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FXUS65 KREV 222250
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
250 PM PST Wed Nov 22 2017

.SYNOPSIS...

Very mild conditions will prevail through Saturday with a few record
highs threatened. Most areas will remain dry although very light
rain is possible Thursday in northeast California and far northwest
Nevada. Saturday is expected to be very windy ahead of a strong
cold front which will bring snow to the Sierra and northeast
California Sunday and Sunday night. It will be much colder early
next week.


&&

.SHORT TERM...

Strong high pressure is currently over the region with warming
aloft and strong valley inversions. The strong inversions today
have kept the valley temperatures a bit cooler than we saw
yesterday, so it looks like we will probably not be breaking any
record temperatures at the Reno airport. SOme areas that are just
above the inversions today have hit some very warm temperatures
in the 70s. These strong inversions and residual moisture from
last weeks rains have causes form very atypical widespread fog
around Lake Tahoe today. The fog that normally burns off by mid
morning has stuck around all day and will likely fill in even more
tonight after sunset.

For Thanksgiving a system moving through the Pacific Northwest
will help to flatten out the ridge over northern CA/NV, along with
bringing some increased winds for the ridges and some very light
rainfall to the northern Sierra. Not expecting much in the way of
rainfall amounts, generally less than 0.10" and snow levels should
remain very high above 10000 feet. The record high on Thursday
for the Reno Airport is another soft record at 69 degrees. If we
mix due to the increased winds we could get close to that record
for Thursday. High pressure builds back into the region on Friday
as the next Pacific storm moves closer to the West Coast, making
for another mild and pleasant day across the region.

As we go into Saturday, the low pressure system will be starting
to push onshore, with 700mb winds increasing to nearly 70kts by
late Saturday afternoon. These strong pre-frontal winds will be
enhanced by the very tight temperature and pressure gradients as
the front moves towards the area. Latest model trends have been
colder behind the front, thus also stronger with the gradients and
winds in the Sierra and along the Sierra Front. Model sounds also
look favorable for downslope winds with inversions near the
Sierra ridgetops. Wind gusts of up to 60 mph are possible in the
valleys with ridge winds over 100 mph. A High Wind Watch has been
issued for the Sierra and Sierra Front zones Saturday afternoon
through Sunday as this strong front moves towards the area. Some
initial precipitation will begin to move into the northern Sierra
after midnight Saturday night and into early Sunday morning, which
will help to dampen the winds for those areas, although the winds
along the Highway 395 corridor will continue overnight and into
Sunday. Hoon

.LONG TERM...Sunday through Tuesday...

The forecast is on track for very strong winds Sunday, increasing
rain/snow Sunday afternoon, and a strong cold front arriving Sunday
night. Delays and chain controls are likely in the Sierra from
Sunday afternoon through Monday morning. Holiday travelers with
routes over the mountains should keep an eye on the forecast and
conditions, and have alternate travel plans.

Strong gusty winds will continue Sunday into Sunday night, with
damaging winds possible along the Sierra Front. Expect Sierra
ridge gusts over 100 mph at times from the southwest. Valley gusts
along the Sierra front range are likely to be 50-60 mph, but
stronger gusts over 65 mph are possible along the 395 corridor.

Expect precipitation to begin mainly as rain Sunday for most areas
below 8,500 feet. The precipitation begins mainly north of I-80 then
slowly spreads south and east into Sunday afternoon, mainly in the
mountains. Western Nevada remains mostly dry through this time
except for the Tahoe Basin and north of Gerlach. The snow level
forecast (medium confidence) call for snow levels to fall 1000-1500
feet Sunday, affecting the passes sometime Sunday afternoon.

Sunday night the strong cold front will move through with snow
levels falling to valley floors near and north of Highway 50.
Several inches of snow are likely for the passes, possibly even down
to Lake Level in the Tahoe Basin and to 5000 feet in Lassen County.
Mono County is likely to see some snow down to 7000 feet.

For Monday, the GEFS mean indicates the trough axis could still be
west of the Sierra. This suggests some potential that snow could
impact Monday morning commutes across western NV (30% chance).
Otherwise, temperatures will be much colder behind the front, near
average or slightly below average. Of course, it will feel quite
cold due to the brisk WNW winds and compared to the recent warm
weather.

Ridging rebuilds Tuesday-Wednesday with lighter winds and warming
temperatures for the mountains. Valleys will remain cold beneath a
moderate inversion as the likely clear skies result in good
radiational cooling. JCM

&&

.AVIATION...

IFR FZFG is possible again for tonight around the Tahoe Basin and
Sierra Valley. VFR conditions are expected for other areas. Ridge
winds will be increasing tonight and into Thursday-Friday with
ridge gusts around 50kts creating some potential for mountain wave
turbulence.

A potent Pacific storm will move into the region Saturday into
Sunday with strong winds for 36+ hours. Ridge winds of 50+ kts,
strong mountain waves with turbulence and LLWS are likely Saturday
and Sunday. Rain and snow will move in with the greatest impacts
Sunday and Sunday night with IFR conditions likely in the Sierra
and brief periods of MVFR CIGS in Western NV overnight Sunday
night. Hoon

&&

.REV Watches/Warnings/Advisories...
NV...High Wind Watch from Saturday morning through Sunday afternoon
NVZ003-005.

High Wind Watch from Saturday morning through Saturday evening
NVZ002.

CA...High Wind Watch from Saturday morning through Sunday afternoon
CAZ070-071-073.

High Wind Watch from Saturday morning through Saturday evening
CAZ072.

&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno
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