Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 162156
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
156 PM PST Sat Dec 16 2017

.SYNOPSIS...
North to northeast winds will continue to be strong overnight on
Lake Tahoe and over the Sierra Crest. Elsewhere, the winds will
slowly diminish with cold temperatures continuing through the
remainder of the weekend. Slow warming is expected into Tuesday
with weak inversions. A fast moving, but potent system will bring
gusty winds and snow to the area Wednesday with very cold
temperatures behind it.

&&

.SHORT TERM...
Minor adjustments to the forecast with colder overnight lows under
clear skies tonight. Other changes were to the winds for Tuesday
night ahead of the next system. Tonight, the changes made earlier
this morning are on track as ridge gusts have already hit 100 mph
and Lake Tahoe has seen 30 mph sustained winds. Expect these winds
to continue through 06Z this evening before gradually backing off.
The Lake Wind Advisory extension issued earlier looks good.

Expect a cold night in areas that decouple tonight under clear
skies. Warming aloft begins tomorrow and continues into Monday
with inversions forming again. These do not look to be as strong
as last week. There will be more mid and high level cloud cover
beginning tomorrow night limiting the amount of radiational
cooling.

Expect a mild day Tuesday ahead of the next system with it rapidly
moving in Tuesday night. Winds will be the biggest issue Tuesday
night. While 700 mb winds do look to peak at near 60-70 kts, this
does not look like a widespread big wind event. With the rapid
movement of the system, large breaking mountain waves are
unlikely. That said, a brief period of high winds is possible
just ahead of the front when the best mixing occurs. Precip looks
to be post-frontal, similar to most inside sliders so snow levels
were lowered with the idea that most if not all precip will be
behind the cold front.

.LONG TERM...Wednesday onward...
An "inside slider" shortwave trough will push a strong cold front
through the area on Wednesday. Models have continued to be
remarkably consistent with this system (something that is not too
common with sliders) perhaps due to the sharp boundary of the cold
air mass and strength of the cold front. Overall, this system is
shaping up to be a very fast moving front with most precipitation
occurring as snowfall as snow levels sharply drop as the front
passes. As such, its character looks like a brief hour or two
burst of snowfall with the front.

Strong frontogenetical forcing coupled with good instability and
moisture will produce efficient microphysics for snow growth. Snow
amounts are still low end confidence but its looking like an inch or
two with front on Wednesday so far. The fast moving nature of this
system should reduce the chances heavy localized banded amounts
which can happen with fronts like this that stall. Overall, keep an
eye on the forecast on Wednesday if you have travel plans.

As this system departs, we will develop another period of gusty
northeast winds across the ridges through Thursday. These winds may
persist into next weekend as upper level ridge builds across the
west coast. The large scale pattern favors a blocking pattern that
will keep big Pacific storms away from our area with perhaps a
chance for another cold slider-like system for the end of the month.
Fuentes

&&


.AVIATION...
Gusty NE ridge winds to continue with gusts to 90 kts. Severe mtn
wave turbulence is likely near the Sierra Crest due to mountain
waves through 06Z this evening. Winds then begin to diminish with
peak gusts only to 30-40 kts by 18Z Sunday. Light winds then
overall into Tuesday before the next system arrives. This one
looks stronger than last night with gusty winds, mtn wave
turbulence, LLWS and a brief period of MVFR/IFR conditions in
SHSN.

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 10 AM PST Sunday for Lake Tahoe in
     NVZ002.

CA...Lake Wind Advisory until 10 AM PST Sunday for Lake Tahoe in
     CAZ072.

&&

$$

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



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