High Wind and Winter Weather in Nevada, March 6, 2021

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
443 PM PST Fri Mar 5 2021

.UPDATE...

A quick look at the latest guidance and we are going to go ahead
with an upgrade to wind advisory for the Tahoe Basin down through
Mono county for tonight into Saturday morning. The strongest winds
will be from South Lake Tahoe down through Lee Vining, mainly
around midnight to around 6AM Saturday morning. As precipitation
begins to spillover tonight, this will help to temper the winds.
Expect to see wind gusts in the valleys up to 55 mph with wind
prone areas, including canyons and exposed passes over US395 in
Mono County with gusts of 60-80 mph at times during the wee
morning hours on Saturday.

The other variable that needs to be discussed is the elevated
fire danger tonight as the winds increase. The lower valleys along
the US-395 corridor, mainly around Bridgeport, Walker, Coleville
could see elevated fire danger from the high winds and low
humidity tonight. We have had below average precip in the last
few weeks and we haven't even gotten into the "green-up" of
vegetation yet. Given these conditions our fire danger will likely
be elevated through the early morning hours before sunrise, but
the main limiting factor will be that the winds come through
overnight and not during the peak daytime heating and dryness.
-Hoon

&&

.PREVIOUS DISCUSSION... /Issued 258 PM PST Fri Mar 5 2021/

SYNOPSIS...

A fast-moving system will bring a modest Sierra snowfall along
with breezy to windy conditions tonight into Saturday. High winds
are possible for wind-prone areas along Highway 395 in Mono County.
A pattern change to more active weather is likely with cooler
temperatures, breezy winds, and periodic chances for rain and snow
for much of next week.

SHORT TERM...

A cold front stuck near the Oregon and northern California coast
will make a dash for northeast CA and western NV late tonight into
Saturday morning as it gets a push from a sharp upper low that will
move over northeast CA/northwest NV Saturday. Snowfall totals across
northeast CA above 5000-5500 feet and in the high Sierra north of
Ebbetts Pass still look to pick up a modest 2 to 6 inches. In the
Tahoe Basin and for foothills out into far western NV, the rapid
movement of the system is expected to keep snowfall totals light
at best. For the Tahoe Basin, between 0.5" and 2" is expected with
a 20% chance for 2-4". Out into the foothills (above ~5000 ft)
north and west of Reno, a dusting to 0.5" is possible with a 20%
chance for up to 1". Any snow should abruptly cut off before 10 AM
Saturday as the system high-tails it off into Idaho and northeast
Oregon.

Of larger concern than the modest Sierra snowfall is the strong
wind possibilities ahead of the front, especially from far southern
Douglas County south along Hwy 395 to around Lee Vining. The High
Wind Watch raised for Mono County for late tonight and Saturday
morning continues with another look for a possible upgrade
expected this evening. The potential for strong wind gusts over 50
mph remains enhanced for the South Lake area and for many spots
in the lee of the Sierra, especially for wind-prone spots along
Highway 395 in Mono County. The wind flow aloft is mostly south to
west which favors 395 north of Mammoth (NW flow aloft would favor
Mammoth southward) for the strongest wind potential.

Travelers along Highway 395 late tonight and Saturday morning
need to be prepared for sudden bursts of strong winds (60-80 mph
possible) at the mouths of canyons in Mono County. While not the
main focus, the southern and southwestern parts of Douglas County
could also see a few hours with strong wind gusts up to 60 mph as
a cold front approaches after midnight.

After the cold front moves through Saturday morning, winds will
switch to west to northwest with the threat for high winds falling
off quickly. However, it will still be breezy (gusts 20-35 mph)
with concern for boaters remaining through at least early afternoon.
Temperatures will fall closer to seasonal normals Saturday (highs
40s Sierra and 50s lower valleys). -Snyder

LONG TERM...Monday into mid-March...

Main Message: Expect a pattern change through mid-next week with
colder temperatures, breezy winds, and chances for precipitation.

The long term forecast continues to be a mixed bag of potential
outcomes at this time. Forecast confidence remains moderate to even
somewhat strong in regards to the overall synoptic pattern over much
of the West next week with the GEFS, EPS, and 3-7 Day WPC Clusters
all showing a deep, longwave trough.

