High Wind in Nevada, November 13, 2020

Area Forecast Discussion
National Weather Service Reno NV
250 PM PST Thu Nov 12 2020

.SYNOPSIS...

A Pacific storm will move through the region Friday into early
Saturday generating gusty to very strong winds with a quick burst
of mountain snow and light valley rain. Temperatures will remain
below average through Saturday, then rise a few degrees above
average next week. A pause in storm activity is likely before
another storm system moves in for the middle of next week.

&&

.SHORT TERM...

Updates this forecast cycle:

*Upgraded Wind Advisory to a High Wind Warning for the Greater
 Lake Tahoe area and the Reno-Carson City-Minden area from 10 am
 Friday to 1 am Saturday.

*Issued a Special Weather Statement for the Tahoe Basin regarding
 the quick burst of heavy, wet snow expected for Friday into
 early Saturday morning.

Taking a look out the window this afternoon, tranquil weather
conditions are occurring with scattered cirrus clouds, a light
southwest breeze, and temperatures in the 40s. A bit scuzzy in
the Truckee Meadows this afternoon with surface inversions still
in place thanks to light winds and minimal mixing. Another
indication of the strong/shallow valley inversion in place is
that the airplane noise has been noticeably loud this afternoon,
getting trapped in the valley. However, these conditions will not
last long as the pattern becomes active once again starting
tomorrow.

A quick, but strong Pacific storm is on tap to make impacts to the
region for Friday into early Saturday. The strong southwest winds
will be the main issue with this system across the region with
some mountain snow and light valley rain expected during this
time.

Winds: It's going to be windy region-wide Friday into Friday
night. That pretty much sums it up. Details you ask? Forecaster
confidence has increased this afternoon in overall intensity of
the southwest winds which has prompted us to upgrade the Wind
Advisory for the Tahoe and Reno-Carson City-Minden areas to a High
Wind Warning. The set up looks to be there for the development of
very strong winds. The placement of the upper-level jet, a stable
layer around 700 mb, and 700 mb winds in the 60-70 kt range (100+
mph Sierra ridge gusts) all suggest strong winds from the Sierra
into the Basin and Range. Another variable that has caught our eye
this afternoon was recent short range model guidance suggesting a
quicker timeframe of impact. Now, the strongest winds look to
happen between 1 pm to 7 pm Friday instead of later in the
evening which would take place during the time period of optimal
mixing. This would allow those stronger 700 mb gusts to mix down
to the surface. Even with these strong winds forecast, we are
still not anticipating a text book down sloping wind event during
this time due to the increase in humidity and moisture. For
specifics on wind speeds and impacts, please see the High Wind
Warning and Wind Advisory products on our website.

Precipitation: Not many changes to the forecast regarding mountain
snow and valley rain. It will be a quick shot of precipitation
starting late Friday morning in northeast California and
eventually spreading into the Tahoe Basin south into Mono County
by the afternoon hours. Total liquid amounts of 0.15-0.50" are
forecast for these areas with up to an inch along the Sierra
crest. Some spillover into western Nevada is expected, but will
be minimal in terms of total amounts with 0.01-0.10" of QPF
possible. Not much if any is forecast for locations along and east
of US-95. As for snowfall, not much is expected with this storm
due to the warmer temperatures increasing snow levels coinciding
with the main push of moisture. Zero to 2 inches of wet, heavy
snow is possible around the lower elevations in the Tahoe Basin
with up to 6 inches along the Sierra crest. Even though snow
amounts will be limited, hazardous travel is likely Friday through
early Saturday morning along the Sierra passes (I-80 & Carson
Pass). Remember, it does not take a lot of snow to cause
visibility reductions when winds are very strong.

The precipitation and winds taper by Saturday morning (after 4 am)
across the region. Breezy west-northwest remain for Saturday with
some showers along the Oregon border into early Sunday.
Temperatures remain just below average with an increasing trend
anticipated Sunday into next week. -LaGuardia

.LONG TERM...Sunday onward...

A few light showers continue Sunday morning near the Oregon border,
but the overall pattern will be warming and drying into next week as
ridging builds over CA/NV. Temperatures will creep up to about 10
degrees above normal, into the mid 60s for western Nevada upper 50s
in the Sierra Monday and Tuesday. The next trough will move into the
West Coast late Tuesday into Wednesday, bringing our next round of
precip, gusty winds, and cooler temperatures beyond Thursday.

Latest trends continue to slow down this system to Wednesday,
possibly even into Wednesday night and Thursday. This storm system
looks to bring a decent shot of precipitation for the Sierra,
although it should move through rather quickly so it won't hang
around too long to drop heavy precipitation. At this time, precip
amounts have a lot of variation in the ensembles, but most likely
storm totals from Tuesday night through Thursday will be around 0.25-
0.75" in the Sierra with less than 0.20" along the lower elevations
of northeast California and western Nevada. With snow levels
remaining above 8000ft, only the highest elevations will see a quick
burst of snowfall.

Probably the bigger impact for the region will be the stronger S-SW
wind ahead of the storm system...which will also help to limit the
amount of spillover east of the Sierra and increase the chance for
strong gusty winds. -Hoon

&&

.AVIATION...

Winds aloft and cloud cover will begin to increase tonight ahead
of a Pacific storm system with strong southwest winds the main
concern on Friday. Significant mountain wave turbulence and
periods of wind shear are likely Friday into early Saturday
across the region. Surface wind gusts could exceed 40-50 kts
Friday and Friday night.

The storm arrives Friday lasting into early Saturday, with the
worst conditions likely to be Friday and Friday night. Periods of
MVFR with isolated IFR conditions can be expected for the Sierra
by Friday afternoon into Saturday morning along with widespread
terrain obscuration. The bulk of the precipitation is likely to
push into the region after 10 am Friday, lasting through around 4
am Saturday. Precipitation is likely to be rain at all terminal
sites, although a rain-snow mix is possible for Sierra terminals
at the onset of Friday morning before the warmer air arrives. Any
accumulation would be slush and should quickly melt off. Light
rain is possible into western Nevada, but the area will remain
shadowed for the most part. Breezy west-northwest winds remain for
Saturday with a few lingering showers near the Oregon border on
Sunday. -LaGuardia/Dawn

&&

.REV Watches/Warnings/Advisories...

NV...High Wind Warning from 10 AM Friday to 1 AM PST Saturday
     NVZ002-003-005.

     Wind Advisory from 10 AM Friday to 1 AM PST Saturday NVZ001-004.

CA...High Wind Warning from 10 AM Friday to 1 AM PST Saturday
     CAZ070>072.

     Wind Advisory from 10 AM Friday to 1 AM PST Saturday CAZ073.

&&

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