Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 262228

Area Forecast Discussion
National Weather Service Grand Junction CO
328 PM MST Sat Nov 26 2016

.SHORT TERM...(Tonight through Sunday night)
Issued at 327 PM MST Sat Nov 26 2016

Clouds will begin to increase from southwest to northeast throughout
the evening as a 130+ kt jet nudges into the Four Corners. Short
term models indicate precipitation will begin over the San Juans
right around midnight tonight with precip becoming widespread by
daybreak as far north as the Tavaputs Plateau and Flattop
Mountains. The heaviest snowfall rates in the San Juans are
expected between midnight tonight and noon Sunday with 2-3"/hr
rates possible. Combined with these snow rates are going to be
some strong winds to 50 or 60 mph above 9000 feet. It won`t be a
good morning to be traveling in the backcountry or driving over
Molas, Coal Bank, and Red Mountain passes with visibilities near
zero with driving snow. The worst time period to travel in the San
Juans will be between about 2am and 8am. Winds will lessen a bit
after 8am as the upper level jet support moves eastward.

Even being 12-24 hours from the start of this storm, the
rain/snow line forecast continues to be a struggle so had to use
a moderate confidence factor in advisory issuances today. In the
SW Colorado valleys including Cortez east to Pagosa Springs, feel
confident that locations above 6000 ft will accumulate 1 to 4
inches overnight into the morning hours, though both Cortez and
Durango city centers will likely see rain to start and potentially
a late switchover to snow (Sun morn). Sounding at DRO at 09z
overnight indicates complete saturation 2000 ft above the sfc,
with below fzg dewpoints all of the way to the sfc. With strong H5
vorticity in place, think that heavy wet snow is definitely
possible, and areas along Highway 160 and the route to Mesa Verde
may be a big mess as well. The eastern Paradox valley including
Norwood and Nucla will likely see a bit of snow as well. As Sunday
morning progresses, east of New Castle along I-70 is likely to
deteriorate with westerly flow developing and models continuing
precip along the I-70 corridor throughout the next couple of days.
Same with the Craig/Meeker corridor, with a prolonged accumulating snow

A few spots still of concern where my confidence was just not
there for an issuance today - parts of the North Fork Valley
(zone 11) above 5500 ft may see a few inches of snow, namely
Paonia and the mesas around Hotchkiss. The De Beque to New Castle
corridor is another one to watch, and definitely want to watch
Steamboat as this storm transitions from SW flow to W/NW flow
Sunday night. MAV guidance indicating quite a bit of snow at
Steamboat, but this is later in forecast period and thinking the
GFS is overdoing amounts in snow since it is an outlier.

The initial trough and main vort max pushes clear through western
CO by mid afternoon Sunday, then orographic snow in
westerly/northwesterly flow continues throughout the day. By
Sunday night, the northern piece of the trough splits off and
closes off over the Dakotas.

.LONG TERM...(Monday through Saturday)
Issued at 327 PM MST Sat Nov 26 2016

The next well-defined part of this snowstorm will occur overnight
Monday through Tuesday morning as a secondary trough moves into
the region from the NW. The Rabbit Ears to Vail Pass to Aspen corridor
will likely continue to snow during much of the time between these
systems, but snow intensity will pick up again Monday evening.
Elsewhere snow should be over by early Tuesday. Conditions look to
finally improve on Wednesday morning along the Rabbit Ears to
Aspen corridor. Below normal temperatures will persist in the wake
of the storm systems.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1054 AM MST Sat Nov 26 2016

Sunny skies with VFR conditions will prevail through much of the
day today. High clouds will begin to invade from the south this
evening with rain and snow showers increasing after 06z Sunday.
Winds will also increase from the southwest as well at the
mountain TAF sites with gusts to 40 kt at KTEX and higher among
the ridges. Ceilings and visibilities will lower due to increasing
rain and snow with precipitation becoming widespread at all TAF
sites by 12z Sunday and beyond. Winds will cause areas of blowing
snow for mountain TAF sites and any southern valleys that switch
over to snow Sunday morning, including KDRO. Mountains will be
frequently obscured Sunday morning and beyond due to heavy snow
and blowing snow.


CO...Winter Weather Advisory from midnight tonight to 6 AM MST Monday
     for COZ017.

     Winter Storm Warning from midnight tonight to 6 AM MST Monday
     for COZ012-018-019.

     Winter Weather Advisory from 6 AM Sunday to 6 AM MST Monday for

     Winter Weather Advisory from midnight tonight to noon MST Sunday
     for COZ020>023.

     Winter Storm Warning from 6 AM Sunday to 6 AM MST Tuesday for

UT...Winter Weather Advisory from midnight tonight to 6 AM MST Monday
     for UTZ023.

     Winter Storm Warning from midnight tonight to 6 AM MST Monday
     for UTZ028.



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