Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 160511

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1011 PM MST Wed Nov 15 2017

.SHORT TERM...(Tonight through Thursday night)
Issued at 359 PM MST Wed Nov 15 2017

W-SW flow aloft expected to turn a little more southwesterly and
increase in velocity Thursday ahead of approaching Pacific
trough. Still expecting breezy SW surface winds by afternoon in
many areas, especially in mountain zones, as stronger winds aloft
mix down to the surface.

Still have some smoke in the air across portions of western
Colorado from prescribed burns. The smoke won`t be noticeable
tonight, and then should begin thinning out by late Thursday
morning as winds start to pick up.

Still expect max temperatures Thursday to again be generally 15-20
F above normal, even though clouds will be increasing across our
CWA. Could even be a few rain showers over the eastern Uinta
Mountains by Thursday afternoon.

Then the greater push of moisture will be moving into our area
Thursday night with increasing chance of showers mainly mountains.
Snow levels will initially be quite high, above 9K feet north and
10K feet south.

.LONG TERM...(Friday through Wednesday)
Issued at 359 PM MST Wed Nov 15 2017

Surface cold front expected to start pushing slowly southward
across our CWA on Friday as upper trough starts moving closer
towards our area. Snow levels not expected to drop below 9000 foot
level in our southern zones until Friday evening. Then by
Saturday morning the moisture and dynamic lift should be east of
our area as the progressive trough screams eastward under the
influence of a 125 kt plus jet. So, this should be a relatively
short period of snowfall for our CWA.

Hoisted a Winter Storm Watch for late Thursday evening through
late Friday night for our higher western CO mountains. NW CO
mountains should have the best chance of widespread significant
snow accumulations, heavy in some areas. In our central CO
mountains, significant snowfall accumulations should be above 8000
feet. And in our SW CO mountains, significant snowfall
accumulations should be quite high in elevation, at least above
9500 foot level, with amounts barely reaching warning criteria.

Post trough, much colder air expected for our CWA on Saturday
under a NW flow aloft. However, this much colder air will
actually result in nothing more than near normal max temperatures
on Saturday.

By Sunday a migratory ridge axis over our area and WAA should
result in a recovery of max temperatures generally 10F higher
than Saturday.

On Monday, models diverge on outcomes. GFS indicating a shortwave
trough brushing our area on Monday with some showers, while EC
and Canadian dampen out the shortwave so much that no precip would
be expected from those models. Confidence in model outcomes for
Monday is rather minimal.

Then the models are back in general agreement for our area
thereafter, indicating a dry N-NW flow over our area for Tuesday
and Wednesday, though positioning of upper trough axis in the west
varies widely. This will influence max temperatures, with
potential variations between models of at least 5F.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1000 PM MST Wed Nov 15 2017

VFR conditions with CIGS above ILS breakpoints will continue at
all TAF sites in eastern Utah and western Colorado through the
next 24 hours. Winds will be terrain driven in the valleys
overnight then mountain winds will increase from the southwest
through the day on Thursday. Mid and high level clouds will
increase through the day, with snow showers beginning above
treeline in the northern and central mountains of CO and UT by


CO...Winter Storm Watch from Thursday evening through late Friday
     night for COZ004-009-010-012-013-018-019.



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