textproduct: Grand Junction

KEY MESSAGES

- Near-record heat continues Tuesday for western Colorado and eastern Utah.

- Daytime highs for the lower elevations will remain in the triple digits through at least Wednesday.

- Terrain based showers and thunderstorms increase in coverage each afternoon, with a threat for flash flooding becoming more likely by mid-week.

DISCUSSION

Issued at 104 PM MDT Mon Jul 13 2026

The upper high parked across much of the CONUS remains anchored in place this afternoon. Anticyclonic return flow continues to send extratropical moisture northward into the Southwest. This looks like good news for those of us awaiting some moisture to suppress an active wildfire season. Relative humidities have begun to respond with wetting rains last night and RH values we haven't seen in some time. Winds beneath the high remain ambivalent throughout the column on the Grand Junction sounding this morning. Steering flow is pushing terrain based showers and thunderstorms to the west and southwest this afternoon. This will likely spell out more rain for areas southward of the San Juans this afternoon, as those storms drift off their source terrain. Points northward are showing less convection, with only a few lightning strikes thus far.

The high doesn't budge much the next 24 hours and temperatures appear to stall out in the triple digits for our low desert valleys for another day Tuesday. Some relief is in sight though, as West Coast troughing chips away at the height fields Tuesday and Wednesday. This will work in concert with additional moisture and cloud cover to knock afternoon highs back down closer to summertime averages Wednesday and beyond. Coverage of mountain showers and thunderstorms will see an increase too, as the moisture plume beneath the high fills in this week. Critical fire weather finally gets a break, but the threat for flash flooding could quickly replace it. The deeper moisture plume advertised in the model guidance remains well to our west, but multiple days of light rain activity could quickly amplify our risk for longer-lived convection by mid to late week. The light upper level winds will increase residence time for these storms too. This is expected to be an evolving forecast over the next couple of forecast cycles, while we get a better look at local conditions after each round of precipitation.

The upper level pattern remains pretty stagnant over the remainder of the long term forecast. West Coast troughing will make some attempts at flattening the upper level ridge. However, models remain intent on keeping the ridge arced over the Rockies into next week. Extratropical moisture in the Southwest could get a lending hand from a potential tropical depression offshore of southern Mexico. As this feature lifts north and west, our moisture supply might benefit handily from it. It's still premature to get focused on this feature. However, it does look like our hot, dry pattern could be shifting into more of a late summer regime.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 1117 AM MDT Mon Jul 13 2026

Showers and thunderstorms will develop again this afternoon, favoring the San Juans. KTEX and KDRO have the best chances for impacts especially gusty winds up to 40 mph. Other sites could see showers or gusty outflow winds as well, but those chances are low attm. Outside of convection, clouds will also develop over the higher terrain but will not be below ILS breakpoints. A few afternoon gusts of 20 to 25 mph will be possible this afternoon.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Extreme Heat Warning until midnight MDT tonight for COZ001-002- 006-007. UT...Extreme Heat Warning until midnight MDT tonight for UTZ024-027.