101
FXUS65 KGJT 101052
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
452 AM MDT Thu Oct 10 2024

.KEY MESSAGES...

- Near record highs and dry conditions continue for the next few
  days.

- Moisture increases late this weekend bringing a chance for
  precipitation Sunday.

- Potential for a bigger pattern shift emerges next week with a
  drop in temperatures along with precipitation.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 219 AM MDT Thu Oct 10 2024

High pressure is currently located south of the Four Corners leaving
us under westerly flow aloft. There is still moisture trapped within
the ridge, which rotating around it. This moisture should result in
cumulus clouds over the higher terrain this afternoon. The models
are not indicating enough instability for diurnal showers, but if
one can develop along the Divide rainfall will be rather limited.
High clouds spread over the region today thanks to a system moving
over the Northern Rockies. Near record high temperatures are
expected once again. Although perhaps the clouds will keep things
cooler by a degree or two and prevent any records from being broken.
Patchy smoke is possible across the northwest portions of the
forecast area due to the fire in the Uinta mountains. Lows tonight
should be a touch warmer since the clouds are expected to stick
around. Not much changes with the pattern tomorrow as the system to
our north continues eastward so conditions will be similar to
today.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 219 AM MDT Thu Oct 10 2024

The deterministic models are in general good agreement Friday night
through Sunday with the longwave pattern keeping ridging over the
Rockies and troughing over the Eastern States, and a low pressure
system coming ashore through northern California into the Great
Basin where it stalls as it runs into the ridge. Beyond Sunday the
deterministic models diverge with the GFS having the low in the
Great Basin undercutting the ridge by Wednesday while the
European and Canadian models fill the low as it remains stalled
in the Great Basin. This latter scenario is in better agreement
with the ensemble means which tends to be the safer bet in the
long term. Hence, leaning towards the ensemble solution beyond
Sunday that fill the Great Basin low and keep the ridge in place
along the Rocky Mountains. With the low in the Great Basin,
eastern Utah and Western Colorado come under a south-
southwesterly flow that pulls a moist air mass north out of
southern Arizona into the region by Sunday afternoon with pwats
in the 0.6 to 0.8 inch range, enough to support isolated to
scattered afternoon orographic showers across the higher terrain
of mostly the central and souther mountains with a few
developing as far north as the Flat Tops. With the weak flow
under the ridge, this moist air mass hangs around into mid week,
and with the enhanced dynamics along the boundary between the
low to the west and ridge to the east, look for scattered
showers possible each afternoon across eastern Utah becoming
more isolated farther east in Western Colorado. Much of any rain
from these showers will likely evaporate before reaching the
ground producing gusty outflow winds and little if any
accumulation. Though chances are low at this time, something to
watch on this forecast is the GFS solution with the low
undercutting the ridge and moving over the region, which with
the cooler air aloft may kick off more widespread showers and
thunderstorms across the region Tuesday, some of which could be
stronger storms. Temperatures under the ridge through this
period will remain at near record levels 10 to 15 degrees above
normal, cooling to about ten degrees above normal early next
week with the shower activity. Of course, if the GFS gets it
right, these high temperatures will fall to near normal early
next week as the cold low moves overhead. Stay tuned on this
one.

It does look like change is on the way next week. All the models and
ensembles are in good agreement with a deep cold low pressure system
dropping down off the Bering Sea into the longwave trough over the
Eastern Pacific tomorrow into the weekend where it becomes an open
wave that starts shifting the whole longwave pattern to the east
next week. By mid week we should start seeing significant changes to
our weather as the ridge starts moving out over the Plains and the
longwave trough starts moving into the Intermountain West. By the
end of the week, this will bring unsettled weather to eastern Utah
and Western Colorado and a likely end to the mild Fall weather.
Guidance is picking up on this change with temperatures cooling to
near normal to five degrees above normal and increased chances for
precip in the latter half of the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 451 AM MDT Thu Oct 10 2024

VFR conditions can be expected over the next 24 hour with just
an increase in high cloudiness moving in this afternoon.
Overall winds will be light and follow the typical terrain
patterns.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...KJS
LONG TERM...DB
AVIATION...TGJT