Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 131138
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
338 AM PST Mon Nov 13 2017

.SYNOPSIS...

Gusty winds will impact most of the region today and tonight.
Rain and high elevation snow will be possible for northeast
California and the northern Sierra this afternoon and evening with
hazardous travel conditions over the Sierra Passes. An active
pattern remains through this week and into early next week with
wetter and windier systems possible.

&&

.SHORT TERM...

First system of the week will impact the region today and tonight,
though latest simulations are weaker on the winds and precipitation
totals. Biggest impact appears to be the winds along US-395 with
peak gusts 45-60 mph in wind prone locations from Lassen County
through western Nevada. Gusts should be limited to 35-45 mph
elsewhere, including US-395 through Mono County. Moisture depth is
lacking with this system, which means not much precipitation will
make it across the Sierra. Precipitation amounts up to 0.75 inch
is possible along the Sierra Crest mostly limited to western
Lassen county and southward along the Sierra Crest to about
Ebbetts/Sonora Pass. If everything works out, we`re looking at
around 6 inches of snow along the Sierra Crest above 7000 feet.
Travelers should expect wet and/or snow covered roads over the
Sierra passes for the commute hours this evening and early Tuesday
morning.

Wednesday and Thursday: A stronger and wetter low pressure system
will impact the Sierra and portions of western Nevada. Periods of
heavy rainfall and high elevation snowfall in the Sierra is looking
increasingly likely. Western Nevada will see impacts more from
strong gusty winds and will remain shadowed from heavier rainfall
until the arrival of a strong cold front Thursday morning.

Although models are showing broad agreement with this storm,
there still are some sticking points with timing and duration of
the heaviest precipitation. This has implications on expected
rainfall amounts and snowfall totals due to slower snow level
timing.

* SNOW LEVELS: Latest model guidance does agree on pushing the
  bulk of the subtropical moisture through ahead of the cold
  front. As such, snow levels in the Tahoe Basin could see snow
  levels remain in the 7,500-8,000` during the bulk of the
  precipitation through Wednesday evening. Current timing has the
  cold front dropping snow levels to pass level early Thursday
  morning where a change over to snowfall will occur but will also
  see precipitation intensity diminish. Mono County snow levels
  look to be in the 8,500` vicinity through the heaviest
  precipitation Wednesday night into Thursday morning.

 Timing is only at a moderate confidence level at this time so
 the bottom line is to keep updated on the forecast and if you
 have plans to travel over the main Sierra passes (80 and 50), it
 would be wise to go by early afternoon Wednesday to avoid VERY
 LONG DELAYS which could last until the snow winds down later on
 Thursday. In Mono County, only the highest passes (Tioga) should
 be affected until later on Thursday as colder air moves in.

* PRECIPITATION/SNOWFALL: Did increase expected precipitation
  amounts mainly through the Sierra in Alpine and Mono counties.
  However, also raised snow levels so snow totals increased mainly
  for areas above 8,000`. Overall 1 to 2 feet still looks solid
  above 8,000 feet, but areas between 6500-7500 feet in the Tahoe
  area are lower confidence and are trending towards more rainfall
  than snowfall with about 2-4" of accumulation possible after the
  cold front moves through Thursday.

* WIND DETAILS: Strong winds will also accompany this storm with
  the main window for gusty winds looking to occur Wednesday
  afternoon into Thursday morning. Winds across the Sierra will be
  strong and gusts over 100 mph are expected. Widespread gusts
  through Sierra valleys and western Nevada valleys will see gusts
  in the 40-50 mph range, but latest model guidance does show some
  potential for stronger gusts in the 50 to 60 mph range.
  Nonetheless, gusts this high will create travel impacts for high
  profile vehicles, dangerous boating conditions, and aviation
  impacts from low-level wind shear and turbulence. It would be a
  good idea to secure or store any loose outdoor items at this
  time. Fuentes

.LONG TERM...Friday through early next week...

Latest model simulations are favoring the Pacific Northwest and
coastal range with the upcoming series of storms moving into the
west coast as mean ridge develops over the southwest and Rockies.
The ECMWF has showed this positive height anomaly for several days
now while the GFS has been trending in that direction. Still, there
is some uncertainty with strength of incoming waves and being on the
northwest periphery of ridge, the southern extension of frontal
systems and accompanying moisture could reach as far south as the
northern Sierra. We will maintain some general low chance pops
mainly Sun-Mon while keeping temperatures above seasonal norms.
Hohmann

&&

.AVIATION...

Increasing winds aloft will result in periods of light to moderate
turbulence today with some LLWS possible prior to surface winds
shifting to the southwest and increasing this afternoon and evening.
Surface wind gusts this afternoon/evening will reach 25-30 kt at
most terminals with stronger gusts across northeast CA and
northwest NV.

The onset of precip will be a little slower...but should spread into
northeast California today and the Tahoe Basin by this evening.
Given high snow levels there should be little in the way of snow at
the KTRK and KTVL until early Tuesday morning. Accumulations are
unlikely although CIGS may lower to MVFR at times with terrain
obscurement during periods of steadier precipitation. VFR conditions
will persist east of the Sierra and down at KMMH.

After a break Tuesday night...another storm system begins to affect
a larger part of the region Wednesday through Thursday. This one
will be stronger with more precipitation, lower snow levels and
gusty winds. Hohmann

&&

.REV Watches/Warnings/Advisories...
NV...Wind Advisory from 8 AM to 10 PM PST Monday NVZ005.

     Lake Wind Advisory from 10 AM to 10 PM PST Monday for Lake Tahoe
     in NVZ002.

     Winter Storm Watch from Wednesday afternoon through late
     Thursday night NVZ002.

     Lake Wind Advisory from 10 AM to 6 PM PST Monday for Pyramid
     Lake in NVZ004.

CA...Wind Advisory from 8 AM to 10 PM PST Monday CAZ070-071.

     Winter Storm Watch from Wednesday afternoon through late
     Thursday night CAZ071.

     Lake Wind Advisory from 10 AM to 10 PM PST Monday for Lake Tahoe
     in CAZ072.

     Winter Storm Watch from Wednesday afternoon through late
     Thursday night CAZ072.

&&

$$

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


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