219
FXUS65 KGJT 152312
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
412 PM MST Mon Dec 15 2025

.KEY MESSAGES...

- Unseasonably warm and dry conditions continue through much of
  the seven-day forecast.

- Periods of light mountain rain/snow is possible north of
  Interstate 70 Wednesday through Sunday. The potential for
  minor winter weather impacts is confined to the spine of the
  Park Range.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 231 PM MST Mon Dec 15 2025

Conditions remain quiet today as a ridge sits over us. Skies are
clear and high temperatures continue to sit 10-20 degrees above
normal region-wide. The pattern begins to shift tomorrow though.
Another AR is flowing through the PacNW, and per water vapor
imagery, may be slightly ahead of schedule compared to ECMWF
and GEFS forecasts. The leading edge of this moisture is on a
northeastwards track around the backside of the western CONUS
trough as of now, but over the next 24 hours, deterministic
models are anticipating the upper-level flow to transition to
zonal, if not east-southeasterly through the Intermountain West.
This pulls the stream of moisture southwards into our CWA, but
even then, additional moisture will get caught up on the Sierra
Nevada range. As this pool of moisture is quickly depleted,
little more than cloudy skies will be able to develop.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 231 PM MST Mon Dec 15 2025

Models are mostly in good agreement Wednesday with high pressure off
the SoCal/Baja coast and troughing over the Great Lakes putting
eastern Utah and Western Colorado under a northwesterly flow. A
shortwave system moves in through the Pacific Northwest Wednesday
morning, passing over the region that evening into Thursday morning.
Models diverge on timing with the European and the European ensemble
running six hours behind the GFS and GEFS. OF note, H500 winds go
from 40 kts in the morning to 75 kts by evening with gradient
tightening with the approaching shortwave. Look for winds picking up
through the afternoon and continuing through the evening into the
overnight gusting 30-40 mph generally north of I-70, spreading into
the central Colorado mountains, and gusting 55-70 mph over the peaks
of the northern and central Colorado mountains. This system also has
strong jet support supporting a cold front with a GFS jet core of
155kts+ and the European 175kts+. The left exit region of the jet
passes over the northern and central mountains Wednesday evening
frontal boundary for the GFS and early Thursday morning for the
European. H700 temps drop about 8-10C northwest to southeast across
the region with the surface front only pushing south to the San
Juans. Guidance is only dropping surface temps 5-8F between
Wednesday and Thursday, but we could see drops more in the range of
10-15F should this occur. Atmospheric river (AR) moisture with this
system looks impressive with IVTs over 300kg/m/s, but this is mostly
reflective of the strong flow aloft, and not so much deep moisture.
Pwats remain below 0.6 inches. Current guidance still has light to
moderate snow possible over the Park Range and light snow across the
other northern mountains extending south into the Elk Mountains.
This latest run of the models is showing this system to be a much
stronger system than previous runs though it still lacks moisture,
and with the drastic change from the previous runs, confidence is
low for mountain snow accumulation. Holding off on any headlines
with this system to see the next run of the models has to say. Stay
tuned on this one as it could get exciting.

As the nose of the jet slides east and the right exit region crosses
the region, subsidence will kill any heavier showers, but light
orographic showers may persist over the northern mountains Thursday.
Another shortwave passes to the north Friday evening into Saturday
keeping the tight gradient aloft across the region. Look for gusty
winds over the higher terrain Thursday evening through Saturday. The
AR moisture stays mostly to the north as does the jet and any upper-
level dynamics , but does brush the northern mountains. With a more
zonal flow and warm air advection, snow levels rise to about 8,000
feet with rain falling below this elevation. Again, not a lot of
precipitation is expected from this system with only a slight chance
for minor impacts on Rabbit Ears Pass Friday night and Saturday.

Of interest, the AR pushes south to the LA Basin Sunday to bring
moisture into the Desert Southwest and southern Colorado mountains,
but guidance hasn`t picked up on this yet. Early next week we could
see some showers farther south, but we`ll just have to wait to see.
Otherwise, the weather pattern seems to stay unsettled through the
extended period with weak systems passing every few days.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 412 PM MST Mon Dec 15 2025

VFR conditions are expected to prevail throughout the next 24
hours. Winds should remain light and terrain-driven as well.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...BW
LONG TERM...DB
AVIATION...TGJT