Forecast for this upcoming week, tracking a storm system for Thu-Sat (09/11-09/13)

09/07/25 9:20am: Morning, happy Sunday. We have a little short-wave moving across northern CO at the moment producing some rain showers over parts of the Front Range mountains with extensive cloud-cover over the front-range urban corridor (Den/Bou). This wave will keep things a bit unsettled today before we warm up and dry out for several days, a return to summer wx at least through Wed / Thu.

At least this short-wave will push most of the thicker smoke out of the state today, so much improved smoke conditions along the front-range (but still some).

Then I'm tracking an upper-level low over the western U.S. that will likely bring some more unsettled weather to CO from Thu through Sat but there is uncertainty about the impacts. But generally much better rain chances especially for the mountains on Thu and Fri this week (with some snow above 12,500ft).

For Den/Bou and the front-range today, cloudy this morning, turning partly cloudy and warm through mid-day, then a chance for isolated to scattered thunderstorms from 1pm-6pm (best chances 2pm-5pm), best coverage along/north of I-70 and along/east of I-25.

For the north-central mountains today: cloudy with a few showers east of the Cont. Divide this morning, then some isolated thunderstorms from 2pm-10pm, best chances this afternoon after 3pm, best coverage along/north of I-70 and along/east of the Cont. Divide (front-range mountains will be favored), won't be much.

Looking ahead, warm and mostly dry across the state on Mon, just a few high-based, isolated storms for the mountains 2pm-8pm.

Moisture starts to increase some (from the southwest) on Tue into Wed so increasing thunderstorm coverage across the mountains on Tue and Wed (but still isolated to scattered storms): 1pm-8pm each day, hit or miss nothing too major.

Then as the upper-level low approaches from the west, deeper moisture will be pulled into the state from the southwest. Its unclear exactly how this upper-level low will evolve....will the main low stay well west of CO, or will the low move over northern CO on Fri into Sat as the latest GFS is showing with better rain and snow chances (snow above 12ft primarily).

Biggest impacts from the low will likely be from 12pm Thu through 12pm Sat (09/11-09/13). Initially better afternoon thunderstorm chances over most of the central mountains (north and south central) on both Thu afternoon and Fri afternoon: 12pm-9pm each day. Heavier rain and thunderstorm coverage likely over southern CO but all of the mountains should get in on the action. There could be rain/snow in the mountains Fri night into Sat morning.

For Den/Bou and the front-range, also much better thunderstorm chances on Thu and Fri afternoon (mostly after 1pm each day). Then maybe turning a bit cooler, cloudier on Fri into Sat morning as the main low passes through.

That is all for now. Get ready for the first snowfall contest which I'll be posting about tonight (first snowfall at anyone's house, first snowfall in Dillon/Silverthorne, first snowfall for Denver/Boulder), I'll have much more on that later.

First image loop shows current, local satellite/radar/surface overlays showing this short-wave and rain showers. Second image shows forecast radar at 4pm today from latest HRRR. Third image shows the upper-level low at 6pm Thu via 500mb vorticity / wind from latest GFS (the track of the low is uncertain).