Area Forecast Discussion
Issued by NWS Reno, NV

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452
FXUS65 KREV 201147
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
347 AM PST Mon Nov 20 2017

.SYNOPSIS...

A warm and weak system will bring light rain and very high elevation
snow to portions of northeast California and northern Nevada into
tonight before drier weather returns through at least Wednesday
night. A low chance for light rain and very high elevation snow
returns late in the week. Mild temperatures are expected Tuesday
through the rest of the week.

&&

.SHORT TERM...

Increasing winds aloft with an incoming disturbance nearing the
Pacific Northwest coast have induced better mixing for much of
northeast CA and extreme western NV overnight, with winds out in
the Basin and Range expected to pick up a bit by this afternoon.
This will allow for better mixing for the lower valleys and should
help to mediate air quality concerns.

Weak warm air advection precipitation will accompany the
aforementioned disturbance into tonight, with light rain possible
for the northern Sierra, northeast California, and Nevada generally
north of a Pyramid Lake to Lovelock line. Dry air ahead of the
incoming light precipitation over northeast CA is allowing snow
levels to be somewhere between 6,500 and 7,500 feet east of the
crest; however, snow levels should rise to around 9,000 to 10,000
feet east of the crest today with the warm air advection so impacts
from the light precipitation will be minimal.

The ridge strengthens over the West Tuesday, which will deflect
most of the moisture and the storm track into the Pacific Northwest.
Temperatures will warm up through mid-week into the upper 50s to
upper 60s for valleys. Some guidance is hinting at lower valley
temperatures into the lower 70s, but our thinking is that inversions
will set up again by midweek as winds aloft decrease and clearer
skies allow for colder overnight lows. This will make it difficult
to fully mix and reach those temperatures. -Snyder/Edan

.LONG TERM...Thanksgiving into early next week...
The overall trend will be for cooling and a possibly more active
pattern. However, there is considerable disagreement between the
short waves in the GFS/EC and their ensembles. Overall, trended pops
a little higher as we head into early next week, but didn`t go that
high due to the timing uncertainty.

Thanksgiving Day the models are in good agreement with a weakening
wave passing by to the north into Oregon. Winds aloft increase a
little, but the biggest impact will be the increase in cloud cover
and chance of showers near the Oregon Border. The changes here
were to increase the cloud cover and also decrease temperatures a
bit. The cloud cover will have a pretty big impact on the diurnal
range if it is cloudy and Thanksgiving could be quite a bit cooler
than Wednesday in the valleys if this were to occur.

Friday may be the driest day between short waves before the next set
of waves arrive for the weekend into early next week. This is where
there is quite a divergence in timing between the models. The GFS
has a weakening system Saturday, dry Sunday with a stronger, colder
system Monday. The EC has the two waves closer together with moisture
for the weekend, but drier Monday. It is also warmer overall, but
not as warm as the current system. Until things become clearer, just
went with a chance for NE California and a slight chance elsewhere.
Winds may also be strong at times, but with the disparity went with
locally breezy conditions and gusty winds over the ridges for now.


&&

.AVIATION...
Areas of MVFR CIGS in NE CA today through about 03Z as a warm front
moves through with -RA. VFR conditions expected elsewhere. Winds will
be locally gusty through 00Z today as ridge winds gust to 60 kts.
Mtn wave turbulence will be widespread, but we are not expecting any
LLWS. Later tonight VFR conditions are expected and will likely
last into at least Wednesday. Locally gusty winds will occur in
the mountains with some mtn wave turbulence, but it likely won`t
be as strong as today.

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

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



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