949
FXUS65 KGJT 292352
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
552 PM MDT Sun Jun 29 2025

.KEY MESSAGES...

- Afternoon convection will bring some gusty outflow winds to
  the area, mainly over the higher terrain.

- Deeper moisture moves in midweek bringing increasing chances
  for widespread showers and storms.

- Unseasonably warm conditions remain in place through mid
  week.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 156 PM MDT Sun Jun 29 2025

As expected, increased moisture and daytime heating have allowed
convection to fire over the higher terrain this afternoon. The
18Z Grand Junction sounding reported PWATs of 0.5 inches which
is about a 25% increase from what it was yesterday. Surface
based CAPE is only around 500 J/kg though midlevel lapse rates
of 9 to 10C/km indicate enough instability, along with the
moisture, for this convection. Of note, DCAPE is over 1600 J/kg
and given the dry low levels, this holds so the biggest concern
from any convection will be gusty outflow winds. Speaking of,
upstream in central Utah, a few areas have reported 50 mph gusts
so wouldn`t be surprised to see some of those higher gusts
materialize in our CWA. Radar is also showing plenty of outflow
boundaries across the area further highlighting those dry lower
levels and gusty winds.

For Monday, the deepest moisture drops to the San Juans which is
where CAMs are showing the best chance (50 to 60%) for convection.
Dewpoints will increase by about 10F so some light precip may
actually hit the ground though gusty outflow winds will remain a
concern. High temps through the period will continue to run 5 to
8 degrees above normal for late June/early July.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 156 PM MDT Sun Jun 29 2025

On Tuesday, there will be two main features driving our weather
here. A closed low pressure over the coast of SoCal, and a high
pressure over the Southern Plains. These two system will result in
southerly flow, which will advect deep moisture into the area.
Therefore expect scattered afternoon convection over the higher
terrain perhaps propagating over some of the valleys through
evening. PWAT values around 100-150 percent of normal do support a
chance for localized heavy rain. Strong gusty winds are also
possible with these showers. On Wednesday the low pressure begins to
weaken into an open wave as it moves inland, but moisture advection
continues. Expect another round of afternoon convection, but the
coverage should increase compared to Tuesday. The models have been
fairly consistent with bringing that trough through the region on
Thursday. This wave should provide some lift, which happens to
coincide with the peak moisture advection. PWAT values could reach
150-250 percent of normal. This increases the chance for heavy rain
and overall storm coverage. Timing of the wave and morning cloud or
existing showers will dictate storm intensity that afternoon. The
potential for heavy rain and flash flooding could be maximized
Thursday afternoon through the evening if conditions line up
correctly. The models have been consistent with showing a dry air
intrusion behind the departing wave on Friday. Although there are
model differences regarding how much moisture will be left if any to
support afternoon convection. They tend to overdue the drying in
these situations, so hesitant to say dry everywhere. As of now it
appears showers and storms still look possible somewhere in the
forecast area Friday afternoon and evening. Best chances will be in
the mountains as always. The exact location, coverage and strength
of storms is unknown at this time. Details for the weekend are murky
right now, with some models showing a lot of dry air and others
showing enough moisture for showers.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 532 PM MDT Sun Jun 29 2025

Expect VFR conditions and generally light terrain driven winds
through the TAF period. Isolated showers and thunderstorms will
develop over the higher terrain after 18Z with more scattered
storms favoring the Divide. These storms will be capable of
producing strong downburst winds gusting 25 to 45 kts.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...TGR
LONG TERM...KJS
AVIATION...DB