Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 171340
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
540 AM PST Sun Feb 17 2019

.UPDATE...

Update this morning to extend the current Winter Storm Warnings
in the Sierra through this evening and also to issue a Winter
Weather Advisory for Sierra Front valleys including Reno/Sparks,
Carson City, and Carson Valley through this evening.

The next wave of snow is beginning to impact the Sierra and the
Hwy 395/I580 corridor from the North Valleys through Reno and into
Douglas county. A cold and unstable airmass will allow for
widespread snow shower activity today. The core of the low will
move aloft this afternoon and will allow upper level deformation
forcing to set up across the northern Sierra through Reno and into
the Carson Valley. Latest hi-res models are targeting a heavier
banded area of snowfall. Some disagreement still exists on the
exact placement of the band but generally along the Sierra Front
corridor. This combined with a favorable environment for lake
effect snowfall off of Lake Tahoe may produce localized amounts
of higher snowfall particularly through the Carson Range and
Washoe Valley through the Carson Valley. Some enhancement is also
possible through South Lake Tahoe as winds begin to shift
northerly through the afternoon.

Cold surface temperatures are allowing snow to easily stick on
road surfaces and temperatures are not expected to warm much above
freezing across many valleys today. Hazardous driving conditions
are expected particularly through the Sierra where conditions have
been poor for travel over the past few days. Travel is not
advised. Fuentes


&&

.AVIATION...Updated

A band of snow has moved into the Tahoe Basin and Sierra Front
this morning. For KRNO/KCXP, expect MVFR and IFR conditions
through 18Z with runway accumulation around an inch for KRNO and
up to 3 inches for KCXP.

Sierra terminals, no significant changes except to speed up timing
for the snow into KMMH with a more steady snow expected. X


&&

.PREVIOUS DISCUSSION... /Issued 237 AM PST Sun Feb 17 2019/

SYNOPSIS...

Periods of moderate to heavy snowfall continue in the Sierra today
with scattered snow showers expected across western Nevada. Travel
will be difficult in the Sierra where long delays are likely to
continue. Some lake effect snows are possible near Tahoe and
Pyramid. Frigid overnight lows are expected early next week with
subzero temperatures possible for some Sierra valleys. The next
round of snowfall looks to arrive midweek as a slider type system
is possible across the Sierra and western Nevada.

SHORT TERM...

Another day and another wave of snowfall is expected today across
the Sierra and western Nevada. Snow showers will pick up in
coverage/intensity this morning and persist into the afternoon.

Widespread low-mid level instability will be in place today as
the cold core of a shortwave moves directly overhead. This will
result in snow being showery in nature and more widespread in
coverage. However, the presence of this instability and forcing
will allow for smaller, localized areas where pockets of heavier
snow accumulations are possible. Where would these pockets be you
ask? Well, potential areas would be along S-SE locations downwind
of Lake Tahoe and Pyramid lake where the environment is becoming
more favorable for the development of banded lake effect snow.
Areas roughly from I-80/Hwy 50 north also show some potential for
banded snow, not from lake effect, but from deformation forcing
associated with the upper low.

Take home message would be travel will continue to be sketchy as the
showery nature of snow can lead to one minute being clear, to the
next having a quick burst of moderate to heavy snow in a passing
snow shower or band. Travel through the Sierra has not been good
much of this week and don`t expect today to be much better either.
As always, check the latest conditions with Caltrans and/or NDOT
if you are deciding to travel.

Snow showers will diminish through the evening and we will then
finally get a short break in the weather through Tuesday before
another round of snow arrives mid-week. See the long term forecast
discussion below for more details.

Temperatures will remain cold with highs about 10-18 degrees
below normal for this time of the year. The cold temperatures
combined with ongoing breezy winds will bring wind chill concerns,
especially for exposed mountain locations. Lows will become quiet
cold as we clear out Monday into Tuesday. Tuesday morning could
see the coldest temperatures as we see more clearing skies and
lows become widespread in the teens across western Nevada with
single digit to below zero temperatures in the Sierra. Fuentes

LONG TERM...Wednesday through next weekend...

No significant changes to the extended forecast this morning with
the general ideas of an inside slider in place. If anything, timing
for the slider is leaning more towards Wednesday night into Thursday
morning. Another storm is possible late in the weekend, but model
divergence is much higher at that range.

For the slider, continued to increase the chance of snow a bit for
Wednesday night/Thursday morning. Focused the increases along the
Sierra Front, Mono County and into Southern Lyon and Western Mineral
Counties. The exact track likely won`t be known for at least a
couple more days, and thus how much snow will fall for any area.
Some areas will not see any or just a skiff at best as is typical
for sliders. For very preliminary amounts, think of valley locations
seeing up to 2 inches, mountains up to 6, with local amounts to a
foot in Mono County.

On the back side of the slider Thursday into Thursday night, Mono
County will continue to be favored in the north to northeast upslope
flow. Expect showers to be somewhat numerous south of Highway 50
Thursday before rapidly diminishing overnight except in upslope
areas.

A break is expected Friday into Saturday with temperatures remaining
cold, but starting a slow warming trend. The next storm tries to
drop south coupled with a weak undercut of the East Pacific ridge.
How this comes together will determine if this storm makes it south
of the Oregon border, but ensembles are leaning toward at least a
part of it doing so. Will go with the ensembles, but things will
likely change quite a bit. The models will likely struggle a bit
with the undercut as they often do, and a potential strong typhoon
in the West Pacific doesn`t help matters either. X

AVIATION...

Snow showers to continue in the Sierra and occasionally spilling
over into western NV. Mainly VFR currently, but conditions will
deteriorate this morning, especially in the Sierra. Winds remain
gusty on the ridges for some mtn wave turbulence, but no significant
LLWS is expected the next 48 hours.

KTRK/KTVL: -SHSN to increase with MVFR and IFR conditions through
21Z. Afterward, periods of VFR with occasional IFR in heavier -SHSN.
All snow showers are expected to dissipate after 06Z. Additional
runway accumulation of 2-4 inches expected. Winds will be up to 15
kts, diminishing overnight into Monday.

KCXP: VFR mixed with periods of IFR as lake effect/enhancement off
Tahoe continues through 18Z. Runway accumulation up to 2 inches. A
more consistent band of -SHSN is possible after 18Z as the last wave
of this storm moves through. 40% chance of it doing so, and more
MVFR/IFR conditions would occur until 02Z. All showers expected to
diminish by 05Z.

KMMH: Mainly VFR through 16Z, then periods of MVFR CIGS/VIS in -SHSN
through 07Z. Winds will continue to be gusty, but will become more
WNW after 23Z.

KRNO: VFR through 18Z, then occasional MVFR CIGS/VIS in -SHSN.
Similar to KCXP, there is a 30-40% chance of MVFR being predominant
through 00Z. No runway accumulation is expected due to insolation
and mild runway temps. All showers to clear by 02Z. X

&&

.REV Watches/Warnings/Advisories...
NV...Winter Storm Warning until noon PST today NVZ002.

     Winter Weather Advisory until 7 PM PST this evening NVZ003.

CA...Winter Storm Warning until noon PST today CAZ071.

     Winter Storm Warning until noon PST today CAZ073.

     Winter Storm Warning until noon PST today CAZ072.

&&

$$

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


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