As Seattle Transit Blog reminds you, there’s a significant bicycle event happening this weekend, and if you’re not in it, you probably don’t want to stumble upon it on the way to pick up milk for your cereal:

Saturday is also the 32nd annual Seattle to Portland Bicycle Classic (STP). 10,000 cyclists (including yours truly) will make the 204-mile trek to Portland. For our mutual sanity and safety, you would do well early Saturday morning to avoid Montlake, the University Bridge, Lake Washington from Madrona to Renton, West Valley Highway, Puyallup, Pacific Avenue/SR7, and SR 507. [emphasis added]

The scene for the ride’s start is the University of Washington E-1 parking lot, on Montlake Blvd., just north of Husky Stadium. One-day riders depart from 4:45 a.m. to 5:15 a.m., and everyone else from 5:15 a.m. to 7:30 a.m., in 10-minute waves.

This is the sixth year for one of the more unlikely STP teams, the 25-member Cruiser Bike Team for Prader-Willi, sponsored by Snohomish’s meal assembly chain Dream Dinners.

The ride itself is sponsored by Group Health, so it’s not that unusual that the cyclists in Hawaiian shirts and flip-flops are raising funds for and awareness about Prader-Willi syndrome (it’s genetic, and kids who have it feel chronically hungry, along with suffering from learning issues).

It’s not a joke; they’re on 42-pound fat-tire cruisers for 204 miles and 22 hours, and team captain Mike Kuna says the experience is “like nothing else.” He did the first ride in 2006, with just one cyclist companion, and the team has been growing swiftly since–people who do it once, against all odds, come back the next year for more. Now they have cyclists from Washington, Oregon, California, Colorado, Ohio and Arizona.

Dream Dinners, besides supporting the team with bikes, logistics, and food, also runs Living the Dream Foundation, for online donations. Over the last six years, Dream Dinners and the cruisers have raised more than $50,000 for Prader-Willi research and treatment.