909
FXUS65 KGJT 081839
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1139 AM MST Fri Nov 8 2024

.KEY MESSAGES...

- Periodic light snow continues along the Divide through
  Saturday. Minor impacts to travel are possible.

- Dry weather returns this weekend through early next week with
  temperatures returning to near-seasonable levels.

&&

.UPDATE...
Issued at 811 AM MST Fri Nov 8 2024

Updated the short term forecast through the morning hours to
account for the sunrise surprise light snow that is occurring
over the Grand Valley. None of the models picked up on this
snowfall this morning but the latest hi-res HRRR and NAMNest are
starting to initialize with the current conditions and adjust.
Outside of the Grand Valley, low clouds are occurring with this
band as well as some low valley fog in places. So, thinking this
snowfall over the Grand Valley is a result of moisture
overrunning the temperature inversion in place over the Grand
Valley, causing light snow to precipitate. The band of clouds is
moving from east to west and should clear the Grand Valley by
late morning. Cannot rule out light snow showers or flurries
with this band across the rest of western Colorado or eastern
Utah where it is tracking, so updated forecast to include the
mention of light snow showers. Roads remain wet in the Grand
Valley and do not anticipate much in the way of accumulation. It
will impact visibility though if you are driving in it but rates
remain very light with snow melting as it hits the pavement.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 302 AM MST Fri Nov 8 2024

The low pressure system responsible for the most recent bout of
winter weather is currently located near the southern Arizona/New
Mexico border. It is projected to propagate northeastward
across eastern Colorado before finally ejecting into the Plains
this weekend. As it does so, wrap-around flow will result in
light, fluffy snow showers and a dusting to a few inches of
accumulation along and adjacent to the Divide. Reduced
visibilities and minor impacts to travel are likely while it is
actively snowing but we are not anticipating any notable
disruptions on the Western Slope as this system departs the
Intermountain West. Temperatures remain about 10 degrees below
average across the forecast area today with a gradual warm up
towards seasonal temperatures beginning on Saturday.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 302 AM MST Fri Nov 8 2024

A ridge of high pressure develops over the region from Saturday
night into Sunday in the wake of the storm which has dogged the
forecast area since early this week. As a result, temperatures will
return to near normal levels across the region due in equal parts to
warm air advection and increased solar insolation. Milder, dry
conditions continue into Monday, though a fast moving mid-level low
pressure trough will drive the ridge axis to the east. For this
portion of the long term forecast models were in strong agreement
and forecast confidence is high.

However, confidence becomes diminished during the most consequential
stretch from Monday night through Tuesday night. During this time,
ensemble clusters showed great variability. The discrepancies have
less to do with timing of the trough passage than with the amplitude
of the trough itself. In the operational runs, the Canadian and
ECMWF were similar and both indicated a deeper, sharper trough which
drives a well defined cold front eastward across the forecast area
Tuesday morning. Strong upward forcing, surface convergence along
the front, and orographic lift would result in the high likelihood
of precipitation over the mountains and northwest Colorado plateau
with with snow lingering in northwest flow over the northern
Colorado ranges Tuesday night with this solution. In contrast, the
latest operational GFS most resembled the first cluster in the grand
ensemble which suggested a much lower amplitude trough will push
across the area on Tuesday with a poorly defined cold front which
eases southward and stalls near the I-70 corridor Tuesday afternoon.
In this solution, precipitation chances are more limited and largely
confined to the Elkhead and Park Mountains Tuesday afternoon and
evening. To confuse the issue further, the ECMWF used in the cluster
analysis is time lagged, so it doesn`t include the latest run which
may mean that it`s not capturing a developing trend. Fortunately,
the NBM seemed to have a foot in both solutions and thus indicated
likely showers over the northern mountains with less chances over
the central Colorado ranges. However, not much cool down was
indicated which speaks more to the GFS solution. There`s still
plenty of time for this to get sorted and hopefully we`ll get better
clarity with later runs.

Fortunately, Wednesday and Thursday appeared uneventful regardless
of model solution with weak ridging developing in the wake of
Tuesday`s trough. Meanwhile, temperatures were indicated to return
to near normal levels and may even rise higher later in the
week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1134 AM MST Fri Nov 8 2024

Scattered light snow showers will continue along the Divide at
times, mainly impacting KGUC, KASE and KEGE this afternoon and
overnight. CIGS will linger near or below ILS breakpoints at a
few sites as this system moves east of the area tonight with
some lingering showers up north through Saturday morning. Areas
of fog are possible overnight in lower elevations where recent
moisture occurred. The rest of the area outside of showers will
see MVFR CIGS with VFR conditions across eastern Utah and
portions of western Colorado away from the higher terrain. Winds
will generally be light and terrain driven.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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