High Wind in California, December 20, 2017

Area Forecast Discussion
National Weather Service Las Vegas NV
318 AM PST Wed Dec 20 2017

.SYNOPSIS...Big changes in store over the next couple of days as a
cold front sweeps through the region. Strong winds, much cooler
temperatures, and a chance of rain and snow showers will be in store
later today through Thursday. Cooler and dry conditions will then
persist into the holiday weekend.
&&

.SHORT TERM...through Friday night.

Satellite showing area of high clouds which enhanced over parts of
Inyo County and south central Nevada last evening starting to break
apart as it moves east. Elsewhere, lower clouds are banked up
against the western Sierra slopes while cooling cloud tops
associated with the cold front is just entering far northwest
Nevada.

Overall, forecast was changed little through Friday night. Surface
observations showing strong southwest winds as far south as the
Mammoth Airport this morning. Those stronger winds will sag south
and encompass the eastern Sierra Slopes of Inyo County through
midday. Hi-Res models showing little support for downslope winds
making it all the way into the Owens Valley this morning but its
something that will be monitored.

Elsewhere, gusty prefrontal west-southwest winds develop midday
across northern San Bernardino County, southeast Nevada and
northwest Arizona. Nearly at the same time postfrontal northerly
winds will develop in Esmeralda County and spread south into Inyo and
central Nye Counties during the afternoon. Eventually those stronger
postfrontal northerly winds will reach our southern zones early this
evening. Those northerly winds may slacken off a bit tonight but
will increase once again Thursday morning before beginning to weaken
late Thursday afternoon. Gusts up to 50 mph possible in some valley
locations while gusts approaching 60 mph possible in the higher
terrain.

Mix of rain/snow showers along the cold front will turn to all snow
behind the cold front as colder air sweeps in. Lincoln County still
looking like the area to see greatest accumulation of several inches
tonight. Some light flurries continue into Thursday near the Utah
border with both Lincoln and Mohave Counties. Elsewhere, it will be
dry but blustery with gusty north winds and colder temperatures.

Any lingering north winds will be concentrated into the lower
Colorado River Valley Friday while temperatures remain several
degrees below normal. Some of the coldest morning lows we have
experienced are possible Friday and Saturday mornings. Some Freeze
products may be necessary.

.LONG TERM...Saturday through Tuesday.

A return to mild and dry weather is in store for the long term as
high pressure rebuilds along the West Coast.  This will keep the any
Pacific storm systems blocked from approaching the region and
delivering any potential precipitation, and will also promote
gradually warming temperatures for the beginning of next week.  MOS
guidance suggests temperatures returning into the 60/70s across most
of the Mojave Desert as early as Sunday but tempered the warming
trend slightly given the likelihood of valley inversions this time
of the year. Nonetheless, above normal temperatures and continued
dry weather is expected.
&&

.Fire Weather...Due to the very dry Fall, fuels for this time of
year are quite dry. Given the strength of the winds, very dry air,
and fuel susceptibility, a Red Flag Warning is in effect for the
eastern slopes of the southern Sierra and Owens Valley of Inyo
County. A Red Flag warning is also in effect for the Spring
Mountains and Sheep Range along with the lower elevations of the
Colorado River Valley through Thursday afternoon.
&&

.AVIATION...For McCarran...Ahead of a cold front expect
strong, gusty southwest winds with speeds between 20-30 kts. Most
gusts will likely be up to 45 kts but its possible that winds could
briefly gust to 50 kts between 00z and 03z. Between 02z-04z, winds
will shift to the northwest and remain gusty as the cold front
passes through. Anticipate moderate turbulence downwind of the
mountains. Periods of high clouds will lead to SCT skies from this
evening through Wednesday afternoon. CIGs may drop to 7-9 kft this
evening with the cold frontal passage.

For the rest of southern Nevada, northwest Arizona and southeast
California...A low pressure system will lead to a strong, gusty
south-southwest winds ahead of quick moving cold front. Anticipate
southwest wind speeds between 20-30 kts and gusts between 35-50 kts.
Expect an abrupt shift to the northwest as the front passes, with
similar speeds to the earlier southwest winds. Anticipate moderate
turbulence downwind of area mountains. High clouds will lead to SCT
skies. Along the cold front CIGs lowering 5-7 kft associated with
rain showers quickly changing over to snow showers. Mtns obscured
especially in Lincoln County where snow showers will be most
widespread.
&&

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

Short Term/Aviation/Fire Weather...Pierce
Long Term...Outler

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