Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 060932

Area Forecast Discussion
National Weather Service Reno NV
132 AM PST Wed Dec 6 2017


A prolonged period of high pressure is expected over northeast
California and western Nevada for the next week and beyond. This
will bring valley inversions, cold nights, light winds, and reduced
air quality for valleys.



High pressure will dominate the weather pattern resulting in dry
conditions, light winds, and valley inversions this week. Weak winds
and inversion base heights around 6,500 feet will result in trapped
pollutants for the valley areas with hazy conditions expected
through the week. Upper level winds will increase a bit as a weak
shortwave brushes by later this afternoon and into Thursday. Went
ahead and increased ridge winds for that time frame. Main impact
will be enhanced east winds for the ridges, but we could also see
choppy conditions at Lake Tahoe if some of these stronger winds
mix down to the lake surface.

Cold valley temperatures will occur each morning due to the presence
of inversions and a dry air mass. Many valleys will run 5-10 degrees
below season averages with lows expected to drop into the teens and
lower 20s with the coldest valleys into the single digits or below
zero. Temperatures aloft will warm through the week with high
temperatures becoming fairly uniform with elevation. Overall,
looking for temperatures to increase to the mid and upper 40s for
western Nevada valleys and the Sierra into the weekend. Fuentes/Edan

.LONG TERM...Saturday onward...

The ridge stays firmly 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. Temperatures will gradually warm
through the period with seasonably mild days and cool nights.

What did look to be a glimmer of hope for changing conditions mid-
month, does not look as favorable in recent forecast simulations.
Previous model runs showed a strong zonal jet across the Pacific,
which could have lead to an undercutting of the ridge, whereas
recent runs are significantly more amplified. This is likely to only
reinforce the current longwave pattern, especially given the deep
trough downstream over the eastern CONUS. -Dawn



An extended period of high pressure will produce light surface winds
and valley inversions this week. Inversions will lead to hazy
conditions and possible reductions in slantwise visibility.

A period of light to moderate turbulence is possible across the
northern Sierra this afternoon into Thursday morning as sustained
east winds reach 30 kts with gusts to 50 kts. Fuentes/Dawn


.REV Watches/Warnings/Advisories...


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