341
FXUS65 KGJT 250237
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
737 PM MST Sun Nov 24 2024

.KEY MESSAGES...

- Winter Weather Advisories remain in place for the eastern
  Uintas, Flat Tops and the northern and central Colorado
  mountains through Monday morning.

- An Atmospheric River event impacts the area from Monday night
  through Thanksgiving morning bringing a prolonged period of
  moderate to heavy snowfall to the mountains of eastern Utah
  and western Colorado.

- If you plan to travel over the mountains next week, be aware
  that very difficult, if not impossible, driving conditions
  will be possible.

- If possible, plan alternative routes ahead of time, or delay
  travel if possible until Thanksgiving Day. Stay up-to-date
  with the latest forecast as this potentially significant storm
  draws nearer.

&&

.UPDATE...
Issued at 735 PM MST Sun Nov 24 2024

The snow showers have mostly ended over the Eastern Uinta
Mountains with only a few light showers lingering in this area
this evening. Therefore, decided to cancel the Winter Weather
Advisory for the eastern Uintas. Driving in the Uinta Mountains
remains hazardous due to icy and snowpacked roads.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 355 PM MST Sun Nov 24 2024

The initial surge of Pacific moisture from the Atmospheric River
which has pounded the West Coast over the past several days
arrived over the northern half of the forecast area overnight.
This brought snow, heavy at times, to the eastern Uinta
Mountains overnight while weak overrunning over northwest
Colorado brought snow showers there during the morning. Through
mid-afternoon, snow had spread across the Uncompahgre Plateau
and central Colorado mountains with rain showers along the I-70
corridor.

A short wave trough brushes the northern zones late this
afternoon through early this evening, then moves to the High
Plains during toward midnight. This will drive the cold front
associated with this system farther southward to the southern
UT/CO border by early evening where it will stall. Forcing
associated with the passage of the short wave trough combined
with favorable orographic flow will keep snow going over the
northern and central Colorado mountains through the remainder of
the evening with snow winding down during the early morning
hours. Showers over adjacent valleys are expected to turn to
snow as the colder air filters in bringing some light
accumulations.

Will keep Winter Weather Advisories for the northern and central
Colorado mountains going tonight with an additional 3 to 6
inches of snow expected. Meanwhile, in the wake of the trough
conditions will improve. It appears the the Winter Weather
Advisory for the eastern Uinta Mountains will need to come down
early as little additional snow is expected after 00Z. Expect
overnight lows to be markedly colder across the north where
fresh snow has fallen. Elsewhere, lows should be colder, but not
as appreciably.

Isolated snow showers linger, mainly over the central mountains
of the Continental Divide Monday morning with little additional
accumulation expected. This activity should dissipate before
noon. The remainder of the day will be dry, though after a
partly to mostly sunny morning, clouds will begin to fill in
once again during the afternoon ahead of the next storm.
Afternoon highs will be cooler than those recorded this weekend,
but right around normal for this time of year.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 355 PM MST Sun Nov 24 2024

An impactful Thanksgiving week winter storm arrives Monday night
as moisture from an atmospheric river sends PWAT values surging
over 200 to 300 percent of normal for late November. Models are
in good agreement that the AR will arrive to the Four Corners
region late Monday evening, expanding northeast across eastern
Utah and western Colorado by Tuesday morning. During its
residence, the AR will likely produce significant mountain
snowfall and periods of rain and snow in the valleys.

The potential for 18"+ of snow is high (>70%) for the San Juans,
Grand Mesa, and the northern and central mountains in Western
Colorado. As such, these were the primary areas of interest for
our inaugural Winter Storm Watch issuance for this system which
runs from 5pm Monday night until 5am Thursday morning. Moderate
to major impacts to travel are likely during this timeframe. Be
aware that travel over mountain passes is expected to be very
difficult, if not impossible at times, on Tuesday into
Wednesday.

The main feature of uncertainty with this system is the exit
timing. Currently the ECMWF Ens is 6 to 12 hours faster than
the GEFS at pushing the mositure plume south of the forecast
area. In a scenario where the ECMWF Ens is right, travel
conditions could begin to improve by Wednesday afternoon
compared to Wednesday evening/night in the the GEFS. Keep a very
close eye on the forecast this week, especially if you have
holiday travel plans. Plan alternative routes ahead of time or
prepare to delay travel until after the storm has passed.

Quieter conditions return for Thanksgiving Day into the weekend
with cooler temperatures, especially north of I-70. There is
some potential for light mountain snow in the San Juans on
Friday but confidence is very low at this time. Some model
solutions keep the San Juans dry through the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1045 AM MST Sun Nov 24 2024

Scattered to broken skies can be found across the area this
afternoon and this trend will continue with more broken to
overcast skies moving in. Snow showers will continue for areas
north of I-70 with KVEL, KHDN, KASE, and KEGE having the best
chances to see IFR/MVFR under snow showers over the next
several hours. ILS breakpoints will also be reached at several
TAF sites as clouds continue to thicken and lower. Conditions
should improve after between 03Z to 06Z this evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory until 6 AM MST Monday for COZ004-010-
     012-013.
     Winter Storm Watch from Monday afternoon through late
     Wednesday night for COZ004-009-010-012-013-018-019.
UT...None.

&&

$$

UPDATE...TGJT
SHORT TERM...NL
LONG TERM...KAA
AVIATION...TGJT