Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 062040

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
140 PM MST Wed Dec 6 2017

.SHORT TERM...(Tonight through Thursday night)
Issued at 140 PM MST Wed Dec 6 2017

Water vapor imagery is currently showing some drier air
undercutting the weak shortwave that is moving southward through
Wyoming and northern Colorado. This dry air is entrenched across
much of central and southern Utah into southwest Colorado. Do not
expect too much in the way of snow accumulation over the mountains
with this weak shortwave today with a few flurries due to the dry
atmosphere. Another wave comes in on the heels of this one on
Thursday, clipping the northern divide mountains again for maybe a
couple inches of light snow at best among the higher peaks.
Clouds will increase across the northern and central divide
mountains but otherwise, expect mostly sunny skies for most areas
due to the lack of moisture. While snow and moisture may not be
much of a player through Thursday with these weak shortwaves, one
thing that will be a player is the cold air mass that moves in
this evening. H7 temps lower to between -10C and -16C across the
entire forecast area down to the Four Corners tonight through
Thursday afternoon. Therefore, lowered afternoon highs and
overnight lows today through Thursday night and trended more
towards the non-bias corrected guidance as it looked more
reasonable. Expect near normal temps this afternoon lowering to
below normal through Thursday night.

.LONG TERM...(Friday through Wednesday)
Issued at 140 PM MST Wed Dec 6 2017

What more is there to say other than that strongly amplified ridge
of high pressure along the western states, stretching from the
Baja to as far north as the Aleutian Islands in southern Alaska
will hold strong through at least mid December, which is as far
as the model forecasts go. This will result in dry conditions
with not much chance of precipitation as any disturbances hitting
this ridge will take a while to ride up and over the top of the
ridge and weaken as they reach Colorado, resulting in some high
clouds from time to time. Bottom line: the stubborn ridge of high
pressure is not budging. The biggest forecast challenge is the
temperatures, as valley inversions strengthen under this ridge,
slowing the warming trend through the weekend and into next week.
The nighttime lows especially will feel colder compared to where
we have been with highs gradually reaching near normal by Sunday
and above normal next week. Lowered temps through the weekend in
order to show a more gradual warming trend heading into next


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 957 AM MST Wed Dec 6 2017

A passing disturbance in northerly flow aloft will result in some
light snow showers along the Continental Divide in northern and
central Colorado tonight and Thursday morning. The disturbance
will also bring north or northwest winds during the afternoon.
Showers won`t impact TAF sites so expect VFR conditions and CIGS
above ILS breakpoints through the next 24 hours.




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