Wind...Moderate Confidence: Not anticipating any significant wind
under this pattern as guidance shows much of the strong, upper-
level jet support positioned over southern California and
extending into the desert Southwest during this time. However,
according to the majority of ECMWF ensemble members sampled at
several locations throughout the forecast area, Monday afternoon
into the evening hours looks to be the strongest wind day of the
week as the trough with embedded cut-off low pressure system treks
along the California coast. This potential setup could result in
region-wide west- southwest gusts in the 20-45 mph range. Of course
higher gusts likely for the Sierra ridges.

Temperatures...Moderate to Strong Confidence: Below average high
and low temperatures are expected from Monday through Thursday of
next week across the region under the trough. Nothing crazy, but
it will most likely feel chilly, raw, and dreary out there with
the assistance of partly to mostly cloudy conditions and scattered
rain/snow showers. As of now, temperatures look to begin a
warming trend Friday as high pressure tries to build in from the
west. However, 25% of the Day 7 WPC Clusters do show the low
pressure system sticking around a bit longer which could delay
warming to the weekend.

Precipitation...Low Confidence: The trend has been on the
downward path and continues to be that way this afternoon. Given
the time of year, these early Spring, cut-off lows tend to be a
tricky thing to forecast when it comes to precipitation for the
Sierra and western Nevada. Following this trend using a blend of
the NBM, GFS, ECMWF, RFC, and WPC QPF guidance... total snow and
liquid forecast amounts have decreased accordingly from Monday
through Wednesday, but not by much compared to last night's
forecast. The bulk of the moisture should take place over the
Sierra with help from orographic lift leading to sufficient
forcing. A sharp cut- off in amounts is likely at this time for
much of western Nevada thanks to shadowing. A bit more confident
in this scenario panning out due to the parent southerly flow and
lack of forcing as the low progresses southward along the coast by
Wednesday. As it stands now, the NBM snowfall probabilities have
a 45% chance for greater than 4" of snow by Thursday for
communities around Lake Tahoe and a 35% chance for greater than 8"
for Donner Pass. As previously stated, most of the precipitation
and snowfall is likely to take place along the Sierra crest and
western slopes with a few inches to trace amounts for the western
Nevada foothills and into the valleys. Having said this, low
confidence exists in this forecast at this time due to the
potential pattern. We could end up with a wetter scenario with the
possibility for deformation bands to setup or we could see very
little moisture if the low decides to split with most of its
energy missing the region altogether and focused more towards the
south. As of now, we are gravitating more towards the drier
scenario, but with a grain of salt.

Conditions look to begin improving on Thursday with precipitation
chances diminishing as high pressure builds in from the west.
Tranquil conditions with warmer temperatures is possible for Friday.
A more stable pattern is probable for next weekend into mid-March,
but confidence in that is pretty much non-existent at this time
given multiple different outcomes according to the long range
ensemble data. -LaGuardia

AVIATION...

South to southwest breezes have picked up to between 20-30 kts for
much of northeast CA, far western NV, and for west-central NV
along and south of Hwy 50. Winds may ease back in the lower
elevations for a while this evening before increasing/peaking
late tonight into Saturday morning. Winds will bring turbulence
and periods of winds shear, possibly low-level within a few hours
around the frontal passage.

The cold front will bring a quick band of snow to the Sierra between
10z-14z Saturday with a few light showers into western Nevada. A
couple inches of accumulation on the runway are possible for KTRK/KTVL
with perhaps a dusting for KMMH. Spotty showers in western Nevada
are unlikely to yield accumulation on runways (just wet tarmac at
best). Anticipated widespread mountain obscuration late tonight into
Saturday morning with rapidly improving conditions before noon.
-Snyder/Dawn

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 7 PM PST Saturday for Pyramid Lake in
     NVZ004.

     Lake Wind Advisory until 10 PM PST this evening for Lake Tahoe
     in NVZ002.

     Wind Advisory from 10 PM this evening to 10 AM PST Saturday for
     Lake Tahoe in NVZ002.

CA...Wind Advisory from 10 PM this evening to 10 AM PST Saturday
     CAZ073.

     Lake Wind Advisory until 10 PM PST this evening for Lake Tahoe
     in CAZ072.

     Wind Advisory from 10 PM this evening to 10 AM PST Saturday for
     Lake Tahoe in CAZ072.

&&

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http://weather.gov/reno