textproduct: Grand Junction

KEY MESSAGES

- Scattered to widespread precipitation showers and storms continue through Wednesday evening.

- 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 1030 PM MDT Tue Sep 29 2026

ACTIVE WEATHER WITH FLOODING POTENTIAL THROUGH LATE WEDNESDAY:

A vertically stacked closed low is currently located over central Arizona, resulting in southwest upper level flow over southwest Colorado with easterly wraparound flow at the surface as seen earlier with storm motion. Radar looks quite benign at the moment as we remain in the deformation area but that will change overnight as the low moves eastward, allowing precipitation to wraparound the low across the San Juans. Most precipitation chances will remain south of I-70 through the day on Wednesday. While precipitation has been mostly stratiform under this stratus cloud shield today, we are seeing some convection firing closer to the low and on the edges of the moisture gradient. If we get enough breaks in the cloud cover, more robust convection could develop resulting in heavier rainfall rates. However, if the cloud cover remains prevalent, this could limit the convective potential resulting in a more steady light to moderate precipitation with pockets of locally heavy rainfall. Regardless, Southwest Colorado has already received well over an inch of rainfall in many locations over the last 48 hours so they remain saturated even with rainfall over the past week or two. As a result, the Flood Watch will continue for the San Juan Mountains and San Juan River Basin through 6 am Thursday morning. Periods of prolonged or heavy rainfall increase concerns for flooding and flash flooding, especially in these saturated areas. 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. Most shower and storm activity will decrease in coverage Wednesday evening as the low moves east and drier air moves in behind it from the northwest.

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 /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1124 PM MDT Tue Sep 29 2026

Fairly quiet start to the TAF forecast with precipitation limited to the southern border. However expect this precipitation shield to lift northward through the early morning hours spreading precipitation and lower clouds along the way. MVFR is currently impacting KTEX and this will continue for much of the forecast with these conditions lifting up toward KGUC to KMTJ through the morning. Farther north from KASE to KEGE VFR/ILS appear more likely until showers move by sunrise. Slow improvement comes after sunset on Wednesday though the wet conditions may lead to additional stratus and fog formation by sunrise on Thursday.

HYDROLOGY

Issued at 1030 PM MDT Tue Sep 29 2026

Tropical moisture continues to fuel a shield of precipitation drifting north across New Mexico. 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 until 6 AM MDT Wednesday for COZ017-020>022. Flood Watch through late Wednesday night for COZ018-019-023. UT...Flood Watch until 6 AM MDT Wednesday for UTZ022-028-029.