000
FXUS65 KREV 302234
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
234 PM PST Mon Jan 30 2023

.SYNOPSIS...

Tonight into Tuesday morning we`ll see continued bitter cold
temperatures. As we move into the beginning of February,
temperatures will gradually swing back towards seasonal averages.
A fast moving cold front will bring a few light snow showers to
the Sierra crest this Friday and with another possible system
Sunday into Monday.

&&

.DISCUSSION...

Today`s highs are struggling to even reach freezing as a bitterly
cold modified arctic airmass spread into the Sierra and western
Nevada. Overnight lows are still expected to drop into frigid
territory with widespread single digit and below zero temps by
daybreak Tuesday morning. The valleys of the eastern Sierra in
Mono County could very well see the coldest low temperatures
dropping into the double digit negative realm. Tuesday highs will
rebound slightly with upper 20s to near freezing for Sierra
Valleys and 30s for most lowers valley areas. Mostly areas will
see more seasonal temperature by mid-week that will level off
through the remainder of the week.

Increasing northeast to east ridge winds tonight across the Sierra
crest will bring dangerous wind chills to exposed areas of the
high Sierra. Wind chills of -20 to -35 will rapidly bring about
frostbite to exposed skin. It may be a good idea to postpone plans
or at least be sure to have proper protective gear.

Inversions will once again strengthen after tonight as high
pressure brings lighter winds and clear skies to region. This will
increase the chances (10-15%) for development of patchy freezing
fog and scattered low status to Sierra valleys and reinforce the
same over the Mono basin. The limited mixing and ventilation could
bring air quality concerns through the week in the valleys,
particularly across more urban areas.

Sierra ridge top winds will increase from the southwest Thursday
into Friday as another Pacific storm taps into a weak fetch of
subtropical moisture. This weaker system will bring increased
chances for light snow showers over northeast California and the
Sierra overnight Thursday through Friday. Blended guidance so far
has a low chance (15-25%) for at least 4-6 inches over Sierra
passes, and an inch or two for Sierra valleys and the Lake Tahoe
basin. Little spillover is expected with this system, but some
areas along the eastern foothills could see a brief period of snow
flurries. A stronger storm system will tap into a deeper and
warmer fetch of moisture as a moderate AR wraps into this storm
system. Improved forcing with this system will bring a better
chance for moderate snow to the Sierra passes overnight Saturday
through Monday. Blended guidance projects a decent chance (20-30%)
for 8-12 inches above 7000 feet and few more inches of
accumulated snow for the Lake Tahoe Basin. This stronger storm
will once again bring increased chances for more travel impacts
late weekend into early next week across the Sierra and northeast
California.

One interesting aspect of the extended ensemble guidance is the
lack of any notable moisture or forcing going into next week.
However, there isn`t any evidence that suggests the appearance of
any longwave blocking pattern setting up any time either.

-Amanda

&&

.AVIATION...

Sierra and western Nevada terminals will for the most part remain
VFR through the forecast period. Some mountain obscurations will
continue along higher terrain along the eastern Sierra into the
evening hours.

East-northeast winds increase across the Sierra crest tonight but
begin to tapper off overnight into Tuesday. Wind gusts across higher
ridges around the Lake Tahoe basin south along the eastern Sierra
will top at 60-70 kts before gradually decreasing through Tuesday
morning. These gusts will increase the chances for some turbulence
and LLWS over Sierra terminals till 12Z. But most turbulence will be
focused more west of the Sierra crest.

With upper ridging building over the region, the lighter winds and
clearing skies will bring more efficient surface cooling that
strengthen inversions over Sierra valleys. Therefore, the Martis and
Sierra valleys do have a low chance(