Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181103

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
503 AM MDT Thu May 18 2017

.SHORT TERM...(Today through Friday)
Issued at 430 AM MDT Thu May 18 2017

The closed low pressure system responsible for the return to more
wintry conditions was centered just south of the Great Salt Lake
early this morning. Moisture streaming northward across the
Colorado Rockies in the broad area of large-scale ascent fed
widespread precipitation, mostly falling in the form of snow.
Snotels, spotter reports and public reports from social media
indicated accumulations generally ranged from 4 to 6 inches with
some locally higher amounts.

A lobe of vorticity moving through the base of the trough was
just beginning to swing northeastward over the Four Corners area
and was forecast to move northward over the Colorado mountains
during the day. Models indicated that lift associated with this
feature will enhance mountain snowfall over the central and
northern Colorado mountains. Meanwhile, rising temperatures will
cause snow to transition to either a rain-snow mix or all rain in
the central valleys during the latter part of the morning and
early afternoon. Therefore, am comfortable with noon expiration
time for the Winter Weather Advisories in place for the central
and northwest Colorado valleys. In contrast, snow will continue to
pile up in the mountains as temperatures remain cold enough for
snow down to near 8000 feet with a mix of rain and snow at their
bases. The eastern Uinta mountains, which have seen a bit of lull
overnight, will see snow increase today as the low center wobbles
over central Colorado bringing a more favorable northeast flow.
Afternoon highs will be the cooler than yesterday and some of the
coolest experienced in some time.

Models suggest snowfall intensity will decrease as the low pushes
east of the Continental Divide late tonight, but coverage should
continue to be widespread. Another round of unseasonably cold
overnight lows in store for the region with some lower valleys
facing a potential freeze. Therefore, hoisted another Freeze Watch
for portions of southwest Colorado.

Drier air begins to fill in over eastern Utah and the westernmost
counties of Colorado on Friday. However, residual moisture and
instability is expected to continue to generate snow showers over
Colorado`s central mountains. However, additional accumulations
should be more localized as coverage becomes more scattered.
Partial sunshine and weak warm air advection will bring some
warming to the area. However, expect afternoon highs will peak
well short of seasonal norms.

.LONG TERM...(Friday night through Wednesday)
Issued at 430 AM MDT Thu May 18 2017

A ridge of high pressure building over the western states will
help push this trough eastward with a drier northwest flow taking
hold by Saturday morning. Some convection may develop over the
higher terrain on Saturday afternoon but coverage looks isolated
at best. This upper low will move northeast and park itself over
Ontario and the northern Great Lakes, with shortwave disturbances
rotating around the upper low and clipping our area in a
persistent northwest flow. This will result in afternoon and
evening convective showers developing each day from Sunday through
Wednesday as a series of disturbances move through each day. Kept
chance precip each afternoon over the higher terrain with an
overall improving trend in terms of temperatures, rising towards
more normal values for this time of year.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 503 AM MDT Thu May 18 2017

Widespread rain and snow will keep CIGS below ILS breakpoints with
MVFR VSBY in snow at all but the eastern Utah TAF sites this
morning. Conditions improve somewhat during the afternoon, though
the potential for additional showers will be high through this
evening. Fog potential is good later tonight.



CO...Freeze Warning until 10 AM MDT this morning for COZ020-021.

     Winter Weather Advisory until 6 PM MDT Friday for COZ003-004-009-

     Freeze Watch from late tonight through Friday morning for COZ011-

     Winter Weather Advisory until noon MDT today for COZ002-005-008-

UT...Freeze Warning until 10 AM MDT this morning for UTZ024.

     Winter Weather Advisory until 6 PM MDT Friday for UTZ023.



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