Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 211705

Area Forecast Discussion
National Weather Service Grand Junction CO
1005 AM MST Sat Jan 21 2017

Issued at 1005 AM MST Sat Jan 21 2017

Shortwave working across northern New Mexico providing excellent
southerly push across the southern valleys this morning. Webcams
and spotters reports indicating heavy snow falling in the region
with reports of up to 16 inches near Yellow Jacket and 8+ inches
in the vicinity of Durango. HiRes models shutting things down by
mid-afternoon, but NAM and GFS slower keeping things around until
this evening. With winds starting to swing around to the west and
the main vort center pulling away, things will start tapering off
this afternoon with showers ending this evening. Also dropped max
temps several degrees across the southern valleys with snow and
cloud cover keeping things in check. Reworked qpf and snow amounts
for expected conditions through this evening resulting in slight
adjustments to snowfall amounts.

UPDATE Issued at 728 AM MST Sat Jan 21 2017

Snow showers increasing in coverage across western Colorado this
morning with light to moderate snow spreading into the west
central valleys. Expect slushy conds to develop on roadways under
the heavier snow showers with likely impacts to travel this
morning. As a result, issued a winter weather advisory through
early this afternoon for the Montrose, Grand Junction and Rifle
areas, including Highway 50 and Interstate 70. Expecting to see a
quick 1 to 3 inches with up to 4 along the higher terrain between
DeBeque and Rifle.


.SHORT TERM...(Today through Sunday)
Issued at 233 AM MST Sat Jan 21 2017

As predicted by previous forecasters, snow increased in coverage
and intensity over southeast Utah and southwest Colorado early
this morning. Models indicated broad ascent responsible for snow
was provided by combined jet divergence, a passing 7H trough,
steep lapse rates and favorable south to southwest orographic
lift. Models further suggest that these favorable conditions will
perish through sunrise assuring additional snowfall across the
Four Corners region along with the San Juan, Abajo and La Sal
mountains. Meanwhile, the central and northern mountains remained
in a bit of a lull overnight.

Expect this will change during the afternoon when flow shifts to
the northwest and lapse rates steepen further in response to
cooling aloft. Instability, lingering moisture and orographic lift
will keep snow going in the mountains tonight. Consequently, given
all that was discussed previously will continue current
highlights, though will cancel the WW.Y for CO zone 8 where snow
hasn`t fallen since yesterday afternoon.

The third in a series of storms to move through the the area
stretching back to Thursday will begin to impact the area as early
as Sunday afternoon. Eastern Utah and the San Juan mountains
appeared favored during the early phase of the storm and PoP
fields have been adjusted to reflect this potential.

.LONG TERM...(Sunday night through Friday)
Issued at 233 AM MST Sat Jan 21 2017

The extended forecast will begin with the last storm in this trio
beginning to move through as early as Sunday evening in the west.
There will be a decent break on Sunday as a more substantial ridge
moves over the Rockies. Ensembles indicate another strong tap to
the deep Pacific moisture source and anomalously high PWAT is once
again directed across the 4 Corners as the main system moves into
Great Basin. Strong ascent from the upper jet and approaching
system will combine with the moisture and increasing instability
will likely produce decent snow banding in the Monday into Tuesday
portion of this storm. Cold advection and strong orographics take
over Tuesday night into Wednesday night as the back side of this
storm slowly works through. This will likely be another really
good storm for the area. During the latter part of the week
amplified ridging will dominate the West Coast with a deep trough
blocking downstream over the eastern states.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1000 AM MST Sat Jan 21 2017

Winter weather will continue to bring significant impacts TAF
sites as a winter storm continues to move through. KDRO, KGJT,
KCNY and KVEL will have IFR/LIFR and periods of MVFR conditions
in snow through 21Z before conditions begin to improve. Conditions
are expected to deteriorate at KMTJ, KASE and KEGE this afternoon
as snow showers move in. Conditions will improve from west to east
overnight, although areas of fog may develop in the valleys after
06Z/Sunday and linger through mid-morning Sunday.


CO...Winter Weather Advisory until midnight MST tonight for COZ003-

     Winter Weather Advisory until 2 PM MST this afternoon for COZ006-

     Winter Storm Warning until 5 PM MST this afternoon for

     Winter Storm Warning until 6 AM MST Sunday for COZ009-010-012-

     Winter Storm Warning until 8 PM MST this evening for COZ017>019.

     Winter Weather Advisory until 6 AM MST Sunday for COZ004.

UT...Winter Weather Advisory until midnight MST tonight for UTZ025.

     Winter Weather Advisory until 2 PM MST this afternoon for UTZ022-

     Winter Storm Warning until 5 PM MST this afternoon for UTZ022-

     Winter Weather Advisory until 5 PM MST this afternoon for UTZ028.



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