531
FXUS65 KGJT 061142
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
442 AM MST Sat Dec 6 2025

.KEY MESSAGES...

- Moderate to heavy snow rates and strong winds have
  materialized over the Colorado High Country creating hazardous
  travel conditons. Winter Storm Warnings and Winter Weather
  Advisories are in effect through this evening and into Sunday
  morning.

- Unsettled weather continues through the coming work week in
  the northern Colorado mountains with mostly periods of light
  snow showers.

- A general warming trend is expected, but the snow covered
  mountains valleys will see cold inversions set up overnight
  lasting through the days.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 312 AM MST Sat Dec 6 2025

SNOTELs had somewhat plateaued in the north this evening but
have begun to pickup significantly since midnight with the
arrival of the high IVT plume. Webcams up on the Park Range are
verifying this with SNOINCR rates of at least an inch. Better
snow rates have also dropped past I-70 with visibility lowering
at KASE and KGUC in the past hour. Speaking of I-70 webcams from
Rifle eastward are showing deteriorating road conditions which
will continue to impact travel for much of the day into this
evening. Winds are the other component to this storm and we are
just now starting to see some stronger gusts in the Yampa Valley
with Craig gusting over 35 mph and near 45 mph at the Storm
Peak Lab. The core of 45 to 55kt winds at H700 drop south of the
Wyoming border through sunrise and this should bring the threat
of blowing snow to high country through the afternoon before
the gradient begins to relax. Did back off on some of the
outlier QPF numbers (90th percentile) on some of our terrain
looking at various ensemble groups and associated violin plots.
However we are still looking at many of the higher elevation
sites in the northern and central mountains measuring this storm
in feet and with the winds some impressive drifts. Would have
to assume backcountry conditions could be unstable with and
behind this system with high to considerable avalanche
conditions forecast by CAIC. The higher IVT plume will drop
south of the area by this evening with cold NW orographics
becoming the main driver through Sunday morning. The dendritic
layer looks to stay saturated over the northern and part of the
central mountains toward sunrise. Snow-2-liquid rates will
increase closer to 20:1 up north before things wind down through
the morning hours so looking a several more inches of light
fluffy snow over the divide. Did extend the warning for the Park
Range to Sunday morning as a result but some light snow or
flurries are likely to linger over the high peaks through the
day. Otherwise no big changes to the headlines or forecast with
impactful snow/winds over the northern and central mountains and
north facing San Juans expected. Highway 40 and especially the
upper I-70 corridor can expect difficult and hazardous travel
conditions for much of the day.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 312 AM MST Sat Dec 6 2025

By Sunday evening, showers will have mostly ended, though can`t rule
out a stray light orographic shower from residual moisture on the
western face of the Park Range. With the Eastern Pacific high
settling to the south off the Southern California Coast and
continued troughing over the Plains, eastern Utah and Western
Colorado remain under a northwesterly flow with a tight gradient
with H500 winds approaching 80 kts. A shortwave disturbance in this
flow brushes the northern Colorado mountains Monday with light snow
showers and very little accumulation, but expect winds gusting 40-50
mph along and east of the Park and Gore Ranges producing blowing
snow with areas of low visibility. As the high slides south, the
flow up stream becomes more west-northwest bringing a more temperate
maritime airmass to the region with temperatures warming five to ten
degrees by Tuesday and yet another five to ten degrees by Thursday.
A major atmospheric river (AR) starts impacting the Pacific
Northwest Coast Tuesday morning and continues through Thursday with
significant moisture reaching inland to the Rocky Mountains. By
Tuesday evening, integrated water vapor transport (IVT) values in
excess of 300 kg/m/s push into the northern mountains kicking off
moderate showers across the northern colorado mountains with lighter
showers spreading south into the central mountains. With the warmer
temperatures, snow levels start around 7,000 ft, rising to 8,000 ft
Wednesday. Expect moderate shower developing on the western slopes
of rising terrain with rain in the lower elevations and snow higher
in the mountains. With this system, the stronger winds aloft will
mix down gusting 25-35 mph in the lower elevations and 50-70
mph in the mountains with the stronger winds north of the I-70
corridor. Current forecast guidance points to this system having
winter weather highlights for the Park and Gore Ranges, and
possibly farther south, but there is still a lot of uncertainty
with the track of the high and little variation can
significantly change the track of the AR. Stay tuned through the
weekend and by Monday, models should have a better handle on
this system.

The ensemble models are in good agreement with the high to the
southwest opening into a transient ridge and the whole synoptic
pattern shifting eastward bringing a major change in the weather
pattern. This would push all the weather systems to the north and
east bringing an extended warm dry period to the Intermountain West.
The ensembles are wanting to keep the synoptic pattern shifting
eastward which could bring more active weather to the region for the
holiday travel. This is a reach that far out (two weeks!) with very
little confidence, but it will be fun to see how this plays out.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 442 AM MST Sat Dec 6 2025

Snow and/or gust winds of 25 to 35kts will be impacting TAF
sites East of KCAG to KRIL to KTEX line through sunset.
MVFR/LIFR conditions will be possible at times at these
terminals along with stronger wind shear aloft creating mountain
wave turbulence. Lower clouds and passing snow showers will
linger well into the evening and continue to impact KHDN...KEGE
and KASE with periods of MVFR or lower conditions. Improvement
may come late to these TAF sites though ILS conditions may hang
on with widespread terrain obscuration over the higher
mountains likely to continue well into Sunday morning.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Storm Warning until 5 AM MST Sunday for COZ004.
     Winter Weather Advisory until 11 PM MST this evening for
     COZ005-008-009-018.
     Winter Storm Warning until 11 PM MST this evening for COZ010-
     012-013.
UT...None.

&&

$$

SHORT TERM...15
LONG TERM...DB
AVIATION...TGJT