Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 290445
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
945 PM MST Mon Nov 28 2016

.UPDATE...
Issued at 945 PM MST Mon Nov 28 2016

Few bands of heavier snowfall shifting south across western
Colorado this evening. Numerous reports of snowfall in the 1 to 2
inch range from Grand Junction east to Rifle. The heavier snow
along this corridor has shifted south and will be impacting Delta
and Montrose through midnight and the Northwest San Juans through
late tonight. Situation setting up for heavier snowfall near and
just south of Ouray in the Uncompahgre Gorge, which is discussed
in more detail below. Adjusted POPS to fit current conditions with
no adjustments to highlights at this time.

&&

.SHORT TERM...(Tonight through Tuesday night)
Issued at 249 PM MST Mon Nov 28 2016

After a brief lull this morning, snow showers picked up again
late this morning as the next disturbance approached from the
northwest. Snowfall is expected to increase in intensity across
the mountains and higher valleys where highlites are in effect
through Tuesday morning, with mountains being frequently obscured
through the period as this disturbance moves through. An
additional 4 to 10 inches of snow is expected in these mountain
areas with the higher valleys expected to see an additional 2 to
5 inches of snow (i.e. Craig, Meeker, Steamboat, Gunnison, I-70
from Glenwood to Avon). Added the La Sals and Abajos in southeast
Utah to a Winter Weather Advisory in effect through Tuesday
morning, as enhancement works south over this area and the
northwest flow orographics favor the La Sals and to a lesser
extent, the Abajo mountains. Time heights over the La Sals
indicate strong and deep omega (vertical lift) through a saturated
dendritic layer for efficient snowfall this afternoon and evening.
As far as the lower valleys are concerned, some light snow did
occur today in Grand Junction, Cortez and Durango to name a few
places. Snow was light and brief as showers are fairly convective
and scattered across the valleys. Webcams indicate roads remaining
wet with little accumulation on grassy surfaces, so impacts are
minimal. Time heights over some of these lower valleys show weak
omega/lift and very brief duration of that, so do not anticipate
adding any lower valleys to the highlites with minimal accumulations
expected on grassy surfaces.

As the backside of the large upper level trough moves through
tonight, the H7 winds will shift to a more north-northwest to
northerly direction. The disturbance will also shift towards the
central mountains and southern mountains as this happens for some
enhanced snowfall. This flow tends to favor the Uncompahgre Gorge
area of the northwest San Juans (Highway 550 from just south of
Ouray to Red Mountain Pass). Looking at time heights in this area,
decent lift through a saturated dendritic layer takes place late
this evening through Tuesday morning, which signifies the
potential for locally higher snowfall amounts in the Gorge.
Increased amts through this area into Tuesday morning. The winter
highlites for the south will drop off Tuesday morning with the
northern and central mountains and higher valleys remaining
through noon Tuesday as they will still see snowfall in favored
north-northwest orographics as the disturbance and upper level
trough exit the region. Some light snowfall may linger through
Tuesday afternoon but additional accumulations and impacts appear
to be minimal as drier air begins to work in from the west by
Tuesday evening with some low clouds hanging around the peaks.

.LONG TERM...(Wednesday through Monday)
Issued at 249 PM MST Mon Nov 28 2016

A shortwave ridge of high pressure will slide over the region on
Wednesday for a fairly quiet day weather wise. Temperatures will
remain below seasonal as cold air remains in place from the
previous storm system. Another disturbance is expected to drop in
from the northwest Thursday afternoon through Friday, but models
are not in agreement with the details. The GFS drops the upper low
circulation into Utah by Thursday evening with southerly flow
showing some enhancement in snowfall over northeast Utah and
northwest Colorado. This low then dives south into Mexico by
Friday and splits from the main trough, leaving our CWA in the
deformation zone which would limit any significant snow at this
time. The ECMWF on the other hand brings this system across as an
open wave and never splits the cutoff low. Timing is similar in
terms of precipitation with northeast Utah and northwest Colorado
being favored so kept slight chance to chance pops in for this
period due to low confidence in the details. Dry air then works in
from the northwest Friday afternoon and evening with a ridge of
high pressure building over the eastern Pacific (just off the
west coast) by the weekend. Dry weather is expected through the
weekend with the chance of precip increasing towards Monday as
another disturbance drops in from the Pacific Northwest and moves
across the northern Rockies, clipping the northern mountains.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 945 PM MST Mon Nov 28 2016

Areas of snow will continue across the mountains of western
Colorado and southeast Utah tonight. The heaviest snowfall will
shift south into the San Juan Mountains by 08z with snow gradually
tapering off from north to south after sunrise. Expect mountain
obscuration to continue with CIGS remaining at or below ILS
breakpoints. VSBY will also be reduced in areas of snow and blowing
snow with IFR conds expected. Breaks in the CIGS arrive by midday
Tuesday with VFR conds returning to eastern Utah and the lower
valleys of west central and extreme southwest Colorado by
afternoon and to other sites by Tuesday evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 6 AM MST Tuesday for COZ014-017.

     Winter Storm Warning until noon MST Tuesday for COZ004-009-010-
     012-013.

     Winter Storm Warning until 6 AM MST Tuesday for COZ018-019.

     Winter Weather Advisory until noon MST Tuesday for COZ002-003-
     005-008.

UT...Winter Weather Advisory until 6 AM MST Tuesday for UTZ028.

&&

$$

UPDATE...JDC
SHORT TERM...MDA
LONG TERM...MDA
AVIATION...JDC



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