Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Reno Nevada
252 am PST Sat Dec 3 2016
ridging over the Sierra and western Nevada will result in light
winds and limited mixing today. Temperatures will warm on Sunday
with breezy conditions ahead of the next systems moving into the
area Monday and Tuesday. Warmer and wetter pattern sets up by the
end of the week.
shortwave ridging already building across the west this morning,
which will trap colder air in the valleys and result in limited
mixing today. Temperatures will be similar to yesterday with lower
valleys in the low to mid 40s and the 20s and 30s for the Sierra.
Ridge winds will remain gusty for areas south of Highway 50 in
the Sierra, especially across the higher terrain in Mono County.
Upper level flow will begin to decrease later tonight which will
allow the winds to drop off.
Surface inversions are expected to mix out on Sunday as southwest
flow increases across the Sierra and western Nevada. Mixing will
allow the afternoon high temperatures to warm significantly with
some locations in the mid 50s, well above normal for this time of
year. The timing of the front has continued to slow down with
this initial system for Sunday night into Monday. The best
moisture and dynamics with this system remain over central-
eastern Nevada, but we should still see some light snow showers
across the area on Monday. Best chances for precipitation and
light accumulations will be north of Interstate 80.
Monday will be breezy and cold, but we may see a short break in
shower activity during the day as drier air works in just behind
the front. The latest model runs show the upper low tracking south
into western Nevada around early Tuesday morning. -Edan
Long term...Tuesday through Friday...
the cold inside slider will continue to move through during the day
Tuesday with the ec continuing to be the furthest west. The GFS is a
little further west than yesterday, but it is still further east
than the ec ensemble. Trended the forecast a little more to the ec
and its ensemble and increased the threat of snow showers north
of Highway 50 some. Depending on timing, there could be issues
during rush hour Tuesday morning.
Despite the differences in precip, all models agree on very cold air
arriving behind the cold front. Temperatures will be in the upper
20s and 30s for highs both Tuesday and Wednesday. A very cold night
is possible Tuesday night with a few below zero readings in Sierra
valleys depending on snow cover.
Then, the next system will begin to arrive late Thursday into
Friday. It looks to have a weak to moderate Arkansas with it, although the
models are not showing the system overall to be organized. Clouds
will be the main influence into Thursday afternoon before rain and
snow arrive that evening and into Friday. With this storm not
being organized, how it plays out is low confidence, especially
with snow levels.
There is the potential for cold air damming as the precip shield
moves in which would keep the snow levels at the valley floors. Of
course, if the winds aloft mix down (and they aren't that strong so
it may not occur) the snow levels could start as high as 7000 feet.
For now, have put in a very thick mixed layer to account for the
very low confidence in precip type. I also backed off on the winds
this morning as they do not look that strong aloft (only to 40-45
kts), and the potential for cold air damming could keep them limited
to the ridges.
VFR conditions with lighter east winds today and tonight. Some west
winds gusting to 25 kts Sunday in the valleys and up to 50 kts on
the ridges with some mtn wave turbulence ahead of the next cold
front. At this time, do not expect significant low level wind shear. Some snow
showers are possible at the terminals Monday afternoon into Tuesday.
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