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Area forecast discussion 
National Weather Service Grand Junction Colorado
246 PM MST Friday Nov 28 2014

Short term...(tonight through Saturday night)
issued at 245 PM MST Friday Nov 28 2014

A low amplitude upper ridge was over the Great Basin and southwest
today. A small disturbance was pushing high cloud across NE Utah/northwest
Colorado. These clouds will thin tonight for another clear/mostly clear
sky with low temperatures similar to last night. Fog was observed in the
Steamboat spgs area this morning. Will include patchy fog in the
forecast there tonight.

The upper level jet stretched from the Pacific northwest to the
northern plains and upper Midwest today. A middle-level shortwave
trough over southwest British Columbia will swing southeast across
the northern rockies on Saturday. This will cause the upper jet to also
sag southward. Mountain top winds will continue but shift more to the
southwest on Saturday. Small embedded disturbances will ripple
though the southern fringe of the jet for some cloudiness across
the north Saturday and Saturday night. Moisture remains mainly in
the middle and upper levels though...with the chance of precipitation
Saturday night slim in the far north to none central and south.
Associated surface cold front looks to sag into southern Wyoming by Sunday

Long term...(sunday through friday)
issued at 245 PM MST Friday Nov 28 2014

As a weak shortwave trough ejects into the northern plains on
sun...a trailing cold front will sag along the Colorado/Wyoming border.
Models indicate a narrow band of precipitation will develop along
the border beginning early sun and will continue Sun night. The
upper jet will be shifting off into the plains on Sunday...but
another jetlet will approach western Colorado during the evening
possibly providing a weak boost in upper difluence between the
right entrance and left exit regions of the two jets. Showers will
develop over the eastern uintas and along the Colorado/Wyoming border early
sun as the trough axis sweeps by the area. The focus then shifts
east to the higher northern Colorado mountains...with peak activity over
the Elk Head and northern park ranges sun evening. Northern
valleys from Craig eastward will see a chance of precipitation...
possibly rain or mixed phase initially and becoming all snow by
late evening. A few inches of snow will be possible over the above
mentioned mountains.

The next system of interest is a closed low off the California
coast that will approach the West Coast on Tuesday. This low will
weaken into an open trough as it moves onshore over central to
northern California Tuesday night. It also appears that this system
will not remain all that cohesive but will break into a couple of
waves as it tracks across the western Continental U.S. Through Wednesday and Wednesday
night. Models continue to show differences in the details. But
they do agree that a sub-tropical moisture fetch will spread into
the area from the southwest beginning Tuesday afternoon ahead of the
trough. The GFS remains faster and cooler than the European model (ecmwf)...but it
does look like the chance for precipitation will begin by Tuesday
evening. Probability of precipitation still remain on the low side through this event due
to model uncertainties...and the unorganized nature of the
disturbance. The chance for mountain snow will continue through
Wednesday night and possibly into Thursday morning. The southern mountains
will initially be favored...with activity shifting to other
mountains by early Wednesday. Due to the Pacific origin...temperatures
will remain fairly mild with relatively high snow
levels...especially through Tuesday evening.

Models show a relatively Flat Ridge developing behind this
disturbance and dominating through the end of the work week.


Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 245 PM MST Friday Nov 28 2014

Ridge of high pressure will bring stable conditions this afternoon
and evening. VFR conditions are expected at all taf sites through
00z Sunday with mainly just high clouds streaming across in west
then southwest flow. Mechanical and Lee-side turbulence possible
with the stronger winds at mountain top level.


Gjt watches/warnings/advisories...


Short term...jad

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