Scientific Forecaster Discussion
fxus65 krev 221122
Area forecast discussion
National Weather Service Reno Nevada
322 am PST Wed Nov 22 2017
Very mild conditions will prevail through Saturday with a few record
highs possible. Most areas will remain dry although very light
rain is possible Thursday in northeast California and northwest
Nevada. Saturday is expected to be windy ahead of a strong cold
front which will bring snow to the Sierra and northeast California
Sunday and Sunday night. It will be much colder early next week.
Lowered highs a few degrees today, otherwise little change to the
forecast through Friday.
This morning, thinner/higher cloud cover has allowed temperatures
to fall off to at least a few degrees cooler than yesterday at this
time, with Lovelock 10 degrees lower. The cooler start along with
marginal winds aloft (between 15-30 kts at 700 mb) for mixing
should keep highs from warming much today as compared to Tuesday
and, in some cases, highs could actually be slightly cooler. Still,
a couple records are still possible including at the Reno Airport
where the record high is only 69 today.
For Thursday/Thanksgiving day, the upper ridge will flatten a bit
as low pressure moves into the Pacific northwest, while a narrow
band of moisture pushes across northern California and northwest Nevada. The
location of this moisture feed has trended a bit farther south,
possibly reaching I-80 Thursday afternoon. However, very few
impacts are expected as rain amounts will be quite light (generally
less than 0.10" even in the eastern sierra) with limited forcing
and snow levels near and above 10,000 feet. Increased cloud cover
and slight cooling aloft with the flattening ridge will limit
heating a bit, reducing the probability of reaching thursday's
record high of 69 degrees at Reno.
The ridge rebuilds again Friday, reducing rain chances although
widespread high cloud cover and more limited mixing will likely
result in temperatures near or even several degrees cooler than
Long term...Saturday through Tuesday...
some significant changes to the forecast for the storm expected to
move through at the end of the Holiday weekend. The changes were
to increase winds for Saturday, most along the 395 corridor. Also,
snow levels were significantly lowered for Sunday into Sunday
night by 1000+ feet. Be prepared for significant travel impacts at
the end of the Holiday weekend, with several hour delays possible
over the Sierra passes Sunday afternoon into Sunday night due to
Ec/GFS are more in line with the storm coming through in 2 waves.
The first warmer one is Saturday and Saturday night with the
second, colder one for Sunday afternoon into Sunday night. The
models are also consistent from 24 hours ago with snow levels
crashing behind a strong cold front Sunday night.
Winds will be gusty by Saturday afternoon into Sunday night with
ridge gusts over 100 mph at times from the Southwest. Valley gusts
are likely to be 45-55 mph, but stronger gusts over 60 mph are
possible along the 395 corridor. The winds will back off quite a
bit by Monday morning.
Precipitation will begin as rain Saturday afternoon for most areas
as snow levels are 8000+ feet. The rain will begin mainly north of
I-80 then slowly spread south and east into Sunday afternoon in
the mountains. Western Nevada will remain mostly dry through this
time except for the Tahoe basin and north of Gerlach. Snow levels
will also gradually fall about 1000-1500 feet and begin to affect
the passes sometime Sunday afternoon.
Sunday night the strong cold front will move through with snow
levels falling to the valley floors near and north of Highway 50
Monday morning. The good news is that most, if not all, of the
precip will have ended by that time. Still, several inches of snow
are likely for the passes, possibly even down to lake level in the
Tahoe basin and to 5000 feet in Lassen County. Mono County will
see some snow down to 7000 feet. At this time, no snow
accumulation is expected below 5000 feet in western Nevada.
Monday will be much colder behind the front, some 25 degrees
colder than today's highs. Of course, it will feel quite cold due
to the brisk west-northwest winds and the recent warm weather despite the
highs only being slightly below average.
Ridging rebuilds Tuesday with lighter winds and warming
temperatures for the mountains. Valleys will remain cold beneath a
moderate inversion as the likely clear skies result in good
VFR today except for some IFR for fog in the Tahoe basin through
18z along with portions of the Sierra Valley. VFR conditions
continue into Friday with some more mid and low cloud cover
Thursday as a weakening cold front moves through. Winds will be
light for the valleys, but ridges will gust to 50 kts at times
especially Thursday and Friday.
A potent Pacific storm is likely beginning Saturday into Sunday
with strong winds for 36+ hours. Ridge winds of 50+ kts, Strong
Mountain waves with turbulence and low level wind shear are likely. Rain and snow
will move in with the greatest impacts Sunday and Sunday night
with IFR conditions likely in the Sierra and brief periods of MVFR
ceilings in western Nevada overnight Sunday night.