Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 050957

Area Forecast Discussion
National Weather Service Reno NV
157 AM PST Tue Dec 5 2017


Strong and gusty east winds will continue through this morning
across Sierra ridges with rough conditions expected on Lake Tahoe.
High pressure strengthens over the region this week bringing
inversions, cold nights, light winds, and reduced air quality for



Gusty east winds peaked overnight with Sierra ridge wind gusts
generally in the 60-80 mph range. Although Alpine Meadows Summit at
8643 feet did have a peak wind gust of 114 mph last night! Mono
county ridge wind gusts should begin to increase through the early
morning as the upper level jet sags south. Although ridge winds and
the temperature gradient will be weakening early this morning, Lake
Tahoe waters will remain choppy and rough, especially for areas from
Glenbrook to Homewood. The Lake Wind Advisory is in effect through
mid morning today.

High pressure amplifies across California and Nevada which will
introduce us to an extended period of dry conditions and light
winds. Increasing temperatures aloft will strengthen valley inversions
which will result in light winds, poor mixing, and degradation to
air quality for awhile. Weak winds and inversion base heights around
6,000-7,000 feet will result in trapped pollutants for the valley
areas with hazy conditions expected through the week.

An extremely dry air mass along with the strong valley inversions
will allow cold temperatures to materialize through the week. Many
locations will drop into the teens and lower 20s with the coldest
valleys into the single digits or below zero. Ensure vulnerable
communities as well as pets and livestock have shelter from the
cold. -Edan


The ridge remains in place, likely through the second or third week
of December based on longer range guidance. This means that the
forecast remains dry with light winds and inversions in place. The
stagnant conditions under the inversion will keep haze in place with
possible air quality concerns.

The one possible glimmer of hope for changing conditions mid-month
is a weakness under the ridge around southern California and
troughing around 140W. With the ridge as amplified as it is, this
could lead to an undercutting situation, especially given how strong
the jet is across the Pacific. On the downside, the deep trough over
the east may just reinforce the current longwave pattern. -Dawn



Easterly winds across ridgelines and western Sierra slopes will
continue through early morning. Sustained northeast to east winds of
45-55 kts with gusts of 60-75 kts across Sierra ridges will cause
turbulence and mountain wave activity along and downwind of the
Sierra through 18z, with lesser impacts thereafter as winds
decrease. For valley locations, peak winds are likely to be 5-10

The winds are likely to mitigate widespread fog development,
however patchy fog is possible through the Martis Valley, including
KTRK, the next several nights/early mornings.

As a ridge of high pressure strengthens across the west this week,
inversions will lead to hazy conditions and possible reductions in
slantwise visibility. -Dawn


.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 10 AM PST this morning NVZ002.

CA...Lake Wind Advisory until 10 AM PST this morning CAZ072.



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