871
FXUS65 KGJT 302030
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
230 PM MDT Thu May 30 2024

.KEY MESSAGES...

- Chances for isolated to scattered showers and thunderstorms
  remain along portions of the higher terrain each afternoon
  through early next week.

- Temperatures remain above normal this weekend into early next
  week...an expanding ridge aloft next week suggests
  temperatures are likely to climb even higher by midweek.

- The warmer temperatures means runoff will be well underway
  with most major stem rivers showing rises over the next
  several days.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 230 PM MDT Thu May 30 2024

Temperatures have been noticeably cooler since 24 hours ago by
up to 10 degrees in some areas up north in the wake of a cold
front. The front has swept moisture into the southern CWA per
GOES ALPW images and this is where weak convection has been
firing over the past few hours. The threat...along with gusty
outflow winds...will persist through sunset then quickly die
off. Another batch of moisture is already moving on shore in the
PacNW and will arrive for another round of weak convection
tomorrow. Though mainly isolated in nature the storms should
spread to much of the other higher terrain by early afternoon.
CAPE remains minimal which will limit overall updraft strength
but a few gusts over 45 mph have a small probability (<20%) of
occurrence. Cloud cover will be more robust tomorrow with the
arrival of the moisture but temperatures should warm several
degrees over today`s cooler readings and end up near normal.
Looking at the crystal ball these readings are going to feel
cool as we are heading toward the possibility of our first
triple digit reading in the CWA by late next week. This heat
will continue to work over the last of the snowpack and forecast
are for many of the main stem rivers to continue to rise and
possibly peak within this same time frame. The threat of
flooding remains low but both smaller tributaries and larger
river systems will still be running fast and cold. Good for
play...bad for fishing...continue to use caution as we get
through this runoff period.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 230 PM MDT Thu May 30 2024

With a large and relatively stationary trough located over the West
Coast, flow aloft over eastern Utah and western Colorado will remain
zonal to southwesterly through the weekend. This will keep
conditions relatively stable, with temperatures running 5-10 degrees
above normal, and chances for isolated to scattered afternoon
showers over the higher terrain. The trough axis finally pushes
through sometime on Sunday afternoon, with a weak front tracking
across northeast Utah and northwest Colorado. This also happens to
be where the best moisture will be pooled, allowing for some
increased storm coverage over the higher terrain. Main threats with
these storms, as with any during the long term period, will be gusty
outflow winds and lightning.

As this trough passes through eastern Utah and western Colorado, a
piece of energy peals away from the base of the trough near the
California/Baja border. This patch of energy will retrograde off the
SoCal coast and eventually, by midweek, become a cutoff low. In the
meantime, another Pacific low, with an accompanying slug of Pacific
moisture, will move into the Pacific Northwest Monday and will track
east, with its base brushing the northern portions of the CWA
Tuesday afternoon. This will once again lead to an expansion of
shower and storm coverage over the higher terrain, favoring areas
north of I-70. Now, at this point that cutoff low becomes important.
In response to the deepening of this low, an expansive ridge of high
pressure builds into the Southwest. Discrepancies crop up with how
this ridge reaches the Desert Southwest, whether it comes from the
southwest of builds in from the southeast, which then also
influences the placement of the ridge axis. The ensemble and
deterministic GFS favors the solution that builds the ridge in from
the southeast and places the ridge axis as close to directly over
eastern Utah and western Colorado possible. The ensemble and
deterministic EC favors the opposite, with the ridge axis oriented
more southwest to northeast and focused over California and Nevada.
Therefore, the GFS solutions favor higher heights aloft, warmer
temperatures, and places a pool of above normal moisture over the
Four Corners to be recycled in daily convection, while the EC puts
us at the edge of the heat and the moisture plume, leading to a
slightly cooler and slightly drier solution. Blended guidance,
naturally, favors something in between... warmer, with highs 10-15
degrees above normal, but drier, with low-end PoPs confined strictly
to the Divide. But despite all these discrepancies, all ensemble
guidance is placing forecast highs for the late week period in the
top percentile compared to a thirty-year climatology, leading
confidence to a period of unusual heat from midweek on. So strap in,
summer is most definitely on its way.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1135 AM MDT Thu May 30 2024

A few afternoon breezes may cross the 25 mph threshold at
several TAF sites as mixing will be deep in this warm
atmosphere. In addition isolated thunderstorms will be possible
over the southern Colorado mountians with an outside chance of
of a storm impacting KTEX. Gusty winds over 40 mph will be the
main threat. This threat will end near sunset with VFR
conditions holding over the next 24 hours.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...15
LONG TERM...BGB
AVIATION...GJT