838
FXUS65 KGJT 240125 CCA
AFDGJT

Area Forecast Discussion...CORRECTED
National Weather Service Grand Junction CO
625 PM MST Sat Nov 23 2024

.KEY MESSAGES...

- A weak disturbance will tap into the increased moisture
  bringing snow to the higher elevations of northern portions of
  UT and CO tonight through early Monday morning.

- Winter Weather Advisories have been issued for the eastern
  Uintas, Flat Tops, and northern mountains for 6 to 12 inches
  of snow through Monday morning.

- After shifting south of the area Monday night, the AR lifts
  northward and will bring prolonged periods of heavy mountain
  snow Tuesday through Thanksgiving Day. Significant snowfall is
  very likely.

- If you have to travel over any mountains passes next week, be
  aware that very difficult, if not impossible, driving
  conditions are expected. Plan alternative routes ahead of time and
  stay up-to-date on the latest forecast.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 254 PM MST Sat Nov 23 2024

Dry and mild conditions continue for the rest of the afternoon with
partly to mostly sunny skies. A weak upper-level disturbance arrives
late tonight into tomorrow leading to snow chances across far
northeast Utah, northwest Colorado, and the northern and central
mountains. In the latest model guidance, snowfall amounts have
fallen slightly across the eastern Uinta Mountains and increased
slightly across the northern and central mountains. A Winter Weather
Advisory remains in effect for the Eastern Uintas above 8000 feet
from midnight tonight until midnight tomorrow night, and for the
Northern Mountains and Flat Tops from 6 AM tomorrow until 6 AM
Monday. If snow amounts in the central mountains continue to trend
higher, CO zones 10 and 12 (central mountains) may need to be added
to the Advisory.

The bulk of the snow is expected to fall during the day tomorrow,
but additional snowfall may occur through early Monday morning along
the Divide. Expected snowfall totals are as follows: 4-6" in the
Eastern Uintas, T-2" in the northern valleys, 6-12" in the northern
mountains, and 3-6" in the central mountains with locally higher
amounts possible. Winter driving conditions are likely from 6 AM
to 6 PM in the Uintas and northern mountains, and from noon to
midnight tomorrow night in the central mountains. Alongside the
accumulating snowfall, gusty winds in the higher terrain could
lead to blowing snow and reduced visibilities tomorrow afternoon.
Use caution if traveling!

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 254 PM MST Sat Nov 23 2024

Medium range models continued to advertise a significant winter
storm to impact the region in the days leading up to Thanksgiving.
Model consensus appeared better than average, especially between GFS
and ECMWF 12Z/Sun runs.

As mentioned in previous discussions, Monday will see a bit of a
lull between the Sunday/Sunday night storm and the impending
moisture surge associated with an Atmospheric River (AR). Height
fields showed a low-amplitude ridge over the area with weak
overrunning in the 700-500 mb layer. A few lingering showers are
expected over the central Colorado mountains Monday morning,
otherwise overrunning is likely to yield just virga and perhaps a
few flurries over the peaks during the afternoon as the AR stream
remains south of the forecast area. Meanwhile, temperatures are
expected run a handful of degrees above normal due to weak warm air
advection beneath the ridge.

The AR lifts north Monday night and will flow over the area through
Wednesday evening. During this time, levels of integrated vapor
transport and specific humidity will reach the 95-99.5th percentile
relative to climatology from Monday night through Wednesday, or more
simply put, it will be about as wet as it has ever been for this
time of year. Modest mid and upper level forcing combined with
favorable westerly orographic flow is expected to bring prolonged
periods of snow to the mountains. Snowfall rates are expected to
reach their peak Tuesday night into Wednesday morning as the low off
the coast of the Pacific Northwest moves over the area as a short
wave trough. Subsidence on the back side of the trough suggests
conditions could be improving during the afternoon Wednesday. Given
the high levels of moisture, expect most mountains from 9,000 feet
and above will be measuring snow in feet by the time the storm comes
to a close early on Thanksgiving Day. Undoubtedly, this system is
going to make it difficult for those traveling Tuesday and Wednesday
ahead of the holiday. As things stand right now, delaying
travel until Thanksgiving Day would be optimal. That said, the
NBM seemed to be holding onto PoPs from earlier runs on
Thanksgiving and expect as the holiday draws nearer those shower
chances will decline. However, for those planning to return
home on Friday, the weather looks good as dry northwest flow
behind the trough promises quiet weather to end the week.

Temperatures hover near normal during the early phases of the storm
Tuesday and Wednesday, but will dip by 3 to 8 degrees behind the
trough and its associated cold front on Thursday and Friday.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 440 PM MST Sat Nov 23 2024

High clouds are currently streaming north of I-70 and will
increase through the evening and expand further south. VFR
conditions will prevail for much of the area with LLWS present
due to increasing winds aloft and lighter surface winds. Winds
mix down by Sunday afternoon with gusty winds across much of the
area. Showers are expected to favor areas north of I-70 after
12Z Sunday with KHDN and surrounding northern mountains standing
the best chance of MVFR CIGS and VSBY due to shower activity.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory from 6 AM Sunday to 6 AM MST Monday
     for COZ004-013.
UT...Winter Weather Advisory from midnight tonight to midnight MST
     Sunday night for UTZ023.

&&

$$

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