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000
FXUS65 KGJT 242354
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
454 PM MST Fri Jan 24 2020

.UPDATE...
Issued at 1226 PM MST Fri Jan 24 2020

Surface obs indicate that dense fog has lifted into a low stratus
cloud deck in the Uinta Basin. A few locations on the slopes of
the Uintas may continue to see dense fog this afternoon, however
visibility is now above 1/4 mile in most locations. Therefore the
Dense Fog Advisory will be expired early.

&&

.SHORT TERM...(Tonight through Saturday night)
Issued at 1210 PM MST Fri Jan 24 2020

The primary weather story in the short term continues to be
persistent low stratus and fog trapped in stubborn inversions
across valley locations of western Colorado and eastern Utah.
Trends in satellite as well as surface obs/webcams early this
afternoon indicate that mixing has eroded a fair amount of the low
stratus in the Yampa Valley including Craig, Gunnison/Uncompahgre
Valley including Montrose, and the Disappointment Valley
including Nucla. Low stratus remains entrenched from Rifle through
Grand Junction and on into much of eastern Utah. Additionally,
low stratus remains entrenched in the Uinta Basin, underneath a
blanket of thickening cirrus clouds aloft. As we are now
approaching peak heating, any inversions that have not mixed
already are unlikely to do so, especially as cirrus cloud cover
thickens aloft through the afternoon and evening hours area-wide.
Forecast soundings indicate potent moist inversions once again
overnight into tomorrow in places such as Grand Junction, Vernal,
Canyonlands, Rifle, and possibly Montrose and Craig.

The other weather event to monitor this evening will be the chance
for isolated snow and light accumulations in the mountains of
central and northern Colorado, as well as northeast Utah. High-res
guidance is in good agreement showing the arrival time of light
snow around or shortly after sunset in the western Colorado
mountains. Eastern Utah high country should see some isolated snow
showers by mid-afternoon. This system is fast-moving and
moisture-starved, and snow accumulations are not forecast to be
very high. An inch or so will fall in most places from the Elks to
the Sawatch, with 2-4 inches possible in the higher terrain of the
Gores, Flat Tops, Parks, and Elkheads. The only valley locations
that may see some snow would be along the US40 corridor where an
inch or so may affect Craig to Steamboat Springs, as well as along
I-70 from Rifle to Vail and the Roaring Fork Valley where an inch
or so of snow is likely by Saturday morning.

Drier air will work in aloft on Saturday late morning and
afternoon, and a snow will not be an issue anywhere after noon.
Stubborn low-level inversions will likely remain in place from
Rifle westward in to much of eastern Utah on Saturday afternoon,
as well as in Vernal and Nucla. Expect low stratus cloud cover to
continue in these locations for the entire short-term forecast
period.

.LONG TERM...(Sunday through Friday)
Issued at 1210 PM MST Fri Jan 24 2020

A new storm system will approach from the west and cross Utah
Sunday, arriving over eastern Utah and western Colorado Sunday
night into Monday morning. Snowfall chances look to increase
across much of the region as this system will dive further south
than the Friday-Saturday system. It still remains shallow however
so the stratus may remain across east-central Utah and west-
central Colorado. There is a little more mid level energy, so
potential does exist to mix out a few locations on Sunday
afternoon, especially up north along the US 40 corridor. Snow
will continue through Monday evening along the western Colorado
mountains and this one may produce a bit more snow here, however
at this time, amounts remain below advisory criteria. A
progressive unsettled pattern continues through much of the coming
week with a more robust, positively tilted trough moving in from
the northwest and across the region Tuesday evening through
Wednesday evening. The upper level jet associated with this one
will take a plunge south of the border into Mexico, so thinking
this will be the one to break those inversions and clear out the
pesky stratus. This system is a bit colder than the previous
shallow shortwaves with H7 temps in the -8C to -12C range. Drier
northerly flow moves in by Thursday with a ridge building out
west. The models are surprisingly fairly consistent through the
forecast period so confidence on timing is moderate to high.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 454 PM MST Fri Jan 24 2020

Another day...another battle of low clouds...fog and passing snow
showers. Besides KCNY TAFs are hanging at VFR/ILS attm but do not
expect things to stay this optimistic through the evening. Big
question will be if/when stratus and or fog returns to some of
the valleys behind this system and confidence extremely low attm.
Plenty of low level mositure remains trapped and so have hedged
for a pessimistic forecast in many areas. Snow will impact the
eastern TAF sites through the evening as well. We be watching
radar...satellite and obs for updates and getting a handle on the
next forecast through the evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

UPDATE...MAC
SHORT TERM...MAC
LONG TERM...MDA/TGJT
AVIATION...TGJT