Forecast update for the week / weekend: storm sytem Wed pm to Sat pm favoring southern CO

09/09/25 8am: Forecast remain on track for the rest of the week with just a few small changes. Scattered storms in most areas today and tomorrow, then better rain chances especially over southwest CO from Thu through Sat as a storm system moves through. The one change I'm seeing is better storm chances in many areas late tomorrow (Wed) but still favoring southern CO.

For the north-central mountains and south-central mountains:

• For today scattered thunderstorms from 2pm-10pm, best coverage will be along/north of a line from Gunnison to Monarch (central mtns will be favored)

• For tomorrow: storms will first develop over southern CO / San Juans after 12pm and then spread north

• For the southern mtn (San Juans to Elks) scattered to numerous storms from 12pm-11pm Wed, turning wet in spots. Rain may continue Wed night into Thu morning

• For the north-central mtns on Wed best chances for scattered storms from 3pm-9pm

• On Thu on/off rain showers for much of the mountains, favoring southern CO / San Juans with rain in the morning. Even for the north-central mtns maybe some rain showers Thu mid-morning, better chances in the afternoon: 12pm-8pm best coverage along/south of I-70

• Friday into Sat will likely be the wettest day with good rain and thunderstorm chances across much of the mountains 12pm-11pm again, favoring southwest CO / San Juans

• Best chances for a little snow in the mountains above 12,500ft will be on Thu night into Fri am and again Fri night into Sat am

• Another chance for rain and thunderstorms on Sat: 11am-11pm

  
  

For Den/Bou and the front-range

• For today isolated to scattered storms from 3pm-10pm, maybe a couple rounds. Best coverage around the edges: foothills, Palmer Divide and east of Denver (eastern plains after 4pm)

• For tomorrow (Wed) pretty sunny and dry initially, then a chance for scattered late day thunderstorms mostly from 4pm-10pm

• On Thu another chance for scattered storms from 12pm-9pm, best chances in the foothills and PD

• Best thunderstorm chances likely on Fri 12pm-8pm but again favoring the foothills

• Another decent chance for scattered storms on Sat: 2pm-9pm but that is more uncertain

  
  

Bottom line: increasing thunderstorm chances this week with best chances for rain (and snow above 12,500ft) from Thu morning through Sat afternoon (with most of the action in the afternoon / evenings)

Looking ahead maybe another, cooler storm system next week around Sep 17th/18th, but it is highly uncertain.

First image shows forecast total liquid precip from now through 6am Sun from latest GFS and I highlighted the area that will have best coverage of rain and thunderstorms (and snow up high) from Wed to Sat. Second image loop shows forecast radar over the next 48hrs (6am this morning through 6am Thu) from latest HRRR. Third image shows the big upper-level trough to the northwest of CO at 6pm Fri via 500mb vorticity and wind (this will be the weather maker for the weekend).