textproduct: Grand Junction

KEY MESSAGES

- Isolated showers and seasonable temperatures to start the work week.

- Widespread rain returns Wednesday through Friday.

- The potential for flooding increases on Thursday and Friday especially for portions of southeast Utah and southwest Colorado.

- Rainfall amounts in the southern mountains range from 1-3 inches with locally higher amounts possible in the San Juans.

DISCUSSION

Issued at 1112 AM MDT Mon Oct 19 2026

ISOLATED SHOWERS AND SEASONABLE TEMPS TO BEGIN THE WORK WEEK:

Broad southwesterly flow will dominate the start of the work week, maintaining moisture advection across the region. Expect a continuation of cloud cover along with isolated showers through Tuesday. Modest warm air advection will nudge high temperatures closer to seasonal normals despite the increased cloud cover. While localized breezy conditions could accompany collapsing showers, organized convection is not anticipated.

WIDESPREAD RAIN AND FLOOD POTENTIAL LATE-WEEK:

By Wednesday, a strong low pressure system drops southward along the California coast, while an upper level jet noses into the Four Corners region. These two features will work in tandem to bring remnant moisture from what is now Hurricane Trudy into the region, bringing the return of widespread precipitation chances. Initial model solutions depict the most likely time period for widespread showers to be Wednesday night through Thursday night. It is also important to note that a large majority of the precipitation from this system will fall as rain, with the pool of colder temperatures staying well north of the forecast area. As a result, snow levels will remain high, generally at or above 12,000 feet. Given the prospect of high-elevation rain falling onto antecedent snowpack and saturated soils from last week's precipitation, flash flooding and hydrologic impacts will be monitored closely as the system progresses. The highest amounts of rainfall are currently showing up in the southern mountains where 1-3 inches of rainfall are possible. The San Juans look to take the brunt from this system so locally higher amounts are possible. In fact, some of the river forecasts in that area are reaching flood stage. Ensemble guidance supports PWATs upwards of 250-300% of normal, providing another strong signal to monitor for potential impacts. Keep in mind that the forecast remains fluid this far out, and key details may shift over the coming days. Stay tuned for updates.

Precipitation chances continue into Friday afternoon, though coverage will gradually taper off. Meanwhile, the low pressure system will be absorbed into the main flow, driving a frontal passage through the area. This will bring cooler temperatures on Friday, dropping highs by 5 to 10 degrees compared to Thursday and potentially taking overnight temperatures back below freezing.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1143 AM MDT Mon Oct 19 2026

Mid and upper level ceilings continue to drift across the region. Most terminals remain in non ILS scenarios. However, some isolated rain showers could reflect negatively on ceilings this afternoon. Included TEMPO conditions at several terminals to account for these occurrences. Cloud cover is expected to remain in place overnight to close out this TAF period. For now, it looks like non ILS ceilings for the majority of terminals, but some adjustment may be required for mountain terminals with lower criteria.

GJT WATCHES/WARNINGS/ADVISORIES

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