Area Forecast Discussion
Issued by NWS Reno, NV
FXUS65 KREV 250953
Area Forecast Discussion
National Weather Service Reno NV
253 AM PDT Tue Oct 25 2016
Showers across the Sierra will diminish through this afternoon with
lighter winds and drier conditions expected through mid week.
Confidence continues to increase for a warm and wet system by late
Thursday into Friday with yet another storm possible Sunday.
A light band of rain showers continues across the northern Sierra
this morning with shadowing keeping the bulk of the activity on the
west slopes. Snow levels remain high and generally in the 7,500-
8,000` range across the central Sierra with mainly just wet roadways
evident on roadway cams through the Sierra. These showers will
dissipate through the day today with only some light shower activity
remaining mainly across western Lassen County through early
Gusty winds along the ridges will also diminish through the afternoon
as an upper level ridge builds across the Continental Divide leaving
us with a drier southwesterly flow aloft for the next few days.
Winds will be lighter over the next few days but winds along the
ridges will stay breezy through Wednesday and then pick up again on
Thursday as our next low pressure system arrives.
An upper low over the Gulf of Alaska will rotate another shortwave
trough across the western U.S. by Thursday which will tap into
subtropical moisture and provide chances for a period of moderate to
heavy rainfall for the Sierra and western Nevada as early as
The warm subtropical trajectory of this system will result in very
high snow levels (~10,000`) and will likely be mostly a rain maker
except for the very highest peaks. The biggest uncertainty at this
time continues to be with timing the initial wave of precipitation
as the EC continues to bring rainfall in Thursday evening with the
GFS starting early Friday morning. The EC has maintained consistency
with its timing and the GFS ensembles actual favor more towards the
EC deterministic run. As such, continued to side with the EC
solution with Sierra rainfall beginning Thursday evening with the
bulk of the precipitation occurring through Friday morning. Overall,
precipitation amounts are lower end confidence at this points but
with our recent wet pattern additional rises on creeks and streams
are possible Thursday night and Friday. Fuentes
.LONG TERM...Friday through Monday...
Low pressure system will continue to affect our region through
Friday with widespread wetting rains and high elevation snowfall.
Snow levels look to remain above 9500 feet for the duration of the
event, so looking at only minimal issues from snow. The bigger
concern will definitely be areas of moderate to heavy rainfall,
where some locations in the Eastern Sierra could see 1-2" of
rainfall total for this storm.
The latest runs of the GFS are showing a secondary shortwave moving
across Northern CA immediately after the main trough passage on
Friday. In this solution, the the heavier precip could shift north
for Lassen/Plumas through Friday night and into Saturday. This is a
newer development, so we`ve only slightly increased chances for
precip in the Northern Sierra for Friday night, but will need to
continue to monitor this change as it could significantly increase
the amount of QPF north of Tahoe.
The active weather pattern continues into the weekend, as another
disturbance moving in either late Saturday or Sunday morning. Models
are a bit off on the timing, so this leads to some uncertainty as to
when the peak precipitation will arrive. However, models have been
consistent showing in this storm over the last several days, so
forecaster confidence is high that we will see another storm system
for the weekend. This storm looks a bit colder with snow levels
starting around 8500 feet on Saturday, then falling to near 6500
feet by Sunday night. Winter impacts to the Sierra and Tahoe area
passes are possible on Sunday, anyone with travel plans should pay
close attention to the forecast for Sunday. With the jet diving down
south of Tahoe, we could see spillover into northwestern NV as well.
Even more shortwave troughs are lined up for next week, although
potentially weaker as flat ridging tries to establish over the
eastern Pacific. There is still much uncertainty beyond Monday, but
it does look like areas with the best chances of precip next week
should be mainly north of Highway 50. Hoon
Rain and high elevation snow continues for the Northern Sierra and
Northeastern CA this morning. Around Tahoe, some light rain showers
and MVFR conditions are possible through this afternoon. Mountain
obscuration, icing, mountain turbulence and breezy winds are also
expected for today.
Sierra ridges will continue to gust around 75kt, with low level wind
shear possible at area terminals this morning. Winds will weaken a
bit through the day, although still breezy with gusts up to 25kt.
Improving conditions are expected tonight and into Wednesday. Hoon
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