Winter Weather in Nevada, April 13 to 14, 2021

Area Forecast Discussion
National Weather Service Reno NV
329 AM PDT Tue Apr 13 2021

.SYNOPSIS...

A colder system will affect the region today through Wednesday.
Winds will increase today area-wide, strongest south of US-50 this
afternoon. There will be scattered rain, snow, and pellet showers
today through Wednesday along with low end chances for
thunderstorms. It will be much colder through Wednesday before
warmer and drier conditions return for the end of the week and
through the weekend.

&&

.DISCUSSION...

Winds will be on the increase today as a cold front ushers in a
cutoff low that drops directly over the region. Northerly wind
gusts of 25-35 mph will be the rule for areas north of
approximately US-50. Choppy conditions are expected on area lakes,
but the short duration of the stronger speeds will keep us from
issuing any Lake Wind Advisory products this morning. Areas south
of US-50 are expected to see stronger winds, per EPS meteograms
and NBM, as they will have longer to heat up, creating more of a
thermal gradient. Here, southwest gusts of 35-50 mph are possible,
strongest for Mono and southern Mineral Counties. This could
bring travel difficulties for high profile vehicles along US-395
and US-95, especially for wind prone locations near the mouths of
canyons. Winds will turn NW-N late this afternoon for these areas,
but will still remain breezy post-frontal. Areas of blowing dust
are possible in the west central Nevada Basin and Range as well as
increased fire danger. Please see the fire section below for
additional details.

Scattered rain and snow/snow pellet showers are on tap today through
Wednesday. Models continue to show better agreement on where the
higher potential liquid totals exist, helping to somewhat improve
forecaster confidence, despite cutoff lows being inherently
tricky in this area. Currently, portions of the Sierra and Sierra
Front are favored, mainly from Bridgeport to Portola, with
possibly over 0.25" of liquid (~30% chance for that amount at any
given point). Some portions of the Tahoe Basin have the potential
for qpf amounts over 0.75" based on the upper ends of the ensemble
range (75-90th percentile). These showers will be convectively
driven, so coverage will be hit or miss, possibly even over short
distances. Lighter showers with variable liquid amounts are
possible elsewhere across the region along with a 15-20% chance
for thunderstorms each afternoon mainly focused in the Sierra and
Sierra Front. If the current forecast holds true, higher elevation
Sierra passes such as Mt Rose Hwy, Sonora Pass, Ebbetts Pass,
Monitor Pass, and Tioga Pass could see several inches of snow.
Accumulations are likely to be short-lived during the daylight
hours given the time of year. For backcountry recreation -- there
is potential for snow totals in the high Sierra from Leavitt Peak
to the Sierra County Crest on the west side, and portions of the
Carson Range on the east side (7500'+), to reach 6-12 inches,
with a 1 in 5 chance of occurring.

The other big change will be much colder temperatures compared to
the recent warmth with highs struggling to get out of the 50s today
and Wednesday in even the warmest locations. The wind today will
make it feel that much colder. Lows will drop near or below
freezing, especially outside of urban centers, Wednesday and
Thursday mornings. Protect any sensitive early season vegetation.

This low will slowly exit eastward with a warming and drying trend
starting on Thursday. Temps will be back above normal by Friday,
reaching 10-15 degrees above normal by Sunday-Monday. We have
potential to make a run for the first 80 degree day of 2021 at KRNO
on Monday. NBM has a 35-40% chance of this occurring, which is also
close to the record of 82 degrees for April 19. No big wind events
on the horizon, with typical afternoon westerly breezes.

Going into the following week, a couple deterministic models are
hinting at another trough passage or even a possible closed low, but
there is little ensemble agreement for this and the 8-10 day WPC
cluster analysis is favoring ridging with continued dry conditions
at this time. -Dawn

&&

.AVIATION...

A cut off low drops directly over the region today into Wednesday.
This will bring gusty winds today along with the potential for
blowing dust in the Nevada Basin and Range. There will be a period
of wind shear along the cold frontal boundary this morning north of
US-50 and this afternoon south of there. North to northwest winds
will be enhanced for terminals north of US-50 (KSVE-KTRK-KRTS-KRNO-
KCXP-KLOL-NFL) with gusts 25-30 kts possible during this time. The
strongest gusts from the southwest are expected to take place for
areas south of US-50, including KMMH and KHTH, with gusts 30-45 kts
possible. Winds to shift to the west-northwest for these locations
by late Tuesday afternoon, becoming lighter, but still gusty.

Scattered rain and snow/snow pellet showers are on tap today through
Wednesday along with a 15% chance for thunderstorms each afternoon.
Currently, portions of the Sierra and Sierra Front are favored,
mainly from Bridgeport to Portola, with spotty coverage elsewhere
across the region. There may be periods of reduced CIGS/VIS with
the showers along with terrain obscuration. There could be a brief
period of snow accumulation for Sierra terminals (KTVL, KTRK,
KMMH), but any accumulation will be short-lived given the time of
the year and runway warmth. -Dawn

&&

.FIRE WEATHER...

No significant changes to the fire weather forecast overnight with
the incoming low pressure system forecast to create gusty winds
and low humidity combining to create a period of increased fire
weather danger in southern Mono County today. A Fire Weather Watch
is in place for zone 274 from 11 am through 8 pm today.

The primary area of concern for our CWA is the low elevations of
southern Mono County (Swall Meadows & Chalfant Valley in particular),
with Red Flag Warnings in effect through southern Nevada and
portions of southern CA, into AZ, and UT.

Winds and RH - Ahead of the front today winds will begin to pick
up out of the southwest by late morning (around 10 am), with
gusts up to 40-50 mph in southern Mono County through early
evening (around 10 pm). Humidities are expected to remain very
dry, with min RHs below 15% until the front, and moisture,
arrives in the late afternoon (around 4 pm).

Fuels - Very dry early season conditions exist in lower elevations
of southern Mono County where severe to extreme drought
conditions exist. In conversations with local fuels experts,
typical spring green up has barely begun, meaning these fuels
could be available to burn, especially in the lower elevations
without any snowpack. Multiple sites around the eastern Sierra and
western Nevada are at "peak fire season" values.

By late afternoon RH will start to climb with winds switching to
the northwest and cool conditions behind the front. Showers are
likely along and behind the front tonight into Wednesday morning.
Chances for wetting rains have increased to around 50% around the
Tahoe Basin and portions of western Nevada, but chances for
wetting rain remain below 10-20% in the low valleys of southern
Mono County where the highest fire weather concerns exist. -Zach

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...Fire Weather Watch from 11 AM PDT this morning through this
     evening below 8000 feet in CAZ274.

&&

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