Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 122114

Area Forecast Discussion
National Weather Service Reno NV
214 PM PDT Mon Mar 12 2018


A series of winter storms will produce unsettled conditions
through the upcoming week. The first storm will bring gusty
winds, rain and snow Tuesday into Wednesday. A colder storm is
becoming more likely from Thursday into Saturday, producing
additional periods of heavy snow in the Sierra with some snow
accumulation also possible for lower elevations.



Main change for the short term is upgrading the Tahoe zone to a
Winter Storm Warning as travel impacts will be more significant
over the Sierra passes from mid-afternoon Tuesday through
Wednesday morning. We increased snowfall amounts for the CA side
of the Tahoe zone for up to 2 feet above 7000 feet along the
crest, and around 1 foot below 7000 feet near and west of Highway
89 by Wednesday morning. The NV side of the Tahoe zone is not
expected to receive as much snow (roughly half of the CA side) but
we`ll highlight the snowfall differences in the warning text.

Otherwise, we will keep advisories going for northeast CA and
Mono County (best snow potential from US-395 westward in both
areas), where snow totals are not expected to be as large. Still,
the main takeaways are to expect a rapid worsening of conditions
by mid-late Tuesday afternoon as snow levels drop from around 8000
feet to near 6000-6500 feet, as precip initially near the crest
pushes farther east. For Tuesday night, travel in the Sierra and
higher elevations of northeast CA will be hazardous with periods
of heavy snow and poor visibility.

Other highlights/impacts of this storm include:

Winds...Gusts increasing to 35-45 mph across much of western NV by
Tuesday afternoon, with the strongest winds shifting to areas
south of US-50 by Tuesday evening. Sierra ridge gusts could reach
80-90 mph. We will include a Lake Wind Advisory for Pyramid Lake
for Tuesday afternoon through dusk.

Thunder...A few thunderstorms could develop in northwest NV and
the West Central NV Basin and Range Tuesday afternoon/early evening
as daytime heating well into the 60s (possibly reaching 70 in a
few sites) will produce some instability with steep mid level
lapse rates expected in advance of a cold front.

Lower elevation rain/snow...Snow levels will drop by late Tuesday
night for northwest NV and early Wednesday morning across western
NV mainly west of US-95. The post-frontal air mass is not very
cold, so even though snow may fall down to near 4500-5000 feet,
accumulation is unlikely on paved surfaces below 5000 feet. Above
5000 feet, up to 2" of snow could accumulate early Wednesday with
patchy slush possible on roads. Precipitation amounts in Western
NV will generally be light--less than 0.25" except in Douglas
County and from Fallon-Lovelock eastward where some of these areas
could receive up to 0.50 inch.

A short break in the precip Wednesday morning looks to be followed
by a secondary shortwave during the afternoon and evening.
Additional light to moderate snow could fall in the eastern Sierra
and northeast CA, with a light rain-snow mix spreading into
Western NV. The track of this wave varies among the model
guidance, with some scenarios favoring areas from Tahoe northward,
while others bring better precip chances farther south for Mono
County. Overall, some travel impacts are likely in the Sierra and
possibly into foothill locations by early Wednesday evening, while
for lower valleys there is less potential for snow accumulating
or freezing on roads through Wednesday night. MJD

.LONG TERM...Thursday through Monday...

The focus continues to be on the wet weather through Friday night.
More good news this afternoon...the models are coming into better
agreement with a potent system sometime Thursday into Saturday
morning. While there is now high confidence that we will see some
heavy snow in the mountains and possibly into Western NV, the timing
remains fuzzy.

The GFS shows it beginning Thursday afternoon with it lasting
through the day Friday with heavy snow into the Sierra Front of
Western NV. The EC delays it 12 hours while the NAM is in between.
Also, the GFS shows rather heavy amounts as it keeps it pivoting
over the I-80/Highway 50 corridors. The GFS seems a worst case
scenario, so will lean more toward an EC idea for amounts, but blend
the timing. Looking like another 2+ feet in the higher elevations of
the Sierra above 7000 feet with significant accumulations in the
lower elevations more likely. At this point, expect poor travel
conditions anytime from Thursday into Saturday morning, especially
in the mountains.

Over the weekend, the low only slowly pulls away. Instability snow
showers are likely Saturday and possibly into Sunday. With it being
mid-March, thunderstorms are possible near the Sierra Crest and also
in the Basin and Range. I have not put them in the official forecast
yet, but it may be added in the near future.

Monday looks drier, but the GFS is showing another system dropping
off the coast while the EC is farther west. While either is
plausible, I am leaning toward the EC which makes sense due to the
upstream pattern (more amplified ridge with an AR on the west
side) and time of year. Thus, I am showing a bit of a break as
there will likely be a 24-48 hour period of drying out before the
next trough moves in. X



VFR through 18Z Tuesday with increasing winds overnight. South
winds aloft will increase, but expect the valleys to take a little
longer which could result in LLWS (speed, not cross winds) for
terminals after 08-09Z. Regardless, mtn wave turbulence will
occur tonight through Tuesday night. Any LLWS will diminish by 18Z
Tue as the valleys mix out.

Precip then moves in after 18Z Tue with IFR conds in the Sierra
through at least 12Z Wed due to RA changing to SN. Runway
accumulation of up to 6" at KTRK, KTVL and KMMH likely. A brief
period of MVFR CIGS during -RA in KRNO/KCXP/KMEV 00-06Z Wed.
Improving conditions Wed, at least for the lower elevation
terminals, but more IFR conditions are likely late Thursday into
Friday as another potent wave moves through. X


.REV Watches/Warnings/Advisories...
NV...Winter Storm Warning from 1 PM Tuesday to 11 AM PDT Wednesday

     Lake Wind Advisory from noon to 7 PM PDT Tuesday for Pyramid
     Lake in NVZ004.

CA...Winter Weather Advisory from 1 PM Tuesday to 11 AM PDT Wednesday

     Winter Weather Advisory from 1 PM Tuesday to 11 AM PDT Wednesday

     Winter Storm Warning from 1 PM Tuesday to 11 AM PDT Wednesday



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