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Area forecast discussion 
National Weather Service Las Vegas Nevada
826 PM PDT Tuesday Oct 25 2016

Synopsis...patchy fog could develop once again tonight otherwise
pleasant conditions are expected through Thursday. The next storm
system will impact the area Thursday night and Friday with yet
another system potentially impacting the southern Sierra Nevada
and central Nevada Sunday.

Update...much quieter this evening than 24 hours ago. Only change
was to reduce cloud cover overnight in accordance with satellite

Previous discussion...
304 PM PDT Tuesday Oct 25 2016

Short term...through Thursday.

Took all morning for low clouds and fog to dissipate leaving just
some shallow cumulus over the higher terrain this afternoon. Time
heights and relative humidity progs show a marginal amount of low level moisture in
place for patchy fog development late tonight/Wednesday morning.
Should not be as widespread as this morning, if any develops it
would favor parts of Lincoln, Clark and Mohave counties where the
greatest amounts of rain fell.

Ridge will amplify over the intermountain west Wednesday ahead of
splitting trough over the eastern Pacific. A southern stream wave
will be approaching the central California coast late Thursday
afternoon. Models still showing a tropical connection developing
between this trough and Hurricane Seymour with tropical moisture
being pulled up the California coast ahead of the trough. Some light
rain showers look to develop along the southern Sierra crest late
Thursday afternoon with the main precipitation shield coming
Thursday night. South to southeast winds will develop over parts of
Inyo, Esmeralda and Nye counties Wednesday afternoon then expand to
encompass more of the region Thursday.

Long term...Thursday night through Tuesday.

12z models are in slightly better agreement with timing and
placement of the upper low that is expected to impact the area
Thursday night through Friday. Models show the upper low to be just
of the central California coast Thursday afternoon with
precipitation spreading into the Sierra by Thursday evening. As the
low continues to progress east, precipitation will continue to push
east with most areas seeing at least a chance of rain by Friday
morning. The higher chances will remain over Inyo, Nye, Esmeralda,
and Lincoln counties where pops continue to get raised. It looks
like the best window for San Bernardino, Clark, and Mohave counties
will be between midnight and 9am Friday as a band of precipitation
looks to spread east overnight. Highest rainfall amounts will remain
to the north where totals could range between half an inch to an
inch with possibly over an inch of rain for the Sierra. Snow levels
look to remain around 10k feet so the highest peaks will see some
fairly significant snow. Areas to the south could see between a
tenth and a quarter of an inch of rain. One thing to watch for is
the potential for Seymour moisture to become entrained in the flow.
The GFS does show some higher precipitable water values working into region Thursday
night and early Friday. If enough moisture does arrive then qpf
amounts will likely be increased.

The models indicate that the system will exit to the east fairly
quickly with most of the precipitation out of the area by Friday
afternoon as a southwest flow develops ahead of another trough that
is expected to push into the West Coast Sunday. The models indicate
that the low over the weekend will be further north leaving most of
our forecast area dry on Saturday. The models are now indicating
that the upper low will continue to track a little further north
with very little moisture reaching the southern Sierra Sunday. Due
to the west flow, most of the moisture should get rain shadowed
leaving very little precipitation for our area. Left in some slight
chance pops on Sunday, but overall it looks like everything will
remain north.

Temperatures will remain a few degrees above normal Friday and
Saturday, but cool to below normal readings by Sunday through

Aviation...for McCarran...with a fair amount of low level
moisture left around the region can not rule out patchy fog develop
early Wednesday morning. Based on forecast soundings for the center
of the valley do not expect McCarran to be impacted so will not
include mention in forecast but could see some low clouds around the
edge of the valley. Otherwise, high clouds will start increasing
Wednesday afternoon. Winds should be under 8 kts and favor typical
diurnal directions.

For the rest of southern Nevada...northwest Arizona...and southeast
California...may see some patchy fog development in some of the
valleys of Lincoln, Clark and Mohave counties early Wednesday
morning. Otherwise looking at increasing high clouds Wednesday
afternoon. Winds should be under 8 kts and favor typical diurnal
direction, exception will be kbih where southeast wind gusts up to
20 kts.

Spotter information statement...spotters are encouraged to report
any areas of fog, including visibility estimates late tonight or
Wednesday morning. Otherwise quiet conditions are expected through


short term/aviation...Pierce
long term.............Gorelow

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