764
FXUS65 KGJT 211800
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1200 PM MDT Mon Sep 21 2026

.KEY MESSAGES...

- Mostly dry conditions and seasonable temps on tap for Monday.

- Wetter weather returns to the region by Tuesday, with showers
  and storms possible each day through the end of the work week.

- There is a potential for moderate and heavy rainfall that
  could lead to flooding mainly in the southern San Juans and
  surrounding valleys Tuesday through Thursday.

&&

.DISCUSSION...
Issued at 1142 AM MDT Mon Sep 21 2026

DRY MONDAY:

Quiet weather and seasonable temperatures are expected today.


PRECIPITATION CHANCES RETURN:

On Tuesday a shortwave trough will track over the region. As it
approaches our area increased southwest flow will advect
moisture back into our area. PWATs appear to be 180-200% of
normal for a good portion of the CWA, with the highest values
forecast to be south of I-70 especially near the Four Corners.
Given this moisture and forcing from the wave scattered to
widespread showers and storms are expected. Instability and
shear from the system will support the potential for a few
stronger storms. Also, there could be localized heavy rainfall
in the afternoon. Showers may linger Tuesday night as the wave
tracks over Wyoming and drags a weak cold front through. On
Wednesday the moisture becomes confined to the southeast
portion of the area, so this may allow for the northwest to dry
out. Models are hinting at a subtle wave moving in from New
Mexico on Wednesday into Thursday. It would provide lift and
reinforce the moisture as well therefore precipitation chances
increase once again. The highest QPF for this round is focusing
around the southern San Juans and southern valleys. In fact,
there are indications some spots could get several inches, which
increases the potential for flooding. Rainfall is possible in
the central and northern mountains, but in general the amounts
as lower. Uncertainty increases on whether the moisture gets
pushed out of the area or leaves enough to support showers on
Thursday and Friday. Either way it appears that moisture will
not go far so it will not take much to return.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1142 AM MDT Mon Sep 21 2026

Light diurnal winds are expected throughout the TAF period. Some
mid to high level cumulus will move into the region during the
afternoon. Clouds will increase throughout the morning from the
south and bring scattered to broken cloud cover to southwestern
Colorado and southeastern Utah. Cigs will remain above ILS
breakpoints and VFR conditions will persist.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...TGJT
AVIATION...TGJT