Fertilization of Boulder lawn
I am not sure what kind of grass my lawn contains but I put down a fertilizer plus crabgrass preventer in early April and a weed and feed in late May. This lawn had been neglected for many years. I think a lawn service just put application after application of nitrogen for many years. I think the green look and rapid growth fooled the previous owners into believing they had a great lawn. But my guess is the lawn never grew a good root depth and base. What can I do now to help the lawn develop a better root base other then dig up and start over?
Boulder County Colorado lawns and turf
Here are several Fact Sheets from Colorado State that will give you information on your lawn situation. http://extension.colostate.edu/topic-areas/yard-garden/renovating-the-home-lawn-7-241/ and http://extension.colostate.edu/topic-areas/yard-garden/lawn-care-7-202/
Aerating the lawn twice a year encourages root development and allows oxygen to get to the roots. You can still aerate now, especially with the current rain. Make sure the plugs are 2-3 inches in depth and 3 inches apart. After aerating you can throw grass seed down. Then keep the seed moist and it will sprout, especially the ones that land in the holes.
If you want, the Extension Agent, can do a lawn check for $75. She can give you more in depth information at that time.