Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 162157

Area Forecast Discussion
National Weather Service Reno NV
257 PM PDT Tue May 16 2017


Low pressure will bring gusty winds tonight with periods of light
rain and mountain snow, followed by drier conditions Wednesday
through Saturday. Temperatures will remain below average through
Wednesday, followed by a warming trend. A few late afternoon
thunderstorms may form near the Sierra Sunday through early next



A vigorous upper low over western Washington will slide into
eastern Oregon and Idaho tonight. This will push a cold front
through northeast CA and the northern half of Nevada this evening
and overnight. Intensifying thermal gradients ahead of the
approaching front have brought an increase in winds today, with
gusts currently between 25-35 mph for many areas near and north of
Highway 50. Although cloud cover is likely restraining higher
winds so far today, winds are expected to increase further later
this afternoon and into the evening as the front nears. In fact,
the highest wind gusts could be with a brief burst around FROPA
(after dark for western NV). Therefore, the wind advisories will
be left in place through tonight with winds not falling off
significantly until late tonight behind the front. With the mixed
up conditions tonight, freezing temperatures are not expected for
most lower valleys...with the possible exception of the Surprise
Valley where temperatures could bottom out near 32 Wednesday

As far as precipitation ahead of and with the cold front, upper
forcing will be strongest near/north of the Nevada/Oregon/Idaho
border. Also, the front will be jamming through western NV and
northeast CA rather rapidly tonight. Therefore, most of the
region near/south of an Eagle Lake-Gerlach-Lovelock line and east
of the Sierra crest should see only a quick shot of light
precipitation with the front, with higher amounts up to 0.50" in
the Surprise Valley (better forcing). Higher precipitation
numbers (between 0.20" to 0.50") are possible near the Sierra
crest and west of Susanville where orographic ascent somewhat
replaces the lack of upper support with the cold front.

As far as snowfall totals in the high Sierra, a few inches will
be possible above 7000-7500 feet with some slick high Sierra
passes likely overnight. For I-80 and Highway 50, there could be a
brief window after midnight where a light slushy accumulation
occurs during the tail end of the frontal precipitation. However,
even IF accumulation occurs on I-80/Hwy 50, it is likely to melt
off by around sunrise with marginally cold road temperatures and a
rapid shutoff to precipitation by then.

Precipitation is expected to cut off rapidly behind the front,
with the main story for Wednesday being cool northerly flow and
well below average temperatures. Wednesday night is likely to be
the coolest night of the week for most lower valleys with calmer
conditions and a drying airmass. Colder lower valleys, including
but not limited to the Carson Valley, the North Valleys of Reno,
and the Sierra Valley may bottom out between 28-32...with mid 30s
to around 40 for urbanized areas. Take precautions for Wednesday
night if you have sensitive outdoor vegetation, especially as
temperatures near the ground can be several degrees colder than
the forecast low temperature (typically taken at about 6 feet
above the ground).

Thursday will feature warming with much less chance for lower
valley freezes Thursday night as compared to Wednesday night.

.LONG TERM...Friday and beyond...

On Friday the ridge of high pressure building in the eastern Pacific
will widen enough for the eastern edge of the ridge to move over the
southwest U.S. This will allow warmer air to begin to move into the
region going into the weekend. A weak trough is expected to move
through the Pacific Northwest and into the Great Basin Saturday
helping to keep the ridge from building directly over the Sierra.

With the high pressure building along the west coast, temperatures
in the region will climb to around 5-8 degrees above average through
the weekend. By the beginning of next week we could see a day or two
with temperatures 10 degrees or more above average. By Sunday there
will be potential for some thunderstorms to form along the Sierra
crest with significant daytime heating and projections of a weak
shortwave moving through the flow.

Progressive flow and weak low pressure systems in the Eastern
Pacific should de-amplify the ridge as it moves over the Western
U.S. next week. This should keep the region from going into an
extended period with temperatures significantly above average.



A cold front will move through the region late this afternoon
through tonight. For the rest of the afternoon a few light showers
and increasing winds will continue ahead of the front. As the front
approaches this evening a band of rain and mountain snow will move
through the region. Winds will increase along the front with gusts
up to 35-40 kts. 100 kt jet stream over the region will continue to
create areas of light to moderate turbulence and low level rotors. A
rotor is currently affecting KRNO with light east surface winds and
mountain top winds SSW gusting to 70 mph.

CIG/VIS restrictions and mountain obscuration should be expected in
the Sierra tonight.  With a strong gradient in place winds will
remain breezy overnight. Wednesday through the weekend high pressure
will build into the area with drier conditions, warming temperatures,
and light winds. -Zach


.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 5 AM PDT Wednesday for Pyramid Lake in

     Wind Advisory until 5 AM PDT Wednesday NVZ003.

     Wind Advisory until 11 PM PDT Tuesday NVZ005.

     Lake Wind Advisory until 5 AM PDT Wednesday for Lake Tahoe in

CA...Wind Advisory until 11 PM PDT Tuesday CAZ070.

     Lake Wind Advisory until 5 AM PDT Wednesday for Lake Tahoe in



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