Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 160210

Area Forecast Discussion
National Weather Service Reno NV
710 PM PDT Sun Oct 15 2017


A few minor changes were made to some low temperatures tonight...
but not enough to change most of the zone forecasts. High clouds
are thinning a bit over the area and this...combined with
decreasing winds...should allow valley temperatures to fall rather
quickly through the late evening hours. Some of the colder
valleys may have temperatures closer to this morning`s lows while
the mid slopes and ridges could be near or warmer than this
morning. Otherwise...the forecast appears on track with a slow
warming trend early in the week then our first storm system of the
fall at the end of the week.


.PREVIOUS DISCUSSION... /Issued 207 PM PDT Sun Oct 15 2017/


A warming trend will start Monday as high pressure strengthens
over the Sierra and western Nevada. Valley inversions will remain
across the region through at least Monday with potential for
better mixing by Tuesday. Winds will become gusty ahead of an
incoming storm Thursday and Thursday night. Cooler conditions
with valley rain and mountain snow are on tap for the end of the
work week.


Inversion conditions were clearly present early this morning with
mountain top temperatures in the low 40s and many lower elevation
valleys in the teens and 20s. This means that mixing will be poor
today, with a gradual improvement the next several days. A very dry
air mass is in place aloft leading to poor humidity recoveries on
ridges and upper slopes the next few nights.

Monday, ridging becomes the dominant feature with warming
temperatures and clear skies. The warm and dry conditions will
continue into Wednesday, though the strength of the ridge weakens
due to an approaching trough.

Areas of smoke and haze are possible the week ahead from ongoing
wildfires in California, however impacts are unlikely to be anything
like what we experienced on Friday. The extent of the smoke/haze
will be largely determined by fire activity and the generally weak
transport winds. -Dawn


Top 3 things to know:

1. Winds increase and become gusty on Thursday/Thurs night

2. Increasing precipitation chances Thursday into Friday

3. Mountain passes could see snow Friday, especially above 8000 feet

The main focus for the long term continues to be a weak atmospheric
river (AR) tap interacting with a trough moving into the west coast
the end of the week. Winds will be increasing ahead of this feature,
with the strongest winds likely to be on Thursday, potentially
continuing into Thursday night. The upper and lower level winds are
somewhat disjointed, so while windy, we do not anticipate a high
wind event. The other forecast feature pointing toward weaker winds
is the fact the strongest winds aloft are now coming in Thursday
night and this also corresponds with increasing moisture. Peak gusts
look to be around 35-45 mph in most valley locations and about
double that for mountain tops.

The most likely period for the heaviest precipitation looks to be
Thursday night into Friday. Due to plenty of warm air ahead of the
system, snow levels will start high, likely around 8500-10000 feet.
They will drop off to 5500-6500 feet closer to the Oregon border and
6500-7500 feet south of Highway 50, on Friday behind a cold front.
As far as snow impacts to roadways, it will be a race between
exiting precipitation and approaching colder air. Snow is definitely
possible on mountain passes, but snow totals will largely be
determined by how quickly the cold air makes it into the region. At
this point, assume that passes above 8000 feet will see
accumulation, with the greatest uncertainty between 6500-8000 feet.

Please make note, this is a weak AR merging with an area of low
pressure and will not be like some of the extreme events we dealt
with last fall and winter. The details of the storm will be ironed
out in the upcoming days, so at this point, just be prepared for
windier and wetter conditions the end of the week.

Beyond this storm, the main storm track remains north of the region
with warming temperatures and predominately dry conditions expected
next weekend. Longer range models are hinting at this drier pattern
possibly continuing toward the end of October. -Dawn


Generally light winds and VFR conditions through Wednesday. The
one exception is the possibility of decreased slantwise visibility
from smoke in the central Sierra around KTVL/KTRK as smoke from
the Table Fire drifts in. A moderately strong storm is expected
Thursday/Thursday night with periods of gusty winds, rain, and
high elevation snow. Main impacts are expected to be from strong
ridgetop winds and periods of MVFR conditions for Sierra
terminals. -Zach


.REV Watches/Warnings/Advisories...


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