725
FXUS65 KGJT 140018
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
618 PM MDT Sun Sep 13 2026

.KEY MESSAGES...

- Shower and storm chances increase today, with higher chances
  overnight into tomorrow morning.

- There is a chance for strong storms over the next few days
  capable of producing hail, gusty wind and heavy rainfall.

- Moderate to heavy rainfall could lead to localized flash
  flooding, rockfalls and mudslides at times this week.

- Daytime highs today will be 5 to 10 degrees above normal,
  before a shift to cooler temperatures by Monday onward.

&&

.DISCUSSION...
Issued at 1138 AM MDT Sun Sep 13 2026

COOLER AND WETTER PATTERN THIS WEEK:

Residual moisture and daytime heating will result in terrain-driven
showers and storms this afternoon and evening. The jet associated
with a low pressure in the PacNW has spread over the region. This
means there is some shear present, which could support a few
stronger storms, especially across the northwest half of the CWA.
This evening there should be a transition to more stratiform with
embedded storms.

As that low pressure passes to our north southwest flow will advect
a pocket of deep moisture into the area tonight. PWAT values peak
over 200 percent. Therefore expect the coverage of precipitation to
increase during this surge. The high-res models focus showers north
of I-70 early in the night then south of I-70 late in the night,
which may be due to upper level jet forcing and a weak front.
Periods of moderate to heavy rain are possible and could result
in localized flooding, rockfalls and mudslides. Widespread
showers are expected south of I-70 tomorrow morning, while the
north starts clearing out. The moisture may somewhat decrease, but
it will still be sufficient for redevelopment through out the day.
The intensity and coverage will depend on the instability. So
places that clear out have higher chances of storms in the
afternoon. The jet will still be overhead so some storms may
become strong to severe.

The area remains in southwest flow aloft as the first low pressure
tracks over the Midwest and another low drops into the PacNW.
This will ultimately keep the moisture in place through at least
mid week, so expect the chances for showers and storms to
continue. On Wednesday the models are hinting that a subtle wave
moves in from the southwest. If this were to happen it would
certainly be a focus for showers and storms especially given the
moisture will still be around. Late in the week, the models are
now agreeing that the second low pressure cuts off in the PacNW
and northern Great Basin. Model performance is typical poor for
these cut off lows, mainly how long they stick around. This
lowers confidence in the forecast late in the period. As it
stands now though this period looks to be active due to the low
pressure and moisture.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 610 PM MDT Sun Sep 13 2026

Isolated to scattered storms will continue this evening,
becoming more widespread during the overnight period. Localized
heavy rainfall impacting visibility along with lightning and
gusty outflows will be the primary threats for aviators. MVFR
conditions may be possible where visibilities deteriorate. Winds
will remain breezy with gusts 25 to 35 mph this evening, and
some locations holding on to the higher speeds well into the
overnight period. Precipitation chances will continue to be
around for much of the day on Monday as well so included PROB30
groups for Monday afternoon.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...BS
AVIATION...TGJT