Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 142300
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
300 PM PST Tue Nov 14 2017

.SYNOPSIS...

A strong atmospheric river storm will impact the region Wednesday
into Thursday. Strong damaging winds are expected Wednesday
afternoon across western Nevada with high fire danger. Heavy rain
and mountain snow will arrive Wednesday into Thursday in the
Sierra with high snow levels. A cold front will drop snow levels
Wednesday night into Thursday and will provide spillover rainfall
across western Nevada.

&&

.SHORT TERM...

A strong Atmospheric River (AR) storm is expected to move in
Wednesday and Thursday. This storm will be the strongest of the
fall season so far, in terms of winds and precipitation. Winds
will increase Wednesday morning ahead as the leading edge of the
storm moves into northern CA/NV. Cold front will move through
Wednesday evening into Thursday morning, lowering snow levels and
bringing heavy spillover into the western Nevada and northeastern
CA valleys.

Update summary to the forecast this afternoon:

* Very strong damaging winds forecast for the Sierra Front and
  Highway 395/Interstate 580 corridor. High wind warnings are in
  place for Wednesday afternoon through Thursday morning.

* High winds and dry vegetation along the Western Nevada Sierra
  Front, West-Central Nevada, and the Eastern Sierra in Mono
  County will lead to critical fire weather conditions. Red Flag
  Warnings have been issued for Wednesday.

* Storm continues to look warmer and wetter, so we have increased
  precipitation totals. Heavy snow totals are still expected for
  the High Sierra. Winter Storm Warnings have been issued for the
  Sierra zones, for heavy snow in the high elevations and high
  winds.

TIMING:

Wind: Strongest winds are expected Wednesday afternoon and
evening and will decrease briefly for Thursday morning. Wind gusts
of 55-70 mph will be widespread mainly from the Carson Valley
through Reno and into northern Washoe County. Wind prone locations
could see localized 70+ mph gusts. Aviation impacts expected
along with road restrictions for high profile vehicles. Blowing
dust will be a concern for areas east of Reno, especially for
Churchill, Pershing, and Mineral counties. High winds will also
lead to critical fire weather conditions for the lower elevations
along and east of Highway 395 where dry vegetation still exists.

Precipitation: Moderate to heavy rainfall arriving my mid-
afternoon Wednesday in the northern Sierra and Tahoe Basin with
the peak intensity occurring from late afternoon through Thursday
morning. Heavier precipitation won`t arrive in Mono County until
Wednesday evening. Spillover rainfall for western Nevada will
arrive with the front probably after midnight and will persist
into early Thursday morning.

PRECIPITATION:

Tahoe Basin & Northeast CA:
Liquid totals through Thursday evening look solidly in the 3-4"
range with up to 5"+ right along the Sierra crest. Heaviest
snowfall will generally remain above 8,000 feet where 2-3 feet of
heavy wet snow is possible. Localized areas of 4`+ are possible
right along the Sierra Crest. Snow levels should begin to fall
after midnight Wednesday night at which point winter travel
impacts may begin on the passes. Snow levels are hanging up for a
longer period of time and may not fall all the way to Lake Tahoe
level until Thursday evening, with a few inches of snow Thursday
night into Friday morning.

Mono County:
Liquid totals through Thursday evening look similar and in the
2-4"+ range. Snow levels will be a bit higher and in the
8,000-8,500` range. Snow totals in the high Sierra over 8000 feet
will be around 2-3 feet with localized areas up to 3`+ along the
Sierra Crest. Precipitation totals are lower confidence in Mono
County however as some model guidance were showing a longer
duration of heavier precipitation. Latest runs do seem to have
Tahoe and the northern Sierra in the bullseye, but this could
easily shift further south into Mono County.

