Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 161808
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1208 PM MDT Sat Sep 16 2017

.SHORT TERM...(Today through Sunday)
Issued at 410 AM MDT Sat Sep 16 2017

Early this morning, scattered showers continued to sweep across
portions of western Colorado ahead of the low pressure trough
which drove a cold front across the region on Friday. The north-
south oriented trough axis had shifted just east of Salt Lake City
as of 09Z according to the latest RAP40 analysis. Models indicated
the trough axis will move over eastern Utah by sunrise, then
across western Colorado during the remainder of the morning.
Consequently, expect showers to persist over the northern and
central Colorado mountains with some shower activity moving over
adjacent valleys. As the trough axis swings east of the
Continental Divide showers will dissipate in the subsident
environment in the wake of the trough this afternoon. Today`s
highs will be cooler than normal again today as the airmass which
arrived in the wake of yesterday`s cold front lingers over the
region. Expect height packing in the base of the trough to
generate breezy westerly winds, especially across the north,
during the afternoon. Winds will diminish in the evening as the
gradient relaxes and the atmosphere decouples. Clearing skies and
light winds will lead to chilly temperatures early Sunday morning.

The models show some divergence of solutions as early as Sunday.
All agree that a shortwave trough will move over the forecast area
late Sunday afternoon and evening, but they disagree on how much
sensible weather will be generated over the area. The NAM12 has
consistently kept a dry slot over the area Sunday for the last
half dozen model runs. The GFS and EC show an embedded jet maxima
within the SW flow ahead of the main shortwave and this helps
generate isolated to scattered showers and thunderstorms over the
mountains near the Continental Divide and further west, over the
Flattops, the San Juans and the Uintas. Have somewhat split the
difference but leaned closer to the wetter models solutions as the
NAM12 is somewhat an outlier. Meanwhile, warm air advection in
southwesterly flow will bring warmer temperatures, especially
across the north on Sunday afternoon.

.LONG TERM...(Sunday night through Friday)
Issued at 410 AM MDT Sat Sep 16 2017

Regardless of the precipitation chances on Sunday and thereafter
the region will be have its first dose of Autumn-like weather this
weekend and next week. Cooler and drier conditions will dominate
from Monday through Wednesday and the jet stream will settle in
overhead which should produce consistent autumn breeziness each
day.

The next trough appears to be a big one. It pushes into the
Pacific Northwest Wednesday night and Thursday and begins to split
at it moves over the Great Basin Friday. A strong southwesterly
jet should produce a windy day Thursday while the cold front will
add some showers to those winds Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1208 PM MDT Sat Sep 16 2017

VFR conditions are in place behind the passing of the recent storm
system. LIFR conditions temporarily set up over the Eastern Uinta
valley due to the recent rainfall. Confidence not high this will
occur again overnight as the boundary layer dries out some in
today`s clear skies and higher clouds move in aloft tonight.
Something to keep an eye on. No other problems to aviation at the
forecast terminals expected over the next 24 hours.

&&

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

$$

SHORT TERM...NL/CC
LONG TERM...CC
AVIATION...TGJT



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