Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 200254

Area Forecast Discussion
National Weather Service Reno NV
754 PM PDT Sun Mar 19 2017


The only issue with the evening forecast is the presence of
relatively thick mid and high clouds along with a few light rain
showers...mainly over northeast California. The presence of these
clouds is likely to keep temperatures from falling as fast as
forecast through the evening and overnight hours. We have raised
overnight lows a few degrees to account for this. The latest short
range models are not enthusiastic with pcpn chances overnight. But
continued moist southwest flow will be over the region. Forcing
does not look impressive so we will lower pops a bit from roughly
I-80 south...but keep slight chance to low end chance pops over
northeast California and far northwest Nevada.

On a side note...Walker River Irrigation District has increased
releases from Bridgeport Reservoir on the East Walker and is
allowing more water to flow past Topaz Lake on the West Walker.
These higher flows will likely result in some minor low land
flooding along the East Walker River and below Yerington on the
Walker River in the days to come. Check our Flood Advisory for
updates to expected flooding.


.PREVIOUS DISCUSSION... /Issued 251 PM PDT Sun Mar 19 2017/


Mostly cloudy today with increasing winds on Monday. Valley rain
and mountain snow are expected Tuesday into Wednesday with gusty
winds continuing and periods of travel disruptions. Another,
stronger storm is likely for early next weekend with active
weather looking possible through the end of the month.


A weak frontal boundary shifting through northern CA/NV this
afternoon and evening is bringing spotty light showers to areas
north of approximately I-80 as evidenced on radar. Winds this
afternoon are breezy, with gusts of 15 to 30 mph, but will weaken
overnight. Winds will increase for Monday through Wednesday,
as a stronger system moves into the region.

Drier air will work into the west on Monday ahead of the system
slated to move into the west late Monday into Tuesday. This will
limit precipitation totals as the first wave of the storm reaches
the region Monday night, but the stronger secondary wave follows
right behind overnight into Tuesday. This will bring deeper
moisture into the area and also push a cold front through,
dropping snow levels in addition to bringing gusty winds. Overall
snow levels look to start in the 7000-8000 foot range Monday night
into Tuesday morning (lowest closer to the Oregon border),
falling to around 6500-7000 feet Tuesday night, then as low as
5500 feet by Wednesday.

The timing for snow levels falling has trended slower as some
warmer air is advected into the region ahead of the cold front.
This may mean that snow levels won`t fall to most Sierra pass
levels until midday Tuesday. Due to the slower timing on the snow
levels, and the bulk of the precipitation falling during the day
Tuesday when the sun angle is fairly high, impacts on roadways may
be lessened. Think along the lines of slushy or short lived snow
accumulation on passes, especially below 7500-8000 feet. The one
caveat with this is the fact that storms may become convective,
which could briefly lower snow levels by 1000 feet or more in a
heavier shower. This could lead to short periods of rapid snow
accumulation on roadways, but should quickly melt during the
daytime period. The upper level low moves over CA/NV on
Wednesday, with convective showers likely to develop. A mix of
rain, snow, and pellet showers are likely with periods of travel
disruptions, especially in the Sierra.

Liquid totals in the Sierra are expected to be in the 1-2"
range, with western Nevada seeing totals around 0.10-0.3". The big
question will be snow amounts in the 6500-7500 foot range on
Tuesday due to the uncertainty on how quickly snow levels may
fall. It could be anywhere from an inch or two of slushy
accumulation upwards of 6-8" depending on location and if
convective showers form. For areas above this, 8-18" is possible
from late Monday night through Tuesday.

Increasing mid level instability will produce a slight chance for
thunderstorms Tuesday and Wednesday afternoons. Am not expecting
storms to be widespread, but it would be impossible to pinpoint
locations at this point, so have kept broad brushed slight chances
in the forecast. -Dawn

LONG TERM...Wednesday through Sunday...

A shortwave ridge builds in on Thursday which will give the region a
short break in the precipitation before the next storm pushes into
the Sierra and western Nevada. The storm for Friday-Saturday
continues to look consolidated and less "splitty" in nature with
recent model simulations. The upper level jet has trended further
north, which will keep snow levels higher for a bit longer than
previous forecasts.

Winds will begin to pick up along the ridges late Thursday night
into early Friday morning ahead of the storm for the weekend with
typical winter storm wind gusts in the 80-100 mph range. Stronger
surface winds for the valley floors likely won`t materialize until
Friday afternoon but wind gusts around 40 mph will be possible for
the valleys. Snow levels appear to hover around 6500 to 7000 feet
initially before they drop with the cold frontal passage early
Saturday. The storm still appears to have a decent subtropical
moisture tap with it as well, so we could be looking at a quick hit
of rain and snow late Friday-Saturday morning. Areas that are
flooded or susceptible to flooding should be paying close attention
to the forecast this week. Keep flood mitigation measures in place
or close by. The storm does move through rather quickly so by
Saturday afternoon/evening there will only be some residual

Other than some light convective showers near the Oregon border,
Sunday will be more clear than previous forecasts for now. This
shortwave ridging on Sunday is short-lived as another storm appears
to be dropping out of the Gulf of Alaska potentially Monday
afternoon. -Edan


Southwest winds will remain breezy through this evening with gusts
to 25 knots possible. Ridge wind gusts will remain higher with
gusts to 50 knots possible through much of the week. There is
still a chance for some light showers north of Susanville and
Gerlach around 22z, but only isolated MVFR conditions. Winds will
begin to drop off after 06z for most terminals, but ridge winds
will stay up with mountain wave turbulence continuing to be a
possibility and impact.

A more significant system will impact the Sierra and western Nevada
Monday night into Wednesday. Ridgetop and surface winds will
increase Monday evening before precipitation begins to move into the
Sierra late Monday night and early Tuesday morning. Periods of
mountain snow and valley rain from late Monday into Wednesday are
expected along with MVFR and local IFR conditions likely.


No flooding is expected on mainstem rivers from the
Tuesday/Wednesday storm, however rivers will be running high. The
basins of greatest concern are the Susan and Middle Fork of the
Feather, which are at a lower elevation overall. This could push
the Susan River near Susanville and the Middle Fork of the
Feather River near Portola into monitor stage. If snow levels take
longer to fall than currently anticipated, further rises are
possible. The other mainstem river to be concerned about is the
East and West Walker Rivers, downstream along the mainstem of the
Walker River due to planned releases out of Topaz Lake and
Bridgeport reservoir beginning this evening. This could bring
minor flood impacts beginning Monday into Tuesday, lasting until
releases end. Please see the Flood Advisory for additional

Small creeks and streams are likely to see increases with this
storm in addition to Swan, Silver, White, and Washoe Lakes. While
this is not a major storm in terms of precipitation totals, runoff
will be very efficient given the antecedent wet conditions this
winter along with recent snowmelt. If you have flood mitigation
measures in place, it is recommended to keep this in place through
the spring. -Dawn


.REV Watches/Warnings/Advisories...


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