Area Forecast Discussion
Issued by NWS Grand Junction, CO

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137
FXUS65 KGJT 302218
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
318 PM MST Wed Nov 30 2016

.SHORT TERM...(Tonight through Thursday night)
Issued at 315 PM MST Wed Nov 30 2016

Despite weak ridging aloft this Wednesday afternoon, a shallow,
saturated dendritic growth layer combined with light upslope flow
has kept some snow showers going in the northern mountains of
western Colorado. The 500mb ridge axis is currently progged to
cross the UT/CO border before midnight tonight. As it does,
additional moisture around 700mb will advect eastward into the
region with cloud cover increasing throughout eastern Utah and
western Colorado overnight. PoPs steadily increase north of I-70
through the morning hours on Thursday before peaking later in the
afternoon across. 12z guidance is in good agreement portraying a
relatively meager snowfall event across the region in comparison to
the most recent systems. The most snowfall with the Thursday event
will fall over the eastern Uintas and Flat Tops...where 3 to 6
inches are likely through the evening. Lesser amounts, in the 1 to 3
inch range, are likely in the Book Cliffs and Grand Mesa area
before daybreak Friday.

.LONG TERM...(Friday through Wednesday)
Issued at 315 PM MST Wed Nov 30 2016

The shortwave trough responsible for light snow on Thursday will
dive south through Utah and close off south of the Four Corners
later on Friday afternoon. As it does, upper-level support for
light snow will diminish north of I-70 and precipitation will
taper off in all but the highest terrain after noon. Subtle
dynamic support for snowfall in the form of upper-level
divergence, as well as easterly flow below 700mb, will increase in
the southern Rockies on Friday afternoon. At the moment, guidance
is generally in agreement on a secondary maximum of light to
moderate snowfall developing over the central and southern
Colorado mountains including the Elk, Sawatch, and San Juan ranges
from noon Friday through early morning Saturday. A general 3 to 6
inch snowfall is likely across these regions by the time
precipitation ends by sunrise Saturday morning.

Dry northwest flow will return to the region on Saturday morning.
The break in the action will be short lived however, as low-level
moisture and upslope flow combine to return some light snow to the
northern Park range from Saturday afternoon through early Sunday
morning. At the moment, the NAM remains a bit of an outlier
showing enough moisture to produce some light snow in the north,
with the GFS and ECMWF depicting a drier solution for now.

After several weak systems late this week and weekend, a dramatic
change is in store for early next week as a more potent trough
dives through the Pacifc Northwest on Monday. Medium-range
guidance is in good agreement on the first piece of energy with
this system bringing precipitation to eastern Utah and western
Colorado beginning early Monday morning and lasting through
daybreak Tuesday. Thereafter, notable differences between
deterministic models emerge. The GFS develops an area of low
pressure over eastern Utah producing significant precipitation
over much of the central Rockies. The ECMWF develops this low
farther south, keeping the heaviest precipitation south of the
Interstate 70 corridor. Regardless of the outcome, cold air will
be plentiful from Tuesday onward with GEFS ensembles showing
500mb height anomalies 2 to 3 standard deviations below mean
values. Rocky Mountain snow lovers will certainly want to keep an
eye on the forecast over the next several days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1036 AM MST Wed Nov 30 2016

VFR conditions will continue at TAF sites across the area through
the next 24 hours. However, scattered snow showers will continue
off and on over the northern mountains throughout the period.
Expect light winds.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...NL



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