404
FXUS65 KGJT 202208
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
308 PM MST Mon Jan 20 2025

.KEY MESSAGES...

- Clearing will bring extremely cold temperatures and windchills
  to the region tonight through Tuesday morning. See the Watch,
  Warning and Advisory section for details.

- Temperatures finally begin to moderate during the latter half
  of the week.

- Light snow returns to the northern and central Colorado
  mountains Wednesday. The next chance for significant snowfall
  comes this weekend.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 154 PM MST Mon Jan 20 2025

Clouds have cleared over much of the region early this afternoon
in the wake of the southeast propagating mid-level short wave
trough that moved over the area late last night and earlier
today. While subsidence had brought clearing, there remained
enough instability and moisture to generate some isolated to
scattered snow showers over the Colorado mountains this
afternoon. Meanwhile, temperatures were running colder than
normal across the region with abnormally low readings in the
high, snow covered valleys and mountains.

Per previous discussions, drying and subsidence promise clear
skies across the region tonight which will undoubtedly lead to
strong radiational cooling. Combined with the lingering arctic
airmass which entered the region this weekend, the absence of
clouds will lead to dangerously cold overnight lows/windchills
in the upper Yampa River Basin, Gunnison Valley and Colorado
mountains this evening through Tuesday morning. The current
slate of Extreme Cold Warnings and Cold Weather Advisories
appeared to be on track so no changes made with this issuance.

A transitory positive tilt ridge shifts over the region late
tonight into Tuesday morning which will advect warmer 700 mb
temperatures over the region resulting in milder temperatures
across the mountains. However, lower elevations will find
themselves under a strong inversion which, when combined with
unusually cold lows, will make it difficult to warm during the
day. From late morning through the afternoon, a low amplitude
short wave trough will generate mid and high clouds over the
northern half of the forecast area, but latest models indicated
additional snowfall is unlikely.

However, isolated to scattered light snow showers are expected
to develop tonight as the fast moving short wave trough brushes
the northern Colorado ranges along the Continental Divide. Due
to the limited moisture available this activity will bring very
light accumulations. Overnight lows should continue to run well
below normal, but aren`t expected to be nearly as cold as those
forecast for tonight. The Gunnison Valley comes close to Cold
Weather Advisory criteria overnight Tuesday, however prefer to
let tonight`s lows inform whether additional highlights are
necessary.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 154 PM MST Mon Jan 20 2025

Temperatures, which have been a primary concern in the forecast,
will finally begin to climb back to near normal through the long
term. Northwesterly flow through Friday morning will keep
temperatures cool, but still greater than the extreme cold
temperatures from earlier in the week. On Wednesday and Thursday
temperatures should be 5 to 15 degrees below average for most of the
CWA. On Friday warm air advection will occur as flow shifts to
zonal, due to a trough beginning to dig to our west. Thus,
temperatures should warm back to near or above normal. In
particular, overnight low temperatures on Friday and Saturday
night are currently forecasted to be well above average due to
increased nighttime cloud coverage.

In general, dry weather is expected through most of the long term.
Light snowfall is in Wednesday`s forecast for the northern and
central mountains, but accumulations are expected to be minimal.
Despite some upper-level support from a passing disturbance,
forecasted PWAT values on Wednesday fall around 50% of normal at
most, really limiting any precipitation. Our next notable,
widespread event looks to be this weekend. Both the ECMWF Ens and
GEFS Ens suggest a minimal plume of moisture increasing PWAT values
to around 120% of normal. There is potential for this atmospheric
moisture to coincide with synoptic forcing, but at this point
confidence remains low on impacts as there is significant model
variation regarding how the anticipated trough to our west will
deepen.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1037 AM MST Mon Jan 20 2025

Conditions rapidly improved in the late morning as subsidence
aloft brought clearing and decreased snow showers. However, at
KASE ceilings below ILS breakpoints lingered, but should clear
up by 20Z. Farther south, KTEX was also experiencing some lower
ceilings and the potential for an early afternoon snow shower.
Elsewhere, and beyond 20Z, VFR conditions take over, though
brisk north and northwest winds will impact a number of
airfields across the region.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Cold Weather Advisory from 9 PM this evening to 9 AM MST
     Tuesday for COZ001-007-008-011-021>023.
     Extreme Cold Warning from 6 PM this evening to 11 AM MST
     Tuesday for COZ002-004-005-009-010-012>014-018-019.
UT...None.

&&

$$

SHORT TERM...NL
LONG TERM...GF
AVIATION...NL