Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 160421
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
921 PM MST Thu Feb 15 2018

.UPDATE...
Issued at 912 PM MST Thu Feb 15 2018

Light snow continues to fall over most of our higher mountains in
western Colorado as lingering moisture gets squeezed out in
favorable orographic flow. Additional snowfall amounts through
midnight will be light, but still sufficient to cause travel
impacts. As a result, plan on keeping all mountain highlights in
place with the exception of the Uncompahgre Plateau in west-
central Colorado. Will also be dropping the high valleys near
Gunnison and Pagosa as only isolated snow showers anticipated
through the remainder of this evening. Clearing and cold
conditions still anticipated later tonight.

&&

.SHORT TERM...(Tonight through Friday night)
Issued at 323 PM MST Thu Feb 15 2018

Models were consistent in moving the cold front to near or just
south of the Hwy 160 corridor in southwest Colorado and just north
of the state border in southeast Utah by 5 PM MST this evening.
Concurrently, the mid-level low pressure trough axis driving the
front southward was shown to extend southwestward from Rock
Springs, WY to Las Vegas. The trough is forecast to shift east-
southeast during the evening, passing east of the Continental
Divide by midnight. Mid-level upward forcing, favorable, but
weakening, westerly ridge-level winds and lingering moisture will
sustain widespread snowfall for the Colorado mountains through the
evening. Consequently, will continue current highlights. However,
dry air fills in quickly over eastern Utah and western-most
Colorado, so will drop the Winter Weather Advisories for the La
Sal and Abajo Mountains and the Uncompahgre, Roan and eastern
Tavaputs Plateaus with this package. Will continue with the
advisory for the Gunnison Valley despite temperatures in the upper
30s at KGUC as concern is with the higher elevation Cerro Summit
area on the western end of the valley. The cold front is just west
of the area and expect snow to pick up there shortly.

Subsidence and drying dominates during the latter part of the
night with just isolated to widely scattered light snow showers
lingering over the peaks along the Divide in the early morning.
Latest highlights end at midnight and this still appears
reasonable. Clearing in the subsident region in the wake of the
trough will bring colder temperatures tonight with readings
falling below freezing for all areas with some single digits and
low negative values in high snow covered valleys.

Friday will begin with mostly sunny skies across the region, but
an approaching shallow disturbance in the northwesterly flow will
bring increasing clouds and possibly a few light snow showers to
the northern Colorado mountains Friday afternoon. Clouds will be
thinner across the south with no chances for precipitation.
Afternoon highs will be cooler and close to seasonal norms. Snow
becomes likely over the Elkhead and Park Ranges with scattered
snow showers over the Gore, Flat Top and Elk Mountains. Expect dry
conditions to the south and west with partly cloudy skies.
Overnight lows Friday night should be a bit milder, especially
across the north where cloud cover will limit the loss of surface
long wave radiation.

.LONG TERM...(Saturday through Thursday)
Issued at 323 PM MST Thu Feb 15 2018

Dry and mild weather is expected to continue this weekend with
scattered light snow showers becoming possible late Sunday
afternoon over the Elkhead and Park Mountains. Models still
predicting a prolonged period of unsettled conditions beginning
Sunday night and continuing through much of Tuesday. The heaviest
period of snow is expected to occur Monday and Monday night as a
fairly energetic mid-level low pressure trough sweeps from the
Great Basin eastward across the forecast area. Some differences
apparent between the GFS and the ECMWF with the latter digging
deeper and therefore maintaining showers longer into Tuesday than
the GFS. For Wednesday and Thursday the forecast area will fall
under the col region between a closed low off the California coast
and a broad trough over the northern Rockies. Models struggle with
this setup so difficult to put much detail in these late periods
where there will be a chance for poorly organized showers, mainly
over the higher terrain.

Weekend temperatures are still expected to be well above normal
with highs on Sunday reaching levels close to 15 degrees above
normal for some locations. The storm system which moves through
early next week will drive temperatures back to near normal levels
with the coolest temperatures Tuesday. Expect temperatures to
moderate Wednesday and Thursday, rising to between 5 and 10
degrees above normal across eastern Utah and western Colorado.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 525 PM MST Thu Feb 15 2018

Scattered snow showers will linger over the mountains of western
Colorado through 04Z this evening before ending for the night.
Expect areas of MVFR to LIFR CIGS and VSBYS in the vicinity of the
showers with frequent obscuration to the mountains. Isolated
valley showers are expected with occasional CIGS dropping below
ILS breakpoints with even some MVFR and IFR conditions possible.
Conditions improve from west to east overnight with VFR pattern
returning for Friday.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until midnight MST tonight for COZ018-
     019.

     Winter Storm Warning until midnight MST tonight for COZ004-009-
     010-012-013.

UT...None.
&&

$$

UPDATE...JDC
SHORT TERM...NL
LONG TERM...NL
AVIATION...JDC



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