Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 102307

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
407 PM MST Sun Dec 10 2017

.SHORT TERM...(Tonight through Monday night)
Issued at 100 PM MST Sun Dec 10 2017

Visible satellite imagery shows clear skies over all of eastern
Utah and western Colorado as the region sits on the eastern
periphery of a sprawling ridge of high pressure over the Great
Basin. This ridge will dominate both the short and long term
forecasts and provide dry and mainly clear skies through Friday.
Radiational cooling and valley inversions continue to be the
primary forecast challenges in the short term. As was the case
yesterday, have nudged bias-corrected MOS forecasts downward in
several of the higher elevation valleys. Persistence will be the
name of the game in forecasting both high and low temperatures
through Monday night.

.LONG TERM...(Tuesday through Sunday)
Issued at 100 PM MST Sun Dec 10 2017

Dry weather and light northwesterly flow aloft will remain in
place through the entire week as a strong Rex/Omega block pattern
aids in the persistence of the western ridge. The 12z ECMWF
brings a weak clipper system to the front range after midnight on
Thursday morning, however areas west of the divide should only see
a few high clouds drifting southward with this event. High temperatures
throughout the week will run 5 to 10 degrees above average. By
Saturday morning, medium- range guidance has consistently shown a
shortwave trough ejecting through the northern Rockies over the
past several runs. Unfortunately for now, any meaningful moisture
looks to stay north of the Wyoming border on Saturday with only a
few light snow showers in the highest elevations of the Park
Range. Ensemble guidance has backed off today with regard to the
breakdown of the western ridge in the day 7-9 timeframe. GEFS and
EPS mean 500mb heights remain around 1 sigma next weekend, despite
deterministic runs hinting at the jet stream dipping southward
and into our northern zones. Until more consistency is seen in
long-term runs, forecasts will favor the drier and warmer ensemble
guidance solutions.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 406 PM MST Sun Dec 10 2017

Clear skies with VFR conditions are expected at all terminals
through the period. Overnight winds will follow typical downvalley




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