textproduct: Grand Junction

KEY MESSAGES

- Scattered to widespread precipitation showers and storms continue.

- Flooding concerns are increased for rain-soaked terrain, especially within and adjacent to the southern San Juans.

- A Flood Watch is in effect for southeast Utah and southwest Colorado through 6AM Wednesday. The Flood Watch has been extended for the San Juan Mountains and part of the San Juan River Basin through 6AM Thursday.

DISCUSSION

Issued at 1231 PM MDT Tue Sep 29 2026

ACTIVE WEATHER THROUGH LATE WEDNESDAY EVENING:

The ongoing active weather will continue through late Wednesday evening as a low pressure system slowly moves across the Southwest and east of the Rocky Mountains by Thursday morning. Satellite imagery shows the low is currently centered over northwestern Arizona, which is supporting a transition from southwesterly to southeasterly flow over our area by this evening. Upper level support is limited today while the bulk of forcing and moisture is to our south, so isolated to scattered showers and thunderstorms are expected through this evening, primarily south of I-70. Late this evening moisture and forcing will increase as the low moves eastward, which will further raise precipitation chances south of I-70. Precipitation chances will gradually transition to favor Colorado's higher terrain through the day Wednesday. Wednesday's activity may be more convective, which increases the possibility for periods of heavy rainfall. As such, the Flood Watch has been extended for the San Juans and parts of the San Juan River Basin through 6AM Thursday morning. The Flood Watch remains in effect through 6AM Wednesday morning for the remaining areas of southwest Colorado and eastern Utah. Periods of prolonged or heavy rainfall increase concerns for flooding and flash flooding, respectively, especially in areas that have recently received substantial rain. Rivers may rise out of their banks even after rainfall has ended over an area, so be sure to monitor the forecast and have a way to receive weather alerts.

DRY AND WARMER THURSDAY THROUGH THE WEEKEND:

High pressure moves into our region on Thursday as the low pressure system moves to our east. This pattern shift will bring dry and warmer weather through at least the weekend. High temperatures are forecast to climb from near normal on Thursday to 5 to 10 degrees above normal this weekend.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1140 AM MDT Tue Sep 29 2026

Abundant moisture will lead to continued cloud cover and scattered showers over the region this afternoon. Showers will become widespread this evening south of I-70 with lesser coverage over northern sites. Terrain obscuration will also be widespread leading to areas of ILS to MVFR visibility in adjacent valleys and associated TAF sites. Lower clouds lingering behind the moisture could also lead to MVFR/IFR conditions as stratus and/or fog develops.

HYDROLOGY

Issued at 208 PM MDT Tue Sep 29 2026

Tropical moisture continues to fuel a shield of precipitation drifting north across New Mexico. While areas north of the Four Corners have seen a downward tick in shower coverage, HiRes guidance maintains isolated to scattered showers redeveloping across the Southwest San Juans this afternoon. As a result, expect periods of heavy rainfall due to additional showers with embedded thunderstorms possible. Localized heavy rainfall over already saturated soils will pose a threat to our steep and flashy terrain as well as recent burn scars. Storm activity is primarily favored across the southern tier of the forecast area.

The convective potential wanes after sunset; however, as the closed low lifts towards the Four Corners tonight, another round of showers and thunderstorms redevelops. Embedded thunderstorms and additional rain expected through Wednesday evening maintain our concerns for flash flooding and rises on local rivers until precipitation finally exits the Western Slope Wednesday night.

RFC guidance maintains a second peak at several sites, peaking around midnight due to Wednesday's precipitation. Fortunately, water levels are not anticipated to exceed previous high water marks. That being said, localized flooding and flash flooding continue to pose a threat to our southwestern Colorado communities until remnant moisture from Hurricane Polo and the closed low completely exit our region.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Flood Watch through late tonight for COZ017-020>022. Flood Watch through late Wednesday night for COZ018-019-023. UT...Flood Watch through late tonight for UTZ022-028-029.