Area Forecast Discussion
Issued by NWS Reno, NV

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740
FXUS65 KREV 201451 CCA
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
359 AM PDT Mon Mar 20 2017

.SYNOPSIS...

Clouds and winds will increase this afternoon ahead of a spring
disturbance expected for Tuesday. 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.

&&

.SHORT TERM...

Sunny skies are expected early today as drier air works into the
region ahead of the incoming storm. High and mid-level clouds
should begin to develop this afternoon as low pressure off the
coast begins to push moisture into the region. Winds will pick up
today with gusts up to 25 to 35 mph this afternoon and gusts
along the ridges up to 80 mph.

Recent model runs have trended towards a splitting storm on
Tuesday with the main low pressure moving north towards the
Pacific Northwest coast. This continues the trend of higher snow
levels as the initial cold front is stretched north and slower to
move into the Sierra. This has also lowered total QPF for the
storm closer to 1-1.5 inches along the crest.

The main brunt of moisture is still expected during the morning
and early afternoon on Tuesday. Snow levels during that time are
expected to be in the 7000-8000 foot range dropping to around
5500-6000 feet by Tuesday night. Sierra passes could see some
slushy accumulation during the day if heavier precipitation drags
snow levels low enough, however, with warm road surfaces wouldn`t
expect much accumulation during the day. The bigger impacts to
travel could be Tuesday night (when snow levels begin to drop) or
Wednesday late morning (when convective showers could accumulate
snow on roadways).

With higher snow levels and bit lower QPF snow accumulations would
be a bit lower than previously forecast. Snow amounts below 7500
still remain the biggest question depending on how fast snow
levels fall. With rain potentially not turning to snow until later
on Thursday, leaning towards lighter accumulations of 2-4" range.
Above 7500-8000` accumulations could range from 8-16". Around the
Lake Tahoe Basin an inch or two could accumulate Tuesday night if
there is enough moisture left when snow levels finally make it
below 6000`. Recent models have split more of the precipitation
towards Mono County where less QPF was forecast earlier. Overall
confidence in snow amount is moderate at best with the storm
starting develop more of a spit and snow levels falling slower.

So, the biggest travel impacts could be Tuesday night or
Wednesday morning when colder temperature and convective showers
develop that could quickly produce light snow pellet showers that
stick to roadways. Monday night into Tuesday moderate rain
showers and possible periodic slushy accumulations could cause
some travel issues over the higher passes.

Winds could be gusty on Tuesday between periods of light
spillover. Forecasts have been pretty back and forth on spillover
timing which effects the potential for gustier winds. Current
thinking is that winds will get gusty (30-40 mph) ahead of the
spillover and then gust later in the afternoon as spillover
dissipates. The best period for showers in far western Nevada
looks to be in the morning and early afternoon on Tuesday when
instability and moisture advection are the highest. Could see
around 0.1-0.2 inches of precipitation during that time period.

Both Tuesday and Wednesday isolated thunderstorms will be
possible as mid-level instability increases under the cold pool.
Not expecting a widespread thunderstorms, but these convective
showers could cause isolated areas of accumulating snow pellets
down to around 5000 feet on Wednesday. -Zach

.LONG TERM...Thursday into next week...

Only a few adjustments made to the forecast in the long term.
Thursday looks like the break in any showers this week, although
there could be a stray shower or two in the Sierra and near the
Oregon Border. Otherwise, light winds and seasonable temperatures
are expected.

The next storm is set to arrive Friday into Friday night. The timing
continues to be slightly faster. In addition, the latest runs are
backing off on the intensity of the storm a bit. The latest model
suite also shows more of a propensity for the splits than previous
runs. Given the time of year, I am going to lean more on the idea of
a splitting system. In addition, the storm for early this week is
going to split more than models showed last week.

That said, the timing of the split will have a large impact on the
amount of precip. Splitting at the right time where the front pivots
on top of us would result in a wetter solution, whereas other
solutions would be drier. At this time, the going forecast
represents a good middle ground so we can trend one way or the other
depending on what is needed. The main change to this system was to
increase the snow levels at the start to the 7-8000 foot range and
to reduce winds a bit. Snow levels will drop with the front down to
near 5000 feet.

Saturday will see convective snow showers behind the surface front
as the cold pool aloft moves overhead. The next system is now faster
in the latest model runs and may move in by Sunday afternoon.
However, it will be moving in from the Gulf of Alaska and won`t have
as much moisture to work with. In addition, it will be colder with
snow levels likely to start out near or below 6000 feet. The active
pattern does look to continue into next week. However, the systems
look to be dropping more from the Gulf of Alaska so they will have
less moisture and be cooler. Wallmann

&&

.AVIATION...

Gusty winds are expected today from the S-SW with peak gusts again
near 25 kts, but otherwise VFR conditions expected with CIGS above
5000 feet. Winds increase on the ridges tonight ahead of the next
storm with local MVFR CIGS in -RA after 09z Tuesday in the Sierra.
More widespread MVFR CIGS in Sierra after 12Z with areas of the same
restrictions in Western NV from 15-00Z on Tuesday. An isolated
thunderstorm is possible during the afternoon hours as well. Winds
in the valleys could gust to 35 kts and there will be mtn wave
turbulence, but LLWS will be localized.

The showers will diminish Tuesday night, but increase again by
Wednesday morning with lower snow levels. Isolated -TSRASN are more
likely on Wednesday with quick, brief accumulation on runways in the
Sierra. Wallmann



&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno



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