textproduct: Grand Junction

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.