462
FXUS65 KGJT 302104
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
304 PM MDT Tue Apr 30 2024

.KEY MESSAGES...

- The next in a series of disturbances will bring another round
  of rain and snow showers along with isolated thunderstorms to
  the region from late tonight through Wednesday night.

- Impacts favor northwest Colorado and the northern and central
  Colorado mountains where accumulations are expected to range
  from 3 to 6 inches.

- Cold front associated with this system brings cooler
  temperatures on Wednesday, mainly across the north, along
  with strong gusty winds across the entire region.

- Next system arrives over the area on Friday with the north
  continuing to be favored in this pattern.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 304 PM MDT Tue Apr 30 2024

Showers ended across the northern and central mountains this
morning in response to subsidence/drying on the back side of
the exiting mid-level trough. However, this break appears to be
short-lived as the next trough moves to the Great Basin tonight.
Models indicated overrunning precipitation will develop after
midnight as the flow aloft shifts to the southwest. Combined
with divergence in the right entrance region of the polar jet
over central Wyoming this activity will be confined to areas
north of the I-70 corridor with a slight chance for showers over
the central Colorado mountains.

Showers increase in coverage and intensity, spreading into the
southern mountains Wednesday and Wednesday night as the trough
passes over the area. During this period, mid and jet level
upward forcing will be maximized so mountain snow begins in
earnest, mainly for areas above 8500 feet. The northern and
central mountains can expect 3 to 6 inch accumulations will
locally higher amounts with only 1 to 3 inches expected for the
northwest San Juan Mountains. Looking farther south, the lower
elevations of southeast Utah and southwest Colorado shouldn`t
see any moisture from this system. Meanwhile, passage of the
cold front associated with this system will bring 3 to 5
degrees of cooling for all but the Four Corners area where the
late arrival of the front will be too late to impact highs much.

Showers decrease late Wednesday night, but scattered showers are
likely to persist over the central Colorado mountains and the
northwest San Juans into the early morning hours. Overnight
lows will be markedly colder in the wake of the fron Thursday
morning with lows around 10 to 15 degrees cooler for the
northern and central zones, but only marginally colder for the
Four Corners region.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 304 PM MDT Tue Apr 30 2024

The synoptic pattern open Thursday with ridging off the Pacific
Coast and over the Great Lakes, and a longwave trough in between
over the Western CONUS with a low pressure system anchored over
southern Saskatchewan holding the pattern in place. With the most
recent shortwave that pushed a cold front south through the region
overnight having moved east of the Rockies and out onto the Plains,
the next shortwave system will be dropping into the Pacific
Northwest bringing more unsettled weather to the northern and
central mountains of eastern Utah and Western Colorado Friday. A
deeper, much stronger system drops out of the Gulf of Alaska into
the Pacific Northwest Friday night pushing the ridge that had been
off the Pacific Coast inland, disrupting the synoptic pattern that
has been in place for the past week shifting the longwave trough and
Canadian low to the east. From her on the models tend to diverge on
the track and timing of this next low pressure system with the
European models digging not quite so deep and tracking it farther
north over Wyoming and Montana, while the GFS and GEFS models dig
the low deeper onto California and the southern Great Basin before
ejecting it to the northeast over Utah and northwestern Colorado
into Wyoming Monday into Tuesday. Confidence in the track and timing
of this next major system is low at this point, but models are
indicating a significant atmospheric river (AR) associated with this
system with IVT of 150 to 300 kg/m/s moving up into the region early
next week. Current guidance hasn`t picked up on this moisture as of
yet, so we`ll have to be patient another few days to realize what
this system may have in store for the region.

With that being said, the front that pushes south through the region
Wednesday night look to get hung up in the San Juan Mountains
Thursday.   Temperatures will run five to ten degrees below normal
to the north and near normal in the southern areas through the day.
Lingering orographic showers will continue through the day mostly in
the northern and central mountains with little accumulation. Friday
will see another round of showers in the northern and central
mountains as the next shortwave passes to the north with snow levels
dropping below 8000 feet, but little if any accumulation. Convection
shuts down Friday evening and skies clear as the trough moves east
and the ridge slides in from the west. Saturday will be clear, warm
and dry with temperatures reaching five to ten degrees above normal.
Sunday into early next week will see temperatures fall as the major
system approaches. Look for showers and possible thunderstorms
between Sunday afternoon and Tuesday depending on the track and
timing of this storm. Look for significant precip from this system,
but the details are up in the air at this point. Stay tuned for
updates on this next system.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1240 PM MDT Tue Apr 30 2024

Expect mostly VFR conditions through the TAF period with few to
scattered mid to high clouds over the region and a broken mid
deck moving into the areas north of the I-70 corridor after 06Z.
Ceilings will lower to the north through the morning ahead of
the approaching disturbance with a few light showers developing
after 12Z, becoming more scattered and stronger by 18Z with
isolated thunderstorms possible around 18Z in the northern
mountains and the vicinity of KHDN.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...NL
LONG TERM...DB
AVIATION...DB