Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 132145

Area Forecast Discussion
National Weather Service Reno NV
145 PM PST Wed Dec 13 2017


High pressure will bring dry conditions along with valley inversions,
cold nights, and light winds through Friday, with reduced air quality
in urban valleys. Pollutants should decrease with improved air
quality by Friday night and Saturday as a weak system brings an
increase in winds. Inversions are likely to strengthen again
early next week as high pressure rebuilds overhead.


.SHORT TERM...through Saturday...

Introduced a low chance for showers for northeast California and
western Nevada Friday night and Saturday morning and lowered highs
Saturday 5-10 degrees, otherwise little change to the previous

High pressure remains in charge well into Friday, which should
keep conditions stagnant with seasonable afternoon temperatures
through Thursday and cold nights/mornings for valleys through
Friday morning. Temperatures Friday afternoon are currently
projected to creep up 3-6 degrees (over Thursday) in northeast CA
and out into portions of western NV as a weak trough of low
pressure approaches northern CA. While inversions are unlikely to
erode completely, some simulations predict that they will rise
some with warmer temperatures. This could allow pollutants/haze to
disperse somewhat in far western NV by late Friday afternoon. Farther
out in the Basin on Friday, inversions look to change little.

Friday night and Saturday morning, a few simulations are digging a
stronger and more consolidated trough back to near the Sierra
crest with light precipitation, while others keep the trough
disjointed and weaker with no light precipitation. Either solution
is certainly possible so the confidence for light, mainly snow
showers remains very low. In the strongest case, snowfall amounts
would be very light (less than 1/2") for Saturday morning. Still,
the trough should bring a shot of colder north flow for Saturday,
with the increased flow likely to scour out most of the valley
pollutants. -Snyder

.LONG TERM...The End of 2017.

2017 appears likely to end in the opposite fashion it began. No
big storms on the horizon with ensemble solutions showing a ridge
near the west coast. Now this doesn`t mean it will stay completely
dry, but the placement of the ridge favors a continuation of the
valley inversions with potential for cold systems to drop out of
Alaska and/or western Canada with relatively low moisture

Once the system for Friday Night and Saturday morning passes,
valley inversions will redevelop for Sunday and strengthen Monday
and Tuesday with noticeable haze redeveloping around the
population centers. Models bring another cold/dry system through
the Pacific Northwest and Great Basin late next week, but may only
be a brief break from the inversions. Brong



Mainly VFR with light winds (less than 8-10 kts) for valleys
through at least Friday morning. However, easterly winds will
increase late tonight and Thursday morning over the Sierra crest
as high pressure strengthens in the Great Basin. Gusts 30-45 kts
are likely to bring light to moderate turbulence over and west of
the Sierra crest into early Thursday afternoon.

With valley inversions remaining strong through Friday, slantwise
visibility will remain degraded during the daylight hours for
lower valleys, especially in the Reno/Sparks, Carson City, and
Minden areas. Increased northerly winds Friday night and Saturday
should clear much of the haze out, at least for a day or two.


.REV Watches/Warnings/Advisories...


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