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000 
FXUS65 KREV 161129
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
329 AM PST Sat Dec 16 2017

.SYNOPSIS...

Brisk start to the weekend with north winds and below average 
temperatures today. Breezy winds today will bring improved air 
quality to the valleys with strong east winds along the Sierra 
crest through tonight. Temperature inversions redevelop for the 
start of the week before another cold front arrives midweek.

&&

.SHORT TERM...

Fast moving cold front and associated band of light precipitation
is currently moving southeasterly through western Nevada. 
Precipitation amounts have been mostly as expected with reports 
mostly between 0.01-0.10". In all but the lowest valleys, 
precipitation fell as snow, but warmer ground temperatures at mid
elevations prevented snow from sticking to most surfaces. With 
temperatures hovering right around freezing it's possible some 
surfaces could re-freeze in some colder mountain valley locations.
Best advice is if the road/sidewalk looks wet, prepare for 
slippery conditions. 

At this time (3:30 AM) the band of precipitation has moved south 
of Interstate 80, stretching from Markleeville to Fallon. Along 
the eastern Sierra some upslope flow is projected to occur and 
could result in slightly higher precipitation and lingering 
showers into the morning hours in Alpine, northern Mono, and 
southern Lyon counties. 

Breezy northeast winds, increased moisture, and below average 
temperatures today will make the morning feel quite brisk. On a 
positive note, winds today should be sufficient to bring clean 
air back into the urban areas that have experienced a stretch of 
decreased air quality. Winds at upper elevations along the Sierra 
crest have already turned northeasterly and begun to strengthen, 
with sensors along the crest gusting up to 50 mph. Easterly winds
along the crest will strengthen today and last through tonight. 
Winds gusts of 75-100 mph are not out of the question along the
ridgetops as very strong temperature gradient sets up along the 
Sierra crest. A Lake Wind Advisory is in effect today for Lake
Tahoe with the highest wave heights expected along the southwest
shores. 

Generally light winds can be expected Sunday into Monday with
daytime temperatures quickly rebounding Sunday into Monday and 
overnight temperature inversions quickly redeveloping. -Zach 


.LONG TERM...Tuesday onward...

A weak ridge will begin to shift east on Tuesday ahead of the next 
trough due in Wednesday. Valley inversions will likely persist 
Tuesday as mid level flow will not increase substantially until 
after sundown Tuesday.

A strong cold front along with strong winds look to accompany a 
slider-style system through the northern Sierra and western Nevada 
on Wednesday. The cold airmass behind the front should lower snow 
levels to all valley floors by Wednesday afternoon with accumulating 
snowfall possible. Models show good agreement in pushing this system 
through the area, but as typical with slider systems, the 
uncertainty will be with timing and intensity. Nonetheless, this 
system has been showing good instability and frontal forcing along 
with more moisture when compared to this weekend's system so travel 
impacts could be a bit more widespread. Based on the persistent 
track of this low and its fast movement, snowfall amounts (while 
possibly impactful to travel) are expected to remain generally on 
the light side. Simulations range from only a dusting to a couple of 
inches. 

As this system departs, we will develop another period of gusty 
northeast winds across the ridges by 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 storms away from our area and a continuation of the dry 
conditions as we round out 2017. Hohmann

&&

.AVIATION...

Cold front and associated band of showers was tracking along the 
Interstate 80/Highway 50 corridors early this morning. Web cams 
showed some light accumulations around the Tahoe Basin, otherwise 
runways were wet at lower airport sites where temperatures remain 
too warm and some rain was still mixing in with the light snow. This 
band will continue to move quickly to the southeast with showers 
ending at KNFL by 14Z and lingering through mid morning along the
higher terrain of Mono,southern Lyon and western Mineral 
Counties. Biggest impact will be terrain obscurement and periods 
of MVFR in the eastern Sierra from KMEV-KMMH through 18Z. 
Otherwise, improving conditions are expected as drier air moves 
into the region this afternoon. Gusty northeast winds will develop
over the ridges today and continue into Sunday with gusts to 70 
kts. Hohmann 

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 10 AM this morning to 10 PM PST this 
     evening for Lake Tahoe in NVZ002.

CA...Lake Wind Advisory from 10 AM this morning to 10 PM PST this 
     evening for Lake Tahoe in CAZ072.

&&

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