Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 191655
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
955 AM MST Sat Jan 19 2019

.SHORT TERM...(Today through Sunday)
Issued at 235 AM MST Sat Jan 19 2019

Patchy low clouds, fog and a few light snow showers will linger
over the higher valleys and near the divide this morning as we
continue to erode away the remnants of this most recent storm. The
big story today will be rising heights across the Great Basin as
ridging builds in from the west. This will bring drier conditions
through this weekend with light winds and temperatures climbing
into that normal range. The exception will be the snow covered
valleys where stronger inversions are expected to develop and help
knock temps back a bit. Have undercut a few of our colder valleys
over the next few nights, especially for the overnight periods.
Otherwise, MOS numbers appear reasonable.

.LONG TERM...(Sunday night through Friday)
Issued at 235 AM MST Sat Jan 19 2019

All eyes turn to our next winter storm system set to move through
the central Rockies on Monday and Tuesday. Forecast guidance has
continued to slow slightly with respect to the onset of snow on
Monday. It now appears as though any accumulating snow will hold
off until around the noontime hour, beginning first in the
northern mountains and spreading south and eastward throughout the
afternoon. Another notable trend is slightly less precipitation,
consistent across the GFS, ECMWF, and NAM. Previous model cycles
indicated enough liquid QPF in from this event to support a broad
range of 6- 12 inches of snow across all mountain ranges. As of
the 00z cycle tonight, we now sit on the lower end of that snow
total range. The San Juans remain on the southern extent of the
precipitation shield, and will likely end up with less than
mountain ranges to the north. Valley precipitation totals have
taken a downturn as well on the 0z model cycle. While plenty of
cold air will be in place to support snow all the way to valley
floors (700mb temps falling from -8C to - 12C), only a few
hundredths of an inch of QPF are forecast at places such as Grand
Junction, Montrose, Moab and Durango. Snow totals will very likely
be an inch or less in these locations. So why the drop in
precipitation totals tonight? It appears as though the Pacific
moisture connection associated with the Monday storm is pushed
slightly farther north as it comes ashore, possibly due to a bit
more ridging over the southwestern CONUS preceding this event. In
prior runs, the moisture feed was more east-west, coming in over
the Sierra and roughly following the I-80 corridor. With a bit
more longitudinal tilt, more moisture is used up by the California
ranges, leaving the central Rockies with less to work with. We
will see if things flop back tomorrow, or if this trend is here to
stay.

After a break in the action on Tuesday night and Wednesday morning,
fast flow carrying Pacific moisture moves back in over northern Utah
and Colorado on Wednesday evening into Thursday morning. Differences
in global models emerge by this time, with the GFS keeping things
farther west with a better opportunity for snow, and the ECMWF
sliding things eastward resulting in a drier forecast. Pure
northwest flow systems have not been common this season so far, so
will play a conservative route with precipitation amounts for now.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 949 AM MST Sat Jan 19 2019

VFR conditions will prevail for the next 24 hours under nearly
clear skies. KHDN is the only exception and should see scattered
low clouds with bases below 500 feet today and tonight but at this
time do not believe an IFR CIG will develop after dark tonight
and conditions will remain VFR.

&&

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

$$

SHORT TERM...JDC
LONG TERM...MAC
AVIATION...CC


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