Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 200405

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
905 PM MST Fri Jan 19 2018

Issued at 905 PM MST Fri Jan 19 2018

Little change in the new runs this evening and have went ahead and
upgraded the winter storm watches to winter weather advisories for
the northern and central mountains in western Colorado, Have also
adjusted snow amounts down slightly with adjustments to our snow
ratio grids and temps. Lower valleys will likely see rain through
the afternoon hours, before flipping over to snow early Saturday
evening. Forecast soundings across the southern valleys suggest
temps will be above freezing into the evening hours with the
change over to snow delayed until between 7 and 9 pm.


.SHORT TERM...(Tonight through Saturday night)
Issued at 333 PM MST Fri Jan 19 2018

Southwest flow bringing strong WAA into the region will keep
temperatures mild this evening, and pump a swath of above normal
moisture for this time of year in from Baja CA. A -30C H5 open
wave is expected to push westward into Utah Saturday afternoon,
with showers developing along and ahead of the associated cold
front west to east during the day Saturday across eastern Utah and
western Colorado. Before the front even makes its way past NE
Utah, forecast models continue to indicate the front getting hung
up on the Uinta Mountains early Saturday, shown very vividly on
MSLP height plots. Because of the front stalling, snow amounts in
excess of a foot are likely across highway 191 and UT state route
44 from Manilla to Flaming Gorge and through the Uinta mountains.
Anticipating a sharp gradient in snow amounts between the eastern
Uinta mountains and the eastern Uinta basin in Vernal with
shadowing on the leeward side, but a couple of inches of snow will
be possible in the eastern Uinta basin. Weaker energy should
eject at mid and upper levels eastward late Saturday afternoon and
push the front into western Colorado. As the front pushes eastward
Saturday night, much of western Colorado will see rain and/or
snow with cooler air lowering snow levels throughout the night.

Areas normally favored in northwesterly flow (Routt Co south to
Pitkin Co and northern Gunnison Co) will not likely see any snow
until the mid level front reaches them Saturday night.

.LONG TERM...(Sunday through Friday)
Issued at 333 PM MST Fri Jan 19 2018

Closed Colorado low will strengthen on the Front Range Sunday
morning, with upper level support following. Wrap around moisture
with primo dendritic crystal growth on Sunday morning may bring
good snowfall rates across the central CO mountains for the first
part of the day before orographic snowfall ends later in the day
with the ejection of the closed low eastward across Kansas.

A stable and cool airmass will develop on Monday behind the front,
but forecast models are trending toward zonal flow and possibly a
weak disturbance Monday into Tuesday bringing light snow to the
northcentral Colorado mountains.

Southwest flow increases on Thursday ahead of the next weather
maker rolling in from the west on Friday. Additional snow will be
possibly late next week into the early weekend.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 905 PM MST Fri Jan 19 2018

Mid and high level cloudiness will continue to stream overhead on
strong southwesterly flow ahead of the next system. Mountain
wave turbulence could be an issue overhead while down at the
surface lighter winds are expected. CIGS will lower Saturday
morning but the only impact at this time will be at KVEL where the
snow will developing after sunrise and MVFR conditions are
expected to develop. TAF sites in western Colorado will be
impacted during the afternoon into the evening hours as a strong
cold front pushes east across the region. Expect frequent mountain
obscuration to develop after 22Z Saturday afternoon.


CO...Winter Weather Advisory from 2 PM Saturday to 2 PM MST Sunday
     for COZ003-009-012-017>019.

     Winter Weather Advisory from 6 PM Saturday to 9 PM MST Sunday
     for COZ004-010-013.

     Winter Weather Advisory from 6 PM Saturday to 10 AM MST Sunday
     for COZ001.

UT...Winter Weather Advisory from 10 AM Saturday to 10 AM MST Sunday
     for UTZ025-028.

     Winter Storm Warning from midnight tonight to 6 AM MST Sunday
     for UTZ023.



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