Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 052122

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
222 PM MST Tue Dec 5 2017

.SHORT TERM...(Tonight through Wednesday night)
Issued at 200 PM MST Tue Dec 5 2017

Afternoon GOES satellite imagery reveals clear skies over eastern
Utah and western Colorado. A ridge of high pressure has moved in
along the Pacific coastline and will control the weather pattern
for the entire forecast period. The western slope will remain on
the eastern fringes of this ridge, resulting in northwest flow
aloft and temperatures running near seasonal averages in the short
term. Valley inversions will play a large role in forecasting
overnight several of the typical cold spots (GUC, CAG,
etc) will run at or below the coldest available guidance for
Tuesday and Wednesday night. On Wednesday, a few high clouds will
drift southward out of Wyoming, otherwise mostly sunny skies are
expected through the short term.

.LONG TERM...(Thursday through Tuesday)
Issued at 200 PM MST Tue Dec 5 2017

The only meaningful event in the entire 7-day forecast arrives on
Thursday. A weak vort max will dive southward out of Canada along
the eastern periphery of the large west coast ridge. Expect a
slight uptick in northerly winds in the high terrain on Thursday
afternoon as this system skirts our eastern zones. Analysis of
several model soundings along the Continental Divide does reveal
saturation in the 700-500mb layer, co-located with the dendritic
growth zone for around a 6-hour period. Confidence has increased
today that the highest elevations of the Park, Flat Top, Gore,
and northern Sawatch ranges will see around an inch or two of snow
from Thursday afternoon through midnight Friday.

After this system, the large-scale ridge along the west coast
strengthens and builds eastward. Dry weather and above average
temperatures are all but a guarantee from Friday through the
remainder of the forecast period. Looking beyond Week 1, GEFS and
EPS ensemble guidance remain locked-in on an extremely dry pattern
through mid- December. 500mb height anomalies remain 2 to 3 sigma
over the west through Day 10 and ensemble mean QPF forecasts have
0 precipitation west of the Divide during this stretch. There is
some indication that the western ridge may begin to break down for
the second half of the month (beyond week 2), however any skill
in forecasting specific precipitation events at that range is


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1043 AM MST Tue Dec 5 2017

Other than a couple of lingering clouds over Routt County, eastern
Utah and western Colorado will continue to be cloudless over the
next 12 hours. Some high clouds will likely move into the north
central Colorado valleys after 06z tonight with winds picking up
a few kts on the whole around this time as well.




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