Western Nevada:
Spillover rainfall looks to occur in about a 6 hour window roughly
after midnight Wednesday night into Thursday morning through about
the I-80/Hwy 50 corridor before the front pushes south through the
region Thursday morning. Rainfall amounts of 0.50"-1.5" are
possible through the Hwy 395/I-580 corridor with amounts closer to
0.25" across the Basin and Range including areas such as Lovelock
and Fallon. Fuentes/Hoon

.LONG TERM...Friday through early next week

The midweek storm is expected to exit western NV by the end of the
week, although some leftover rain and snow showers are possible
Friday morning, with snow levels down near 4500 feet. For the
remainder of Friday into Saturday, a flat ridge will keep dry
conditions with areas of high clouds over the region, with highs a
few degrees below average Friday then trending warmer going into the
weekend.

Another Pacific storm system is then projected to reach the eastern
Sierra by the Sunday-Monday time frame. This storm currently looks
to be on the warm side with snow levels likely remaining above 8000
feet. The latest guidance is also trending toward a split trough,
but disagrees on whether the split occurs before or after this
trough moves inland. The offshore splitting scenario would keep most
precip limited to the Sierra, while the inland scenario would
potentially bring a short period of rain to lower elevations of
western NV. The longwave pattern downstream seems to be favoring the
ridge prevailing between the Rockies and the central US while a cold
trough digs over the eastern US, which would probably be sufficient
to split the incoming trough before it reaches the Sierra. However,
this is a period of below average forecast confidence due to the
range of possibilities with the track of this trough. At this time,
we will start with better precip chances near the Sierra and
northeast CA, but relatively modest rain chances across western NV
valleys. MJD

&&

.AVIATION...

A powerful storm system begins to affect the Sierra and western
Nevada Wednesday through Thursday. This storm will be the strongest
so far this season with more precipitation, strong winds, and
lowering snow levels by Thursday.

Winds will begin to increase across the mountain tops tonight and
significantly increase further Wednesday. LLWS will be likely by
midday Wednesday as southerly winds develop across valleys and
southwest ridge level winds increase to 55-70 kts with gusts
approaching 90kt. The period from 18Z Wednesday to 06Z Thursday
appears to be the most critical window for wind, especially for the
eastern Sierra along the Highway 395 corridor extending out to Hwy
95. Sustained winds 25-35 kts with gusts to 50 kts will be
widespread and there could even be a period of stronger winds from
Reno south toward KMMH late Wednesday afternoon and evening ahead of
the precipitation band.

Rain will reach the Sierra Wednesday afternoon and will spill over
into western NV along and north of I-80. As this rain band shifts
southward overnight, surface winds will ease although ridge level
winds are going to remain strong and turbulence will persist.
Moderate to occasionally heavy rain in the Tahoe Basin will push
CIGS/VSBY down to MVFR levels Wednesday night into Thursday morning.
This band of rain will shift southward into the eastern Sierra of
Mono County for Thursday with lowering CIGS/VSBY at KMMH. As far as
snowfall, several inches may accumulate at KTRK/KTVL Thursday
morning as snow levels fall. Hohmann/Edan

&&

.REV Watches/Warnings/Advisories...
NV...High Wind Warning from 10 AM Wednesday to 4 AM PST Thursday
     NVZ003-005.

     Red Flag Warning from 10 AM to 7 PM PST Wednesday NVZ450.

     Winter Storm Warning from 4 PM Wednesday to 4 AM PST Friday
     above 7000 feet in NVZ002.

     Red Flag Warning from 10 AM to 7 PM PST Wednesday NVZ453-459.

     Wind Advisory from 10 AM Wednesday to 4 AM PST Thursday
     NVZ001-004.

CA...Winter Storm Warning from 4 PM Wednesday to 4 AM PST Friday
     above 6000 feet in CAZ071.

     High Wind Warning from 10 AM Wednesday to 4 AM PST Thursday
     CAZ070.

     Red Flag Warning from 10 AM to 7 PM PST Wednesday CAZ273.

     Winter Storm Warning from 4 PM Wednesday to 4 AM PST Friday
     above 8000 feet in CAZ073.

     Winter Storm Warning from 4 PM Wednesday to 4 AM PST Friday
     above 7000 feet in CAZ072.

&&

$$

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



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