textproduct: Grand Junction

KEY MESSAGES

- Showers and thunderstorms on the terrain favoring northeast UT and northwest CO this afternoon, with more isolated coverage along the southern Divide and San Juans.

- A frontal boundary could deliver some additional showers Tuesday and Wednesday next week.

- A warming trend will continue through the week. Triple digits will remain confined to the Four Corners and low desert valleys.

DISCUSSION

Issued at 1100 AM MDT Sat Aug 15 2026

A drying trend will begin to erode some of the stronger moisture along the UT and CO state line today. Satellite water vapor depicts a plume of drier southwest flow invading this afternoon. Cumulus fields have sprouted on the terrain of the West Slope in the sunny conditions. This will produce a few showers and thunderstorms this afternoon, but coverage will be more abbreviated than previous days this week. Hi res models are favoring the Uintas and the terrain of northwest CO for convection this afternoon. A few showers will still spring up on the southern Divide and the San Juans, but dry air will definitely pose some inertia for these showers. This will also limit the impacts of heavy rain, as flash flooding is not expected to materialize either. Showers decay quickly this evening as drier air intrudes and afternoon heating quickly diminishes. Temperatures will trend near normal this afternoon and Sunday.

The new work week starts off warm and mostly dry with some near zero precipitation chances on the mountains. A weak frontal boundary settles into the northern Great Basin Tuesday and Wednesday. This could bring winds up a bit for our northern counties Tuesday. Relative humidity values tend to stay above critical thresholds for fire weather and winds are not particularly strong either. More widespread shower activity returns Wednesday beneath this frontal activity. PWAT values trend around 140 percent of normal north of the Colorado River and taper to near normal down south. These are ample values for a few stronger showers if we can line up some forcing along the front, which glances our northern counties Wednesday afternoon.

High pressure starts amplifying over the West late in the week. This will potentially send some more triple digit values into the region, primarily in the lower valleys of the desert and the Four Corners. Models also hint at some weak monsoonal flow drifting beneath the high late in the week. These details are just napkin planning at this point, but look like targets of forecast concern in a mostly benign weather week.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 602 AM MDT Sat Aug 15 2026

A few light showers are lingering in northwestern Colorado, bringing lower ceilings and the possibility of light rain showers to KHDN. Showers are unlikely elsewhere this morning. Isolated shower and thunderstorm activity is expected today after 18Z, but the convection is forecast to favor the high terrain. So, TAF site impacts are possible at some mountain sites, but the chances are low. VFR conditions are expected to prevail.

GJT WATCHES/WARNINGS/ADVISORIES

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