountain tops. The rest of the region
will continue to see dry weather with light winds under periods of
clouds above 20 Kft. Localized daytime gusts around 20kts knots will
persist near Laughlin-Bullhead City.
&&

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

$$

SHORT TERM/AVIATION...Wolf
LONG TERM....Morgan

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