Scientific Forecaster Discussion
fxus65 kslc 221046
Area forecast discussion
National Weather Service Salt Lake City Utah
346 am MST Tue Jan 22 2019
weak weather disturbances embedded in a moist northwest flow will
impact mainly northern Utah and southwest Wyoming during the
latter portion of the week.
Short term (through 00z saturday)...
clouds continue to scatter across the state as yesterday's winter
storm depart. Upslope stratus and a few light snow showers linger
across the central/southern mountains and on the north slopes of
the unitas this morning. Mid-level ridging continues to build in
from the west bringing increasingly dry air and subsidence. Thus
cloud cover and lingering snow showers will continue to diminish
today, with any additional mountain snow showers resulting in
Temperatures today will struggle to recover with the surface high
building over the area resulting in diminishing winds and
decreased mixing as an inversion develops by tonight. The fresh
snowpack will further help minimize diurnal heating and mixing.
Thus high temperatures will run about 10 degrees below normal
today, with most areas remaining below freezing, except for
Tonight the surface high settles across the area resulting in
light winds and generally good radiational cooling conditions over
fresh cover. Temperatures will readily drop, however, cloud cover
will increase over northern Utah later tonight ahead of our next
approaching storm system, which will help keep overnight lows from
completely tanking there. Still it will be a cold night, with
widespread readings in the teens and single digits, with a few
typical cold spots dipping below zero.
Warm advection and moisture advection peak Wednesday into
Wednesday night as the ridge is suppressed by a shortwave diving
from Washington state to southwest Wyoming. Moisture and forcing
are generally limited, with most of the resultant snow showers
tied to the mountainous terrain of northern Utah. Expect a few
inches of mountain snowfall, while lower elevation locations like
the Cache Valley could pick up an inch. The Wasatch front should
generally only see some virga or passing light snow showers with
dry low- level air in place and weak forcing.
The increased flow will help stir the valleys, along with increase
cloud cover will help prevent a Stout inversion from setting up
and will also help the valleys see some day-to-day temperature
moderation. Temperatures should return to normal values by
Thursday, along with diminishing mountain snow showers by Thursday
Long term (after 00z saturday)...
model trends have shifted a bit...bringing another shortwave
through Utah Friday. This wave is embedded in the continued
northwesterly flow resulting from a strong longwave trough across
the eastern US and an amplifying ridge off the Pacific coast.
Added low end pops into the forecast as this wave is Continental
in nature and is lacking significant moisture.
Upper level ridging builds eastward again through the remainder of
the weekend before another Continental wave digs southward across
the interior west early next week. The 00z operational GFS has
trended more toward the remainder of the global model guidance in
bringing this wave across Utah. Again, moisture will be
limited...but this should bring a round of showers to the region and
a reinforcement of the very cold temperatures. Current forecast
shows temperatures struggling to reach the freezing mark across much
of the area...and it could be considerably colder than that based on
some of the global solutions.
northwesterly winds will continue at the slc terminal through the
day. Otherwise...expect high pressure to continue to build into
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