Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 012115
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
115 PM PST Thu Dec 1 2022

...WINTER WEATHER IMPACTS CONTINUE ACROSS THE REGION...

.SYNOPSIS...
The current winter storm will continue to bring major impacts to
the Sierra and portions of western Nevada through tonight. Cold
temperatures arrive Friday during a brief break in activity.
Another potent winter storm will bring additional heavy snow with
travel impacts to the Sierra as early as the overnight hours
Friday into early Saturday. Snowfall impacts will likely then
spread into western Nevada through the day on Saturday.

&&

.SHORT TERM...(Through Friday Night)
Our current winter storm is well underway across the Sierra and
western Nevada. As of this writing, precipitation is just now
beginning to spillover into the leeside of the mountain ranges. We
have already seen impressive snowfall rates in Lassen and portions
of Plumas through the morning hours. Expect rates to tick up into
the afternoon as a NCFR brings in rates that may exceed roadway
plowing capabilities at times (along with very low visibility) and
result in even messier conditions as we head into the evening
commute... The greatest chance for snowfall accumulation across
western NV valleys will also be during this time. Rates could also
be impressive for a brief period of time in the valleys as well;
supported by forecast soundings at RNO suggesting a well saturated
isothermal layer in the ideal snow growth region (-18C to -12C).
Heavier snow will abruptly end this evening from north to south
and hi-res guidance looks to push the main precipitation south of
Tahoe by sunset and Mono county by midnight. Nevertheless, a few
showers here and there will still be possible; to account for
these lingering showers and allow time for roadway conditions to
improve - a 4am Fri end time to the winter weather headlines still
seems reasonable.

As far as temperatures go for Friday? It`ll be really cold. ENS
meteograms still indicate that the skies will quickly clear late
overnight, along with winds becoming much lighter. Couple that
with a fresh coat of snow on the ground and we`ll have the recipe
for rapid cooling. The timing of clear skies, however, will
dictate "how much" cooling we`ll see. But, expect single digit to
sub-zero morning lows in Sierra valleys and solid teens elsewhere
in western NV (but isolated single digits can`t be ruled out under
ideal conditions for some western NV communities). Highs will be
chilly, with everywhere only topping out in the upper 30s or
colder.

Enjoy the very brief break in weather as our next system will
work its way into the Sierra and NE California early Saturday. Hi-
resolution models have started to pick up on this system, and
snowfall may arrive into Mono county as early as midnight tomorrow
(Friday night), spreading north during the overnight and early
morning hours. Winter Storm Watches have been hoisted for this 2nd
storm - details will be highlighted more in the long term
discussion below.
-Dustin

.LONG TERM...(Saturday onward)

Our next storm is still on track to be colder, slower, and wetter
than today`s storm. However, the timing of the system looks to be
slightly earlier than expected, with impacts to the Sierra
now arriving as early as Friday night.

A closed low developing off the coast of southern California will
provide a moisture tap for the initial surge of moisture on Friday
night. High-resolution models, including the HRRR and NAM, suggest
snow showers will intiate along the southern Sierra crest into Mono
county late Friday night. Showers will spread northward along the
Sierra through the morning, with impacts to the Tahoe Basin by late
morning. Snowfall intensity looks to remain relatively lower than
the first storm, and generally continuous through Monday morning.
However, higher snowfall rates are expected Saturday afternoon into
Sunday morning for the Sierra as the main upper-level closed low
system that has been tracking southward off the Pacific coast swings
into northern California. This system will provide additional lift
and moisture Saturday afternoon across the Sierra, consequently
leading to some periods of heavier snowfall and potentially allowing
snow showers to spill over into northeastern California and western
Nevada. The ECMWF Extreme Forecast Index notes a widespread area
of enhanced CAPE across the Sierra into western Nevada on Sunday,
suggesting showers may become convective, potentially even
producing thunder and lightning through the afternoon. The main
storm should taper off through Monday morning, though some
lingering showers may persist as the long wave trough hangs over
the western US through the first half of next week.

While the weekend storm will see relatively lower snowfall rates in
comparison to the first storm, it will hang around our region for a
longer period of time. Therefore, storm snow totals will likely be
similar or even higher than those observed from today`s storm.
Blended guidance suggests a nearly certain (97-99%) chance for at
least a foot of snow, a 80-90% chance for at least 2 feet, and a
30-50% chance for at least 3 feet along the Sierra crest. Chances
for snow across far Western Nevada has increased slightly to a
50-60% chance for at least an inch of snow and a 20-30% chance for
at least 2 inches.

South-southwest winds are expected to increase along the Sierra
on Saturday morning ahead of the main closed low system. Gusts as
high as 80+ mph are possible along the Sierra crest through Sunday
morning. Gusty winds will once again raise concerns for
backcountry recreation and aviation. Visit
sierraavalanchecenter.org for more information on avalanche danger
if you plan to head into the backcountry this weekend.
-Whitlam

&&

.AVIATION...
A winter storm will continue to bring heavy snow accumulations to
the Sierra with accumulations possible for lower elevations through
the evening as snow levels fall. There will be a brief break Friday
into Saturday AM, and then another potent winter storm will approach
the area with more snowfall for the Sierra and western NV.

* Winds have gradually lessened as snow pushes into the region this
  afternoon. The LLWS along with brisk northwest winds will persist
  a bit longer (06-09Z Friday) in the eastern Sierra of Mono County
  including KMMH.

* Snow is producing IFR/LIFR conditions for the Sierra terminals
  this afternoon. Heaviest snowfall rates with substantial runway
  accumulations look to be in the will continue through 0Z Friday
  for KTVL/KTRK and 22Z-06Z at KMMH as a heavier band of snowfall
  migrates southward; rates of 2" per hour will be common with a
  peak of 3-4" per hour possible along the front. For western NV
  terminals, a rain/snow mix will transition to all snow around 22z-
  0z with periods of MVFR/IFR conditions. Snow totals for western NV
  will be around 0.5-1" for lower valley airports, but there is a
  25% chance for 2" at RNO and 50% chance for 2" at MEV/CXP.

Edan

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 4 AM PST Friday NVZ005.

     Winter Storm Warning until 4 AM PST Friday NVZ002.

     Winter Storm Watch from late Friday night through late Sunday
     night NVZ002.

     Wind Advisory until 7 PM PST this evening NVZ001-004.

     Wind Advisory until 1 PM PST this afternoon NVZ003.

     Winter Weather Advisory until 4 AM PST Friday NVZ003.

CA...Winter Weather Advisory until 4 AM PST Friday CAZ070.

     Winter Storm Warning until 4 AM PST Friday CAZ071.

     Winter Storm Watch from late Friday night through late Sunday
     night CAZ071.

     Winter Storm Warning until 4 AM PST Friday CAZ072.

     Winter Storm Watch from late Friday night through late Sunday
     night CAZ072.

     Winter Storm Warning until 4 AM PST Friday CAZ073.

     Winter Storm Watch from Friday evening through late Sunday night
     CAZ073.

&&

$$


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