Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 172217

Area Forecast Discussion
National Weather Service Reno NV
217 PM PST Tue Jan 17 2017


A more active storm pattern is expected to bring a series of
storms to the Sierra and western Nevada Wednesday through the
weekend. The first moderate storm Wednesday into Thursday will
bring snow and wind to the Sierra with wind shear impacts to
western Nevada. Another storm is expected by Thursday night with
the potential for a strong storm for the end of the weekend.



Main changes today were to bump up winds for Wednesday evening as
the 700 mb winds ramp up to 50+ knots. Also raised snow amounts
some right along the Sierra crest where the best forcing will
exist with the splitting storm moving in.

Stratus decks in western Nevada valleys have weakened and lifted
out of most western Nevada valleys, although high level clouds are
moving in and haze remains trapped under weak inversions. Haze
may persist through tomorrow especially in the metro areas where
particulates have built up.

The biggest forecast challenge today is how much the winds are
going to be able to mix down into western Nevada valleys Wednesday
night. Strong winds will surely impact the Sierra and very likely
mix down into the foothills of western Nevada. However there may
be enough of a stable inversion in some valleys that resist mixing
out and may only see occasional strong gusts.

Either way Sierra ridges could easily gust to 100+ mph with
substantial wind shear and turbulence in the lee of the
mountains. In Sierra valleys and western Nevada foothills winds
could gust 30-40 mph. Valleys below 5000 feet will be the biggest
question mark with some areas mixing out and becoming windy while
others may stay calm through much of the event and then suddenly
become gusty for a few hours late in the evening.

Precipitation-wise the storm is still forecast to split as it
comes onshore which will create a strong mountain shadow. The
Sierra crest could see around 1.5 inches of QPF with Reno only
receiving 0.15 inches or less. Snow levels are expected to drop
fairly rapidly in the Sierra with most precipitation falling as
snow. Right along the Sierra crest could see 8-16 inches of snow
with snow amounts rapidly dropping off to the east.

While this storm is much weaker then the storms earlier in the
month, snow and wind could still cause significant travel
challenges. With saturated soils and some trees still retaining
heavy snow, falling trees could continue to be a problem in the
Sierra. Thursday afternoon there will be a short break in
precipitation as the next system is pushed into the region along a
185 knot jet. -Zach

.LONG TERM...Friday Morning through Tuesday...

Model simulations still on track with two more storms following the
Wed-Thurs storm, although predictability through the end of the week
could be a tad tricky due to the splitty nature present in the
large scale pattern. The second storm is forecast to move into
the Sierra and western NV Fri-Sat with the third storm projected
for Sun- Mon. Confidence is high for the second storm, but medium
on snow potential and impacts. For the third storm on Sun-Mon,
confidence is medium in a storm, but low on impacts (which could
include snow, rain, and wind). Let`s take a look at what we`ve got
right now.

Storm #2 (Friday-Saturday)

Latest simulations are in good agreement with precipitation
beginning in NE CA and the Sierra early Friday morning. Forecast
model soundings indicate that the atmosphere will be unstable enough
to promote spillover into Western NV by late Friday morning. Snow
levels will be right around the valley floors, so precipitation may
initially be a wintry mix before turning to all snow midday. There
may be some initial wind gusts before the spillover occurs,
especially in wind prone locations, around 40 to 50 MPH.

Then we have a bit of a break from early Saturday through early
Sunday. The Sierra may see very little in the way of a break and
could experience continuous snow showers from Friday through the
weekend. During breaks in the precipitation the winds could become
stronger, especially in western Nevada with wind gusts around 35 to
45 MPH.

Storm #3 (Sunday-Monday)

IF this storm remains on track with latest simulations, it has the
potential to be a decent wind and snow producer. This is obviously
not a guarantee, as we have seen with previous systems 5-6 days out.
Here is what we are seeing now. This storm continues to look more
dynamic than the second storm. Heaviest precipitation still appears
to be in the early Sunday to Sunday afternoon time frame. The GFS
continues to kick the system out a bit quicker than the ECMWF, so we
will hedge towards a middle solution for continued precipitation
into early Monday. One feature I am noticing today, is that both the
ECMWF and the GFS develop a sharp band of precipitation late Sunday
into early Monday morning from northern NV dropping down through the
I80 corridor. It is too early to pinpoint the exact location of such
a band developing, but that would result in localized higher rain
and/or snow amounts. This winter storm appears to have it all, from
latest simulations, which would include a bit of strong winds and
also some rain/snow.

Bottom line: Keep an eye on the forecast through the week. Travel
impacts will range from driving issues in the Sierra (and
potentially down into Western Nevada) to aviation turbulence from
Wednesday through at least next weekend.

For those of you who grow weary of the active weather, it does look
like there may be a light at the end of the tunnel. By
Tuesday/Wednesday, model simulations are hinting at a potential
break in the active pattern as a ridge considers returning to the
West. -Edan


Some valley areas finally had a chance for some clearing skies this
afternoon and evening. Southerly flow should continue to increase
through tonight which should further assist with clearing out the
low level clouds. Winds aloft will also begin to increase overnight
resulting in the increased potential for low level wind shear and
turbulence for most terminals by early Wednesday morning.

Precipitation moves into the Sierra and northeast California early
Wednesday. Gusty surface winds are likely east of the Sierra by
Wednesday afternoon...but the precipitation will hold off there
until late Wednesday night. MVFR/IFR conditions are likely in the
Sierra and northeast California by 00z Thursday and MVFR conditions
are possible east of the Sierra by 09z Thursday. 20/Edan


.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory from 10 AM Wednesday to 4 AM PST
     Thursday NVZ005.

     Lake Wind Advisory from 10 AM to 4 PM PST Wednesday for Lake
     Tahoe in NVZ002.

     Winter Weather Advisory from 4 PM Wednesday to 4 AM PST Thursday

CA...Winter Weather Advisory from 10 AM Wednesday to 4 AM PST
     Thursday CAZ070-071.

     Winter Weather Advisory from 7 PM Wednesday to 7 AM PST Thursday
     above 6000 feet in CAZ073.

     Lake Wind Advisory from 10 AM to 4 PM PST Wednesday for Lake
     Tahoe in CAZ072.

     Winter Weather Advisory from 4 PM Wednesday to 4 AM PST Thursday



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