Area Forecast Discussion
Issued by NWS Reno, NV

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

953
FXUS65 KREV 202132
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
232 PM PDT Wed Sep 20 2017

.SYNOPSIS...

A strong cold front will bring windy conditions through tonight
and at higher elevations up to a few inches of snow. Showers are
possible across the region with snow levels falling to around
seven thousand feet by Thursday morning. Temperatures will remain
below normal through the weekend and may drop below freezing in
some lower elevation valleys starting Friday night. Next week is
likely to be dry with a slow warming trend.

&&

.SHORT TERM...

Expect RAPIDLY CHANGING WINTER CONDITIONS at higher elevations
in the Sierra tonight and at higher passes in NE California,
the Tahoe Basin, and eastern Sierra, including Donner Pass on
I-80 and on the Mount Rose highway above 8,000 feet. This is not a
big snow storm by any means (a few inches above 8,000 feet) but
anyone traveling over mountain passes or hiking in the higher
elevations will need to be prepared.

A cold front moving south across northern CA this afternoon will
sweep across the Tahoe Basin this evening and across Mono/Mineral
counties after midnight. Prefrontal wind gusts 30-40 mph (higher
in wind prone locations) and ridge gusts 70-90 mph are occurring
this afternoon and will continue through the evening, and then
shift to the west/northwest and slowly decrease overnight post
frontal. Lake winds will continue to increase this
afternoon/evening with very choppy conditions on area lakes. Small
boats, kayaks and paddle boards on Lake Tahoe or Pyramid lake
will be prone to capsizing through this evening.

New computer simulations show an unstable, saturated layer below
700 mb with the frontal passage. This increases the potential for
several hours of moderate precipitation in the Sierra with the
frontal passage. Snow levels may fall to around 7,500 feet in the
Tahoe Basin/Alpine County by Thursday morning and to around 8,500
feet in Mono County. This will be the first snow event of the
season with a few inches of accumulation possible above 8,000 feet
along with very strong winds. These will be DANGEROUS CONDITIONS
for hikers, campers or anyone exposed to the weather at those
higher elevations.

At lower elevations, rainfall amounts should generally be less
than 0.10 inches, but areas near the Oregon border and higher
terrain east of US-95 could see higher amounts, perhaps 0.25 to
0.50 inches by Thursday morning.

For Thursday, a secondary shortwave moving across the Sierra
could trigger bands of showers spreading across the Sierra and
parts of western NV. Stronger showers could create snow grains
which could briefly create slick roadways before melting,
including downstream of Pyramid Lake Thursday afternoon along I-80
between Sparks and Fernley.

By Thursday night and Friday, shower coverage will decrease as
forcing becomes weaker. Lows could drop into the 30s as soon as
Friday morning for colder valleys with some freezes possible if
sufficient breaks in the cloud cover occur. The potential for
freezing temperatures or even a hard freeze will increase each
night this weekend across more valley areas as drier air spreads
over the region with light winds prevailing. This could be the
FIRST SOLID FROST/FREEZE EPISODE of the fall season, with
potential impacts to irrigation and vegetation. For any home
gardeners who still have sensitive vegetation growing, check your
local temperature forecast. If the forecast low is 40 degrees or
below, you run the risk of seeing frost as surface temperatures
can often be several degrees colder than the official forecast
lows at approximately 6 feet off the ground. JCM

.LONG TERM...Monday through Wednesday...

A highly amplified ridge begins to expand across the eastern
Pacific over the weekend and is expected to shift into the west
early next week. This will bring dry conditions and warming
temperatures for at least the first part of the next work week,
possibly back into the 80s in western NV by midweek. JCM

&&

.AVIATION...

A cold front is moving south across the Sierra and western NV this
afternoon through tonight as an upper level trough shifts south
into the Great Basin. Widespread surface gusts are reaching 30-40
kts with 40+ kts in wind-prone areas. Ridge wind gusts are blowing
in excess of 70 kts through at least midnight. Showers are
spreading southward out of NE CA this evening and tonight leading
to lowered cigs and mountain obscuration. Expect widespread
turbulence along and east of the Sierra front with areas of
localized low-level wind shear.

Winds should decrease late tonight into Thursday morning.
Attention then turns to unsettled weather beneath the upper level
trough. Rain and higher elevation snow showers will continue to
spread across the area from northwest to southeast Thursday, with
lowering CIGs and VIS at times. JCM

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 9 PM PDT this evening for Pyramid Lake
     in NVZ004.

     Lake Wind Advisory until 9 PM PDT this evening for Lake Tahoe in
     NVZ002.

CA...Lake Wind Advisory until 9 PM PDT this evening for Lake Tahoe in
     CAZ072.

&&

$$

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.