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Area forecast discussion 
National Weather Service Reno Nevada
221 am PST Friday Dec 19 2014

Synopsis...
chances for rain and snow will persist north of Highway 50 through
Saturday as couple of weak systems brush northeastern California and
western Nevada. High pressure will then build Sunday through the
first part of next week. A cooling trend and snow are possible for
Christmas evening.

&&

Short term...
minor adjustments made to the ongoing forecast this morning as a
weak system brushes across northeastern California and northern
Nevada.

A precipitation band ahead of the main cold front moved through
Lassen and Plumas counties early this morning bringing snow
showers to those areas. The web cam at Bogard rest area (around 5600
feet) showed snow accumulating quickly between midnight and 1am
under the precipitation band. Travelers should check Road
conditions before heading out this morning as roads may be slick or
snow covered. As the cold front approaches the region, snow
levels will remain near 6000-6500 feet around Interstate 80 and
4500-5000 feet near the Oregon border. Light snow amounts of up to
a couple inches are possible above 5500 feet through the morning
with higher amounts to 6 inches near the Sierra crest.

The system pushes through the region tonight with moist upslope flow
allowing residual showers to continue along the crest. The next
round of precipitation pushes into areas from the Tahoe basin
extending north into northern Lassen, Washoe, and Churchill counties
as a result of warm air advection. Again the best chances appear to
remain right along the Nevada/Oregon border with chances dropping
off significantly further south. Model soundings continue to show an
isothermal layer which may allow snow levels near the Oregon border
to remain near valley floors, but snow levels will be on the rise
late Saturday into Sunday as the warm front pushes through.

After this system passes through Saturday night, the ridge amplifies
off the West Coast bringing a warming and drying trend. Skies will
remain fairly cloudy under the dirty ridge pattern, especially north
of Interstate 80, which will help to moderate temperatures
overnight. Otherwise ridging through the weekend may allow surface
inversions to develop which will result in faster warming for ridge
top temperatures than the valleys. Weishahn

Long term...Monday through Christmas...

High pressure over the west will give way around middle week as low
pressure moves into the West Coast. Models solutions showed a
moderate amount of agreement so forecast confidence is medium in a
system moving into the region on Christmas evening. Models continue to
show a front reaching northern California and northwest Nevada on
Wednesday. The front should increase gusts to near 45 miles per hour in the
lower elevations, which will help clear out any haze/pollutants in
the valleys and may warm highs into the 50s to near 60.
Precipitation may start to move into areas north of Interstate 80 by
late Wednesday afternoon, then across the Reno-Tahoe area during
Christmas evening. Those traveling Christmas evening and Christmas morning
should keep an eye on the forecast for potential impacts due to
snow over the Sierra passes and on the Nevada Valley floors. After
the system passes, a cold north surface flow could keep afternoon
highs on Christmas day in the 20s and 30s. Brong

&&

Aviation...

Cold front moving through the area is producing snow and IFR
conditions in the northern Sierra with scattered showers and MVFR
conditions east of the Sierra. The front is forecast to weaken as it
moves south this morning, though there is enough moisture and
instability to produce snow around the Tahoe basin with isolated to
scattered showers across western Nevada. There could be an inch or
two of accumulation on tarmacs/runways at ktrk and ktvl today. The
front will also kick up gusts to near 30kts this morning along and
south of ktrk-krno-klol.

A few light showers should break into the vicinity of krno and kcxp
by 17z, but temperatures may warm enough to get the snow level off
the Nevada Valley floors. Brong

&&



Rev watches/warnings/advisories...
Nevada...none.
California...none.
&&

$$

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