High Wind in California, January 3 to 4, 2020

Area Forecast Discussion
National Weather Service Reno NV
324 PM PST Fri Jan 3 2020

.SYNOPSIS...

A couple of fast-moving weather systems will bring gusty winds late
tonight and Saturday, and chances for light snow and rain at times
this weekend mainly north of Interstate 80. Cooler temperatures
are expected Sunday through much of next week, with additional
weak weather systems possibly bringing short periods of light snow.

&&

.SHORT TERM...

Abundant mid and high clouds are streaming over the region today
as low pressure approaches the northern CA coast. Above normal
temperatures are expected through Saturday as southwesterly flow
brings warmer temperatures aloft.

Winds increase tonight and into Saturday morning as the weak
shortwave moves through region. We could see a brief period of
gusty winds overnight mainly along the US-395 corridor from Reno-
Carson-Tahoe northward to Susanville with gusts up to 45 mph.
Sierra ridges will increase with gusts up to 80 mph tonight as
well. Lake Tahoe will become choppy tonight and into Saturday so
a Lake Wind Advisory has been issued from 9pm tonight through
Saturday afternoon.

Light rain and snow will move into the northern Sierra and
northeast California tonight and into Saturday morning, bringing a
light coating of snow for elevations above 4500-5500ft in Lassen,
Plumas, and Modoc Counties. Expect to see most locations with up
to an inch or two for those areas, including CA-36, CA-44, and
US-395 north of Susanville. Surprise Valley could also see some
light amounts of snow Saturday morning with up to an inch or so.

Another weaker disturbance moves over the Oregon border Saturday
night into Sunday with meager precipitation for northern Washoe
and Lassen Counties along with breezy conditions Sunday afternoon
(up to 25-30 mph). -Hoon

.LONG TERM...Tuesday through next weekend...

A couple rather moisture-starved disturbances will move down the
east side of a large-scale ridge over the northeast Pacific, the
first one late Tuesday and Tuesday night, with the second one on
Thursday. By next weekend, the pattern begins to shift to allow
cold, wetter, and more potent systems to affect northeast California
and western Nevada. This will be the case as the longwave Pacific
ridge begins to retrograde towards the north-central Pacific and
Aleutian islands and allows storms to utilize more Pacific moisture
and drag in cold air.

As far as details of the system Tuesday, it will be fast-moving and
will push a cold front through the area in the afternoon and evening.
Currently, orographic lift, moisture, and post-frontal instability
look sufficient to bring a very light snowfall to the northern Sierra
and portions of northeast California. Elsewhere, breezy conditions
are likely with the front; however, precipitation is spotty in many
simulations, possibly due to the misalignment of the frontal forcing
with the upper wave (front outrunning forcing). Still, a few snow
showers (little or no snowfall) are possible into far western
Nevada by Tuesday night.

Thursday's system is expected to take a more slider-like track into
northern California and the Sierra. At least two-thirds of EPS
members show a light snowfall for sites around northeast CA and
western NV, with the GEFS also showing a good number of solutions
with a similar idea. Still, details are slim for now given that it
is still day 6 and also due to the sensitivity of track to bringing
accumulating snow with slider systems. Therefore, POP remains
modest for now. In any case, with colder air invading by mid-week
any precipitation Thursday is projected to be all snow.

Next weekend, as mentioned, the pattern begins its shift towards
more significant storms as the large-scale Pacific ridge retrogrades.
The first of these is due in AROUND next Saturday as a cold front
arrives and brings snow above valley floors, with rain changing to
snow for valleys (even lower ones). Also, winds could pick up
substantially ahead of the front next Friday; in fact, winds Friday
could be the strongest of the 7-day period. -Snyder

&&

.CLIMATE...January 13-20...

...Cold and stormy for mid to late January...

Looking beyond the 7-day forecast, GFS and EC ensembles continue to
support longwave ridge retrogression from the northeast Pacific back
towards the Aleutians and Bering Sea by mid-month. This pattern
shift will allow systems to track farther west over the Pacific and
pick up more moisture in contrast to the drier systems expected
through most of next week.

Given the colder flow with a deepening trough over the West downstream
from the ridge, there will be an increasing potential for much more
significant snow events in the Sierra and across northeast California,
possibly working into western Nevada if systems line up just right.
As far as temperatures, the well-supported longwave trough over
the West means there is high confidence in below to well below
average temperatures overall. -Snyder

&&

.AVIATION...

A weak weather system is moving into the region tonight and Saturday
with increasing winds aloft. Surface wind gusts may reach up to
25-35kts, especially for KTRK/KTVL and north to the Oregon border.
Low level wind shear is likely ahead of the front.

Not much precipitation is expected, only a chance of a dusting at
KTRK and KTVL Saturday morning, but some periods of MVFR CIGS may
be possible. Better chances of rain and mountain snow will be north
of KTRK to the Oregon border, including KSVE.

A secondary wave of low pressure could bring another round of
snow showers to the area Sunday. This one would produce snow down
to the lower valley floors; however, it too has limited capacity
for accumulations on area runways. -Hoon

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 9 PM this evening to 4 PM PST Saturday
     for Lake Tahoe in NVZ002.

CA...Lake Wind Advisory from 9 PM this evening to 4 PM PST Saturday
     for Lake Tahoe in CAZ072.

&&

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