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Area forecast discussion
National Weather Service Grand Junction Colorado
1047 am MST Sat Dec 14 2019

Short term...(today through sunday)
issued at 320 am MST Sat Dec 14 2019

Some convective banding moving through this morning across the
area, mainly focused along the northern and central corridor. This
is likely a result of enhanced lift due to this area remaining in
the left exit region of a west to east oriented 150 kt upper level
jet streak. This jet streak looks to remain entrenched across the
area north of I-70 through late afternoon before sagging southward
early evening as a cold front moves southward. Anticipating
enhanced lift over The Flattops and Park Range, including
Steamboat Springs as well. A meso low looks to form over Wyoming
by this afternoon with low to mid level convergence across the
northern mountains and into the Steamboat Springs area (upper
Yampa river basin). This is coupled with a strong area of
frontogenetical forcing. Time heights over Steamboat Springs also
indicate moderate lift through the dendritic zone through the
morning and much of this afternoon. Due to the above factors and
favorable conditions, went ahead and upgraded the advisory over
The Flattops to a Winter Storm Warning and issued a Winter Weather
Advisory for the upper Yampa river basin (coz005) which includes
Steamboat Springs and Yampa.

This frontal band then shifts southward late this afternoon into
the early evening hours with hi-resolution models consistently
showing a band of heavier precipitation setting up over the I-70
corridor by 5 PM, right in time for evening rush hour and ski
traffic. Cold air then follows passage of this cold front and
frontal band with some overrunning potentially occurring over the
Glenwood Canyon. Therefore, also issued a Winter Weather Advisory
for coz008 (i-70 from Glenwood Springs to Eagle-vail) from 2 PM
today until Sunday morning. As the trough axis moves through
Saturday night into Sunday morning, the focus for heavier snowfall
accumulations will shift towards the southern mountains and west
elks. An area of low to mid level convergence sets up over the San
Juans through the west elks in southwest flow from tonight through
much of the day on Sunday before the flow shifts to northwest by
Sunday evening. When this front and trough axis moves southward
this evening, the flow becomes more favorable for the Gunnison
basin, especially Cerro Summit on the western end with a west
flow. The southwest flow and moisture overrunning the cold air
trapped in the Gunnison basin Sunday morning through Sunday
evening should help maintain persistent snowfall in the Gunnison
basin as snow falls through a moist dendritic layer, resulting in
seeder-feeder type environment. Because of this, felt confident
enough to issue a Winter Weather Advisory for the Gunnison basin
as well (coz014) from 5 PM this evening through midnight Sunday
night. Extended the Winter Storm Warning in the west elks (coz012)
until midnight Sunday night as well to match Gunnison and the San
Juans as that convergent signature with overrunning maintains
itself through Sunday evening. Snow will fall in some other Lower
Valley locations as the cold air makes its way southward this
evening into Sunday but not anticipating significant enough
accumulations or persistent snow rates to warrant expanding the
winter weather highlites any further.

Long term...(sunday night through friday)
issued at 320 am MST Sat Dec 14 2019

Snow will continue over the San Juans, west elks and Gunnison
basin through Sunday evening before rates really drop off after
midnight Sunday night as this trough pulls out of the region. Some
light snow may linger over the western Colorado Divide through
Monday morning but amounts should be minimal. Most models indicate
rapid drying taking place on Monday as a brisk northerly flow
takes hold. Cold air remains in place through at least mid week
with dry conditions and valley inversions potentially keeping
temperatures colder, especially where snow cover persists. A weak
trough looks to move across by Thursday, but comes across dry with
an increase in upper level flow and some cloud cover. This will be
enough of a change to potentially mix out some of the lower
inverted valleys where snow cover is not present. The mid slopes
though should exhibit a warming trend by mid to late week with
lower inverted valleys remaining cooler.


Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1037 am MST Sat Dec 14 2019

Snow showers continue to move across western Colorado and eastern
Utah favoring northern portions of the forecast area. A band of
moderate to heavy precipitaiton is expected to impact the I-70
corridor shortly then move southeast this afternoon. This will
result in reduced visibilities epsecially near kege, kril, and
kase for a period of time this afternoon and into the evening in
near high elevation sites. Mountains will remain obscured through
the next 24 hours in many places.


Gjt watches/warnings/advisories...
Colorado...Winter Weather Advisory until 5 PM MST Sunday for coz009-017.

Winter Weather Advisory from 5 PM this afternoon to midnight MST
Sunday night for coz014.

Winter Storm Warning until midnight MST Sunday night for coz012-

Winter Storm Warning until 5 PM MST Sunday for coz010.

Winter Storm Warning until 8 am MST Sunday for coz004-013.

Winter Weather Advisory until 8 am MST Sunday for coz005.

Winter Weather Advisory from 2 PM this afternoon to 8 am MST
Sunday for coz008.

Utah...Winter Weather Advisory until 5 PM MST Sunday for utz028.


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