I just looked at the Jasper forecast at the Environment Canada website, which shows up to Aug. 7th: weather.gc.ca/forecast/city_e.html… It's basically showing seasonally average values for the entire time span. Note that the days with the rain icon show a "60% chance of showers" - that likely means a sunny morning, increasing cloudiness through the day, and a shower in late afternoon or evening... a pretty common weather pattern here.
Banff is looking pretty similar.
The weather forecasts are often not terribly accurate in regards to specifics, although they usually get the trend right... although they are often "off" by a day or two. There was a thread about mountain weather here on one of the TA forums within the last few days, with someone worried about a similar forecast - 60% chance of showers... it never rained at all that day.
I'm not sure what you were expecting, but this is pretty typical weather for summer in the Canadian Rockies.