018
FXUS65 KGJT 082311
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
511 PM MDT Wed May 8 2024

.KEY MESSAGES...

- Snowfall will spread out of the northern Colorado mountains
  into the eastern Utah and southern Colorado mountains tonight
  into Thursday.

- Snow amounts in excess of 6 inches have at least a 60 percent
  probability of occurring over the highest peaks of the eastern
  Uintas...eastern San Juans and Elk mountain over the next 48
  hours...with lesser probability along the travel corridors.

- Unsettled conditions will persist through the weekend along
  with a slow warming trend...however temperatures will remain
  below normal.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 329 PM MDT Wed May 8 2024

Unfortunately winter is not done with us...especially over the
higher terrain over the next several days. The 08/12Z H500 hand
analysis map still showed a healthy Rex Block over Northern
Plains and Canadian Prairies. Satellite imagery through the day
has shown this low shearing apart with retrograding energy now
digging a trough back into the Great Basin. A circulation looks
to close off in the vicinity of the CO/UT line by sunrise on
Thursday. As a result we will see a shift in the snow potential
shift from the northern CO mountains back to the East and South
as this circulation continues to ooze back to the West to end
out the week. Since retrograding...anomalous patterns are so
easily handled by the models that leads to extremely high
confidence in this forecast. None of that last sentence is true.
Wetter and cooler conditons are about the only components of the
forecast that I have confidence in. Feel the models become a bit
saturated with convective feedback over the next few days which
is leading to some excessive QPF bullseyes. However convection
will be a bigger component to this pattern and will likely drive
snow levels down and rates up at times...flashback to yesterday
at this time. Overall however the colder air in the trough is
moderating and we will see slow but gradual warmup over the next
few days. As such will snowfall be much of a factor in the
afternoons...especially at or below pass level...betting on no.
Over the next 24 hours the northern Utah mountains and eastern
San Juan mountains will be the focus for the heavier
precipitation amounts. The former will be under a favorable
northeast flow pattern as the trough digs westward along with
added ascent from the curved jet aloft. Amounts in the high
Uintas exceeding 6 inches have a least a 60% probability but
this is much lower along the travel corridors so attm holding
off on winter highlights there. Meanwhile southerly flow will
be increasing over the southern high plains as heights lower
back here to the West. This will tap into a healthy Gulf of
Mexico tap which will be the main source driving the prolonged
QPF event through the weekend. Much of this source however
arrives West of the divide after this forecast period with the
higher QPF amounts staying on the eastern side thanks in part
to an upslope component. So overall temperatures remain below
normal for Thursday and the increase in moisture/clouds tonight
will limit the threat of widespread freezing conditions tonight.
Best advice remains if travelling through the mountain corridors
to be also be prepared for the threat of compromised road
conditions at times...especially during the overnight hours and
periods of more intense snow rates.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 329 PM MDT Wed May 8 2024

An elongated low pressure center parked over the Great Basin Friday
morning will deliver another round of clouds and surface
precipitation to the West Slope Friday and Saturday...and beyond.
Some model inconsistencies with the moisture tap cast some doubt on
amounts of precipitation we can expect. Warm air advection will keep
snow levels above 9000 feet Friday, but mountain zones can expect
some more snowfall through the day Friday, with the San Juans and
Central Mountains getting another coat of 4-6 inches by Friday
night. Warm afternoon temperatures will likely slow down any impacts
to roads during the day Friday, with exceptions on the higher road
passes(i.e. Vail Pass, Wolf Creek Pass). The low shifts south and
east towards the Four Corners Saturday, which cuts off the Pacific
tap of moisture. Wraparound and remnant moisture will be enough for
additional showers on Saturday, just not to the extent of Friday`s
moisture-rich event. The best concentration of moisture remains on
the San Juans/Central Mountains Saturday, where some additional
snowfall is expected on the higher peaks again. By Sunday morning,
the low/open wave has lifted out of the Rockies onto the Plains and
northwesterly flow returns to the region. This will likely be enough
for some instability and afternoon shower development on terrain
Sunday. Not a complete washout for Mother`s Day, but a few showers
might drift off the hills and deliver some gusty winds and rain.
More of the same can be expected Monday, as we remain under the
northwesterly influence. A weak shortwave ripples through too, so
shower coverage will likely tick up Monday afternoon and evening. A
deepening trough stretching from Canada down into the Plains states
looks to keep us under the northwesterly influence aloft, which will
spell out more shower activity along the Divide Tuesday and
Wednesday. Temperature guidance at the moment keeps things looking
more spring-like with just rain next week. Afternoon highs return to
climatological normal Sunday and push upward to start the week as
models anticipate a strengthening ridge to our west. Some skepticism
remains with regard to precipitation type and high temperatures late
in this forecast. The cooler northwesterly influence and cooling
impacts of clouds and precipitation on the mountains could really
wreak havoc on the current mountain forecast early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 510 PM MDT Wed May 8 2024

Precipitation and clouds will expand through tomorrow morning
and ILS to MVFR impacts will become more probable through the
day. Until then mainly VFR prevails. Easterly winds pick up
during the day as a system passes overhead.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...15
LONG TERM...LTB
AVIATION...TGJT