Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Grand Junction Colorado
442 am MST Tue Dec 6 2016
Short term...(today through wednesday)
issued at 400 am MST Tue Dec 6 2016
Latest analyses indicated that the cold front associated with the
system which swept across the region yesterday had stalled near
the southern border of Utah and Colorado. Meanwhile, the short
wave trough responsible for driving the front southward across the
forecast area had moved to the Central Plains early this morning.
As a result, dynamic forcing was limited though orographic lift
working on marginal residual moisture continued to bring areas of
light snow to the central Colorado mountains during the night.
Models suggest localized light snow will continue over the central
mountains this morning. However, snow is expected to spread into
all but the southeast Utah mountains this afternoon ahead of the
next trough approaching from the northwest. Lift associated with
this system will peak tonight as the shortwave passes over the
forecast area. Snow will be widespread over the northern and
central Colorado mountains and heavy in some areas during the
night. Coverage and intensity will be less across the San Juans.
Meanwhile, winds will continue to generate areas of blowing snow
in the high country, shifting from west in the evening to
northwest with trough passage later tonight. Additional snow
accumulations are expected to range from 4 to 8 inches in the
northern and central mountains, and from 2 to 5 inches in the san
Juan's. Consequently, despite the current lull in activity, will
continue advisories for snow and blowing snow across the northern
and central mountains through 13z/Wed.
Snow decreases Wednesday as the trough shifts to the east and
drying works across the region from the west and northwest.
As expected temperatures will be cooler across the region today
and tonight behind the cold front described previously. However,
Wednesday will be the coldest day of the week as the second trough
system delivers another shot of cold air to the region. Single
digits and teens are expected across the mountains and northwest
Colorado, with 20s and lower 30s elsewhere.
Long term...(wednesday night through monday)
issued at 400 am MST Tue Dec 6 2016
Clearing and continued cold air advection will likely yield the
coldest temperatures so far this season. Forecast lows are
expected to be below zero in the mountains and north with single
digits and low teens elsewhere.
Temperatures begin to moderate Thursday as a shallow ridge forms
to the west. However, moisture working through the ridge is
expected to generate light snowfall over the eastern Uinta
Mountains and Colorado's northern and central mountains. In fact,
periods of snow are expected to persist off and on through the
extended period, mainly impacting the northern and central
mountains. Ferreting out the details difficult this weekend and
early next week as individual waves in zonal flow appear shallow
and poorly resolved. Differences in European model (ecmwf) and GFS attest to this.
What is more certain is that temperatures will continue to
recover, rising to near normal by Friday then changing little
Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 442 am MST Tue Dec 6 2016
Ceilings will hover near ils break points for kase and kege
early this morning, but not at remaining taf sites. As the next
system drops down from the northwest expect conditions to
deteriorate in the afternoon hours with snow possible after
00z/Wed or kase and kege. At these sites expect MVFR ceilings and
visibility in light snow with brief periods of IFR conditions possible.
VFR conditions are likely to continue at remaining taf sites.
Colorado...Winter Weather Advisory from 3 PM this afternoon to 6 am MST
Wednesday for coz008-009-012.
Winter Weather Advisory until 6 am MST Wednesday for coz004-010-
Short term...no layers
long term...no layers