Lake Wind Advisory 58, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
347 AM PDT Tue Oct 19 2021

.SYNOPSIS...

Rain, mountain snow, and gusty winds return late Tuesday into
Wednesday as the active weather pattern continues. More impactful
storms are forecast to move through the region Friday through the
weekend with potential for strong winds, rain, and heavy mountain
snow.

&&

.SHORT TERM...

The next storm system will push a cold front through the region
Tuesday night into early Wednesday. Southerly flow ahead of this
system paired with the cold core of the low across the PacNW will
result in snow levels near and above 5500 ft. Plan on a period of
gusty winds along with rain and high elevation snow showers. The
storm quickly exits the region on Wednesday, but significant
moisture along with westerly flow will maintain light upslope
showers for the western slopes and the Dixie Fire burn area
possibly into midday Thursday.

Winds... South-southwest winds will increase late tonight into
Wednesday morning, especially for areas north of Highway 50. South-
southwest winds will elevate wind gusts into the 30-45 mph range for
the Sierra valleys and across western NV. Sierra ridge gusts may be
80+ mph. Expect some restrictions to travel for high profile
vehicles, choppy lake conditions, and some aviation turbulence in
and out of the region late tonight into early Wednesday.

Sierra Snow... Although this system isn't quite as cold as the one
from Monday, it will likely provide another round of meaningful snow
to the Sierra. Plan on another period of travel impacts in the
Sierra. The snow potential is targeted for areas north of Ebbetts
Pass (CA-4) with only a few showers possible for the Mono County
crest at this time. Simulations favor 2-3 inches over the Sierra
passes with a dusting to an inch or two for elevations down to 5500
feet or so. In the wetter scenarios, 3-6 inches of snow are possible
above 6000 feet. Be prepared for Sierra travel delays Wednesday AM.

Rain/snow potential across western NV... Southerly flow ahead of
this system may limit spillover into western NV. We could see a
short period of rain early Wednesday morning with coupled upper
jet/surface front dynamics, probably just before or during the
morning commute. Precipitation totals will be light and less than
0.10 inch. Any potential for very light snow will be limited to
areas above 5500-6000 feet in the Virginia Highlands and foothills
along/west of US-395.

Thursday is the 'scheduled break' between systems, but onshore
moisture will still be pushing across the Sierra resulting in
lingering chances for rain and high elevation snow showers
particularly for areas west of Highway 395 and north of Highway
50.

-Edan

.LONG TERM...Friday through next Tuesday...

Two potential Atmospheric Rivers (ARs) this coming weekend into
early next week:

Storm 1 - Friday into Saturday:

* Winds look to increase Friday ahead of an incoming shortwave
  trough and associated weak AR. ECMWF-ENS members are showing much
  of the quasi-geostrophic ascent and cold air advection staying
  north into Oregon, while the GEFS is showing colder air and
  synoptic lift entering the Sierra. Snow amounts will differ
  depending on which solution becomes reality. Most of the snowfall
  should be focused along the higher elevations of northeast
  California. If the GEFS solution does come true (which is a lower
  probability), light snow could fall near Donner and Echo Summit
  (~7000 feet) Friday evening.

Storm 2 - Saturday night into early Tuesday:

* Confidence increasing in a significant AR impacting the West
  Coast, allowing for weak rain shadow to occur (strong spillover)
  into far western Nevada. Deterministic and ensemble model
  guidance are showing a strong signal lining up with idealistic
  conceptual models of strong spillover AR events based upon
  climatology. If model solutions do come to fruition, we could
  see some strong winds, heavy high elevation Sierra cement, and
  moderate-heavy rainfall downwind of the Sierra. Some key
  meteorological elements that are lining up include:(1) Existence
  of a strong mid-level AR delivering moisture to leeside basins
  of the Sierra Nevada; (2) Strong instability owing to weak-
  moderate MUCAPE values of 300-500 J/kg and strong cold air
  advection along the west (windward) side of the Sierra Nevada;
  (3) High-momentum flow with a strong 300-500 hPa jet overhead
  and quasi-geostrophic ascent over the northern Sierra Nevada.

* Disclaimer: We are still 5 days out. In the past, we have seen
  great model agreement days out only to change dramatically as the
  event time nears. Therefore, we could see dramatically altering
  storm impacts if the storm track alters its course. This is
  further reinforced by the large spread in dry versus wet scenarios
  in the ensemble guidance. The weather pattern looks to remain
  active into week two with AR possibilities mainly north of 40
  degrees north latitude.

-Johnston

&&

.AVIATION...

Clear skies and low-level moisture has allowed fog to develop at
KTRK early this morning. Fog should thin out and clear between 16-
18z this morning. Otherwise VFR conditions and light winds for
Sierra and western NV terminals this morning.

The next in a series of storms will migrate into the region late
tonight through Wednesday with mountain wave turbulence increasing
by this afternoon. Winds with this system should peak tonight and
early Wednesday AM as the cold front pushes across the Sierra. There
may be a period of enhanced south winds at KRNO around 12z
Wednesday, a known direction to increase LLWS potential. Rain, snow,
MVFR conditions, and mountain obscurations will also push through
the northern Sierra with snow/freezing levels near 5500-6000 ft msl.
Some light rain may cross into western NV Wednesday AM. -Edan

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

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