Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 120450

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
950 PM MST Mon Dec 11 2017

.SHORT TERM...(Tonight through Tuesday night)
Issued at 1220 PM MST Mon Dec 11 2017

Clear skies continue over eastern Utah and western Colorado this
Monday afternoon. The large ridge centered over the Great Basin
will dominate the forecast through the short term with overnight
low temperatures remaining the only real forecast challenge. Have
lowered valley lows from guidance blends once again tonight and
Tuesday night. Afternoon highs will run 5 to 10 degrees average
both afternoons. As has been the case over the past several days,
valley inversions will result in poor smoke dispersal conditions
for anyone looking to burn through the early and middle portions
of the week.

.LONG TERM...(Wednesday through Monday)
Issued at 1220 PM MST Mon Dec 11 2017

A weak vorticity maximum will skirt southward along the eastern
fringes of the Great Basin ridge on Wednesday afternoon and
evening. This system will bring some increased cloud coverage to
both eastern Utah and western Colorado during that timeframe. GFS
and NAM soundings appear quite devoid of moisture below 600mb
during this time period, even along the Continental Divide. Have
kept a mention of a very slight chance of a snow shower along the
crest of the Park Range around midnight Thursday, however only the
EMCWF shows moisture near the surface at that time. Confidence is
high that this will be a non- event west of the Park Range.

Mainly sunny and dry weather resumes on Thursday and will last
until Saturday throughout all of Utah and Colorado. Medium-range
guidance has consistently indicated a shortwave trough passage on
Saturday/Sunday over the past few days of model cycles, matching
the ensemble h5 height trend at this time over the past week as
well. While this trough will be short-lived, it does present the
opportunity for some accumulating snow in the higher terrain along
and north of Interstate 70. Today`s 12z cycle is on the drier side
with both the GFS and ECMWF in the 2-5 inch range for the Parks
and an inch or two in the Gore and Flat Tops. Have kept PoP
chances rather conservative in today`s forecast package due to
consistency issues in recent QPF forecasts. Dry weather resumes
for Sunday evening and Monday.

For those looking for a shake-up in the overall dry weather
pattern, trends in ensemble guidance must be observed. Over the
past two days, GEFS/EPS 500mb height anomalies do show a downward
trend over the central Rockies during the Dec 21-25 timeframe.
Unfortunately, to the west of this feature another impressive
ridge develops just off the Pacific Coast. A pattern such as this
may be more conducive to quick clipper-like systems that bring
brief, light snow events to the higher terrain. However, any major
systems with strong Pacific moisture connections appear unlikely
for now.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 949 PM MST Mon Dec 11 2017

VFR conditions will prevail over the next 24 hours under nearly
clear skies and light diurnal winds.




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