999
FXUS65 KGJT 040604
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1204 AM MDT Wed Jun 4 2025

.KEY MESSAGES...

- Stronger storms will continue to be possible over southern
  portions of Utah and Colorado through the evening with threats
  of larger hail and heavy rainfall rates.

- Showers and isolated storms into the early morning hours
  become more widespread through the day on Wednesday. Localized
  flooding and storm producing small hail will be the main
  threats through the day.

- Unsettled weather remains in place for the remainder of the
  week resulting in below-normal temperatures and a daily
  afternoon thunderstorm threat.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 359 PM MDT Tue Jun 3 2025

As advertised much drier air has filtered into the northern 2/3
of the CWA on northerly flow attached to the large scale trough
over central NOAM. The convergent line between this drier air
and the residual tropical moisture lies across southern Utah to
southwest Colorado where MUCAPE has reached 2000 J/kg. Pockets
of stronger shear in this area has also allowed a few of the
storms to develop updrafts strong enough to support larger hail
according to radar signatures. There is likely some impressive
rainfall rates associated with these storms as well with large
scale ascent coming from the Subtrop jet south of the 4 Corners
and channelized energy also being pulled along from the upstream
low off the SoCal Coast. There should be a downturn in
convection once sunset arrives but at least isolated nocturnal
convection will be possible as the upstream low approaches the 4
Corners from the Southwest. This will back the winds aloft and
keep a strong feed of moisture into the southern CWA at set the
stage for another round of thunderstorms on Wednesday. The
challenge will be the amount of cloud cover lingering from
overnight convection inhibiting heating and leading to less
organized storms. However where more sunshine pops or in the
transition zone between retreating clouds and clear skies
occur...more unstable conditions for stronger storms and
heavier rainfall rates should be expected. Overall the shear
profile looks a bit weaker and updrafts producing moderate to
heavy rainfall rates and small hail would be the favored storm
mode. With heavier rainfall the past few days the threat of
excessive runoff will need to be monitored in the more
organized storms producing the heavier rainfall rates. The upper
low will be shearing in the flow and the energy continuing to
flow through the southwest flow aloft to keep showers and
embedded storms going well into early Thursday. The clouds and
deep moisture will also keep the cooler than normal temperature
trend in place.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 359 PM MDT Tue Jun 3 2025

On Wednesday, the second shortwave trough approaches us from the
Desert Southwest. In the process it will pull deeper moisture back
into the southern half of the area. PWATs values reach 150 percent
of normal up north and as high as 250 percent of normal down south.
As the trough passes over the area it will provide large-scale light
therefore we are expecting another day of scattered to widespread
showers and storms. The timing projected by the models brings it
through during the day, which coincides with peak heating. It there
is any sunny skies then it could allow for enough instability to
produce strong thunderstorms. These storms would be capable of hail
and heavy rainfall. If no instability can materialize then expect
pockets of stratiform with more isolated thunderstorms. Just as that
shortwave exits the western CONUS additional energy drops into the
trough keeping us in west to southwest flow. Also, it appears that
not all of the moisture leaves the region and there will be enough
for showers and storms on Thursday. The pattern looks like it may
become more blocking into the weekend, which means low confidence in
that forecast. This could also lead to a gradual warning trend and
perhaps overall drier conditions. Afternoon convection in the
mountains look possible through the extended.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1159 PM MDT Tue Jun 3 2025

Scattered showers with isolated thunderstorms continue across
southeast Utah and southwest Colorado through the early morning
with KTEX and KDRO seeing potential ILS conditions but overall
VFR is expected to prevail. A thick blanket of clouds is
expanding as far north as the Bookcliffs and Flattops. This
could result in a delay in afternoon convection but storms are
expected to redevelop mainly across areas along and south of
I-70 after 18Z Wednesday afternoon with some stronger convection
leading to brief heavy rain and strong gusty winds. Showers will
expand northward after 00Z into the evening across much of the
area. Most TAF sites include a PROB30 for thunderstorm potential
late this afternoon and evening, with the southern TAF sites of
KTEX and KDRO having higher confidence in prevailing -TSRA.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...15
LONG TERM...KAA
AVIATION...MDA