Next storm system will impact northern CO Tue pm through Wed pm

09/15/25 8:15am: Morning, its Monday and we have some weather to talk about. Models show an upper-level low moving across northern CO Tue night into Wed morning, this will pull some colder air and moisture into northern CO and provide better storm chances for the front-range and north-central mountains tomorrow afternoon into Wed am.

I circled the area on the first image below that will have the biggest impacts, including some snow above 11k ft tomorrow night (especially over the northern front-range mountains).

For Den/Bou, the front-range and northeast plains:

• For today warm and breezy (high in the low 80s), just a few very isolated high-based storms after 4pm, most areas stay dry

• Cold-front moves down the front-range tomorrow morning

• Then a good chance for scattered thunderstorms and some rain from 3pm-11pm (best chances 5pm-8pm). Best coverage from Denver north to Ft. Collins and east

• Strong thunderstorms expected over northeast CO (east of Akron) from 4pm Tue through 2am Wed

• Coldest air aloft moves in late Tue night into Wed am, it will likely be cloudy and cool along the front-range on Wed, high only in the 60s

• On Wed another chance for isolated to scattered storms, favoring the front-range mountains and foothills after 12pm

• Cool air will remain in place on the front-range through Thu (high temps in the 60s / low 70s)

  
  

For north-central mountains including Routt, Eagle, Summit, Grand, ClearCreek, western Boulder/Larimer counties

• For today after a chilly start, seasonable warm and sunny and breezy at times. Windiest conditions over northwest CO and near the WY border

• Initial cold-front also works its way into the northern mountains by tomorrow mid-day, turning much cooler by Tue evening into Wed

• On Tue: isolated to scattered thunderstorms and some rain expected from 2pm-11pm, with best chances 6pm-10pm, best coverage from Vail east and along/north of I-70

• Rain/snow on Tue night will favor the northern Front Range mountains and foothills (RMNP to Cameron Pass areas).

• Some snow for the Front Range mountains (and maybe eastern Summit Co mountains) above 11k ft on Tue night into Wed

• Coldest air moves into the mountains by early Wed am... Wed will be chilly in the northern-mountains with high temps only in the 40s/50s

• A few isolated storms on Wed after 12pm, again favoring the northern front-range mountains

• Little impact south of Summit Co from this storm system

  
  

Looking ahead, the weather dries out and warms up starting Thu for the mountains and Fri for the front-range. This upcoming weekend looks dry and much warmer (low 80s for Den/Bou and 60s for the mountains this weekend, should be great).

First image shows forecast total liquid precip from now through 6am Thu from latest NWS Blend of models, take amounts with big grain of salt but I circled the areas that will have the biggest impacts. Second image shows the weak upper-level low at 9pm Tue via 500mb vorticity / wind from latest ECMWF. Third image shows the much cooler air aloft being pushed into CO from the north on Wed am, via 700mb temps/wind from ECMWF. Fourth image loop shows forecast radar over the next 48hrs (6am this morning through 6am Wed) from latest HRRR, take with a grain of salt but gives generally idea of thunderstorm / rain timing.