Winter Storm Watch 2, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
322 AM PDT Wed Mar 11 2020

.SYNOPSIS...

A trough of low pressure will bring some light rain and higher
elevation snow showers well south of Highway 50 today. Temperatures
will remain above average through Friday. A strong storm arrives
this weekend with strong winds followed by heavy mountain snow,
possible accumulating lower valley snow, and much colder temperatures.
Cold temperatures and snow showers linger into next week.

&&

.SHORT TERM...

The axis of a trough of low pressure off the southern California coast
extends northeast into the eastern Sierra and portions of western
Nevada this morning. Light rain and higher elevation snow has developed
along the axis across southern Mono County with precipitation totals
between 0.02" and 0.16" so far this morning per HADS and RAWS sites.
Snow levels are running near 7000 feet with temperatures along Highway
395 south of Mono Lake in the lower 30s and light snow reported at
the Mammoth airport. With precipitation rates light and temperatures
in the 30s, roads have managed to remain just wet as seen in CALTRANS
cams in Mono County. With all this in mind, it would appear impacts
from light snow are minimal this morning and no chain requirements
are in place as of this writing.

Some of the latest high-res models continue to indicate some rain and
higher elevation snow showers popping up under the trough axis across
Mono County, and perhaps western Mineral County and near the crest
in Alpine County, this afternoon. This is unlikely to cause much
of a travel issue as snow levels rise and roads heat up. Elsewhere
today, expect sunny to partly cloudy skies with highs 5 degrees or
so above average (mid 50s to mid 60s for valleys).

Thursday afternoon looks to be breezy across the region with northeast
winds gusting up to 25 mph for valleys and slopes as a surface high
builds in from the north. Winds decrease Thursday night and switch
around to the southwest before ramping up by Friday evening into early
Saturday ahead of this weekend's significant winter storm.

Thursday and Friday will most likely continue to be relatively warm
for this time of year with temperatures above normal. This will change
drastically as colder air impacts the Sierra and western Nevada this
weekend. Read the long term section for the "business end" of the
forecast. -Snyder

.LONG TERM...Saturday through next week...

High confidence this morning in a potent winter storm to affect the
Sierra and western Nevada beginning Saturday and possibly lasting
into Monday. Changes were to continue to increase the precip chances
from Saturday night through Sunday night as well as increase the QPF.

Ensembles are in very good agreement now with the low remaining
offshore through Monday morning. With the low just offshore, it is a
heavy snow pattern for the Sierra and potentially for western Nevada.
While it is still 3-4 days away, some rough details can be determined
for the Saturday through Sunday night time period...

WINDS: Still looks quite windy Saturday with gusts of 100+ mph
possible over the Sierra ridges and gusts of 45-60 mph in the lee
side valleys. This will create strong crosswinds, particularly on
north-south running highways. Some dust is likely to kick up off
the sinks of western Nevada as well.

SIERRA SNOW: Will begin sometime Saturday afternoon and continue
through Sunday evening. The heaviest snow looks to be around the
Tahoe Basin as the front stalls there for a period of time, but this
can change. Rough snowfall amounts could exceed 2 feet along the
Sierra Crest with around a foot possible in the Tahoe Basin. Several
inches are possible for the 395 corridor in Lassen and Mono Counties.

WESTERN NEVADA RAIN/SNOW: This is a bit tricker as it depends on timing
of the heaviest snowfall. It may briefly start as rain but otherwise
it is likely to become all snow Saturday night. Timing is everything
here as snowfall during the day will really limit accumulations.
However, if it's overnight snowfall accumulation could be significant,
particularly for the 395 corridor from Minden to Doyle, including Reno.
As of right now, models are showing the heaviest precip timing from
03-18Z Sunday which would almost be ideal for snowfall on the valley
floors. Still, only put this as about a 30% chance for all the snow
to occur during this time. The range of valley floor accumulation
is quite large...from nothing to over 6". The chances of no valley
accumulation is still about 40-50%.

For Monday into Tuesday, there could be another burst of heavy snow
Monday (many EC ensembles) or more just snow showers. The upper low
will linger into Tuesday with more snow showers and light mountain
accumulations possible. It will remain cold with highs 10-15 degrees
below average. Overnight lows will also be chilly with single digits
possible in the Sierra valleys under clear skies assuming fresh snow.

For the latter half of next week, it is looking drier with temperatures
returning close to average for mid-March. There could be another
system dropping out of the north late next week, but it looks much
weaker with a better potential for an overland trajectory. That is,
it looks like any precip that could fall would be very light. X

&&

.AVIATION...

VFR conditions north of KBAN to KHTH this morning and only scattered
mid cloud cover. South of there, areas of MVFR CIGS/CIGS in -SHSN
through 18Z. Then we expect VFR conditions for all areas although mtn
tops near KMMH could be obscured at times. Any showers that do develop
over the Sierra this afternoon look to remain west of the crest. Then
VFR conditions Thursday and Friday with increasing winds late Friday.

A potent Sierra storm for the weekend with strong winds, mtn wave
turbulence, and LLWS Friday night into Saturday. This will be followed
by snow Saturday afternoon into Sunday evening. Sierra terminals will
see IFR conditions at times with several inches of snow possible for
the terminals. Western Nevada terminals will be IFR/MVFR at times
with lighter runway accumulations possible Sunday morning if the
heaviest snowfall falls during that time. X

&&

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

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