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000
FXUS65 KGJT 120528
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1128 PM MDT Thu Apr 11 2024

.KEY MESSAGES...

- Unseasonably warm, dry and breezy weather prevails through
  the weekend with high pressure in control.

- Unsettled weather returns next week with cooler temperatures
  and the potential for minor accumulating mountain snow,
  favoring the northern and central mountains.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 245 PM MDT Thu Apr 11 2024

A few cumulus are popping up over the ridges with very dry air
infiltrating the area today as a ridge of high pressure nudges
eastward from the Great Basin with the axis crossing the western
Colorado divide by Friday morning. Overall, sunny to mostly
sunny skies are prevalent which is leading to quite the warmup
today as highs will top out around 5 degrees above normal. This
means 60s for most lower valleys with 70s in the desert valleys
of east-central to southeast Utah, 50s for the higher valleys
and mountain towns of Aspen and Telluride, and 40s for the
mountains. The full sun is allowing for some better mixing with
some breezy afternoon winds in some areas but overall, winds
are on the lighter side of breezy.

Warm air advection kicks in full gear on Friday as the ridge
axis shifts east of the Continental Divide, allowing for
southwest flow to increase the gradient aloft, promote deeper
mixing and advect more warm air from the Desert Southwest. The
fly in the ointment lies in a weak shortwave that will be
ejecting out ahead of a low pressure trough that will edge
closer to the California coastline by Friday night. This
shortwave will increase mid level cloud cover late Friday
afternoon into the evening, and thereby generate some virga
showers which could act to enhance winds locally at the surface.
So not expecting much in the way of precipitation with these
showers since the low levels and sub cloud layer remains very
dry. Winds will already be breezier with gusts in the 20s and
30s in the absence of these virga showers. If the clouds are
more prevalent and arrive earlier in the day, this could impact
how warm we get on Friday. The current thinking is that clouds
will hold off until late Friday afternoon so we should see
plenty of sun and mixing late Friday morning into the early
afternoon to obtain our expected warmup with highs climbing to
15 degrees above normal. We may see our first 80 degree
temperatures for the lower valleys of west- central Colorado,
east-central Utah and southeast Utah. The rest of the valleys
look to be in the 70s with 50s and 60s for our mountain towns.
Speaking of the warmth, some locales may be near or break a few
record highs as our record high for the Grand Junction Regional
Airport is 82 degrees F for Friday and we have 81 in the
forecast. All in all, Friday will be mostly dry, breezy and
unseasonably warm.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 245 PM MDT Thu Apr 11 2024

Southwest flow will be in place aloft on Saturday morning,
ahead of a strong cutoff low off the Northern California coast.
A weak shortwave entrained in this flow will act on some meager
moisture to fire some showers over the mountains during the
morning, as well as keep a few clouds around. With dry air still
entrenched at the surface, little if any moisture is expected
to make it to the ground. Clouds and showers will clear out by
the early afternoon hours as drier air aloft moves in. This dry
air, in association with the abundant sunshine and strong
daytime heating, will lead to deep mixing during the afternoon,
leading to some gusty conditions Saturday afternoon and high
temperatures 5-15 degrees above normal. Despite what models were
suggesting just a few days ago, Sunday now also looks warm,
dry, and gusty as model solutions have slowed down the inland
progression of the California cutoff low. Deep daytime mixing
and a strengthening southwest jet aloft, thanks to the
tightening pressure gradient ahead of the low, will bring gusty
winds of 40-50 mph down to the surface across much of eastern
Utah and western Colorado. No wind highlights are in effect as
yet, but that may change with subsequent model runs. Look for
high temperatures on Sunday to run close to Saturday`s highs.

Precipitation associated with the cutoff low finally reaches
eastern Utah and western Colorado on Monday, with the center of
circulation currently forecast to move over the Four Corners.
While this low was slow to reach us, it will be quick to leave,
with models currently forecasting it ejecting into the Plains by
late Monday night or early Tuesday. This accounts for the low
QPF and snow amounts compared to even just yesterday`s forecast.
Wrap around moisture on Tuesday will bring some extra
accumulations to the highest elevations of the Northern and
Central Divide, but overall this event looks sub-advisory
snowfall and is confined generally above 10000 feet. With cloud
cover and shower activity in the area, highs on Monday will drop
down to near normal, with mid-60s across the desert valleys,
mid-50s for the higher valleys, and 40s for the mountain towns.
A shortwave ridge is progged to move in behind this low on
Tuesday, bringing a brief warm-up with it. Highs will climb
around 5 degrees above Monday`s forecast. While this is going on
in eastern Utah and western Colorado, the next cutoff low will
be dropping south into the Pacific Northwest. Models agree that
this system will be more potent, but disagree with how far south
its influence will reach. Right now, there is less than 50%
confidence that any shower activity will make it into eastern
Utah or western Colorado at all, let alone how much. What does
seem likely is another round of strong, gusty winds as the tight
pressure gradient on the southern edge of this low sits
directly over eastern Utah and western Colorado. While the
northern half of the area may or may not see shower activity,
they will definitely see clouds and cooler conditions on
Wednesday. A sharp temperature gradient is expected to set up
somewhere around the I-70 corridor, with areas to the north
seeing highs a solid 10 degrees below normal, while areas to the
south sit at near normal to slightly above normal values. And
as it stands now, this windy and unsettled pattern looks to
stick around through the end of the week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1128 PM MDT Thu Apr 11 2024

Widespread VFR conditions will prevail through the TAF period.
Some high and mid-level clouds will filter overhead with
isolated high-based showers possible over the San Juans after
18Z Friday. Otherwise, winds will remain light and terrain-
driven overnight into Friday morning before gusts of 20-25 kts
return Friday afternoon. Winds diminish again after sunset.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MDA
LONG TERM...BGB
AVIATION...TGJT