High Wind and Winter Weather in Nevada, December 16, 2016

Area Forecast Discussion
National Weather Service Las Vegas NV
315 AM PST Fri Dec 16 2016

.SYNOPSIS...A strong Pacific storm system will impact the area
through today with gusty winds and scattered showers. A sharp drop
in temperatures will follow on Saturday, bringing sub-freezing
temperatures across much of the Mojave Desert by the end of the
weekend.
&&

.SHORT TERM...Today through tonight.

Strong storm system moving onshore this morning will bring scattered
showers along with strong winds to portions of the area today. Most
of the precipitation is expected to fall during the morning hours
with showers becoming more isolated in the afternoon. Some of the
mountain locations have been seeing some decent rainfall totals
while valley locations have generally seen less than a tenth of an
inch. A few locations in the Spring Mountains have seen between an
inch and a half and two inches. Snow levels have been fairly high
with this system and even at 230 am the temperature in Lee Canyon at
an elevation of 8600 feet is 35 degrees. Colder air is really not
expected to work into the area before this evening so snow levels
will remain fairly high through the day, but showers will also be on
the decrease with most of the area dry before the colder air
arrives.

The main concern for today will be the winds. So far we saw some
fairly high gusts during the late afternoon and evening hours, but
winds have generally decreased a bit overnight. However, stronger
winds are expected to return this morning as drier and more
subsident air begins to work into the area. All the hires models are
showing a rapid increase after 8am PST and and lasting into this
evening. The current high wind warnings we have out for portions of
San Bernardino and Inyo Counties look good along with the Spring
Mountains in southern Nevada. The models have been fairly consistent
in bringing some rather strong downslope winds into the Las Vegas
Valley late this morning through the afternoon. Although we were
expected the strongest winds to occur over the western foothills it
now looks like the strong winds may make it as far east as the
central valley. Localized gusts to 60 mph will not be out of the
question for portions of the valley and have elected to issue a high
wind warning for the Las Vegas Valley from 4am until midnight with
the strongest winds occurring between 9am and 5pm. Do not think that
the entire valley will see warning criteria winds, but feel that a
large enough area will. Winds will start to diminish this evening as
a cold front moves through the area and turning the winds to the
northwest. Much colder air will work into the valley with
temperatures dropping significantly on Saturday.

.LONG TERM...Saturday through Tuesday.

By Tuesday morning, dry air will be pouring in behind the departing
storm, and precip chances will be gone. The main concerns then
become post frontal north winds and cold temperatures. Wind speeds
will be maximized down the Colorado River, where advisories will
almost certainly be needed for Sunday and Monday, and beyond that if
the ECMWF verifies. The coldest air of the season thus far will be
in place for most of the CWA Sunday and Monday mornings. KLAS will
likely drop below freezing for the first time since February 3, and
temperatures will fall well below freezing in the outlying areas.
MOS guidance and local tools point to Indian Springs, Pahrump, and
Kingman as having the greatest chance for impacts such as burst
pipes, so hoisted a Hard Freeze Watch for NV zone 17 and AZ zone 3
for Sunday and Monday mornings. Will keep an eye on trends to see
whether this may need to be expanded. Did not make any changes
beyond Tuesday due to ongoing weather plus the future wind and
freeze concerns.
&&

.AVIATION...For McCarran...Gusty southwest winds are expected to
last through much of the day with strongest winds likely between 15z-
00z this afternoon. Wind gusts may approach 50 kts at times,
especially over the western half of the valley. Rain chances will be
greatest this morning then decrease during the day. Cigs around 5-6k
feet will be possible this morning, but should increase to around
12k feet by late morning and then clearing out by this afternoon.
Strong turbulence is likely through much of the day.

For the rest of southern Nevada...northwest Arizona...and southeast
California...Scattered showers through the morning then becoming
more isolated in the afternoon. Cigs down to around 5k feet at times
this morning, but will improve to around 12k feet or better by the
afternoon. Strong gusty winds will also be a factor with areas
around Inyo, San Bernardino and portions of Clark Counties seeing
gusts approaching 50 kts. A cold front will move through the area
this evening with gusty northwest winds behind the front along with
much colder air. Turbulence/mountain obscurations likely.
&&

.SPOTTER INFORMATION STATEMENT...Spotter activation is not
anticipated. Spotters are encouraged to report any significant
weather according to standard operating procedures...especially with
the storm today.
&&

Short Term/Aviation...Gorelow
Long Term...Morgan

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