As far as I can tell Winklebleck was given 100 months in 1999. He looks to have served the entire time as it looks like he got out in early 2007. I see no probation violation until the incident of kidnapping and assault. Presumably, he was complying with the probation requirements until that evening. There's a couple of kids who I've found with names that must be connected with him in the Portland area--same middle and last name. There's also a woman with the same last name who might be a former wife or sister.
I don't know where he'd be going inland as I don't see any past record of him living there or family. BTW, he's 42. If they catch him, he'll have lots of charges slapped on him. The girls weren't minors, however, they are reported to be in their "early twenties".
Clarkston, WA is about 350 miles from Portland and there's only one road. windy and narrow 84 which follows the Columbia River. It shocks me that they haven't seen him if he's still in his original truck. I haven't read of them finding the truck ditched. My guess is that he's heading into far Eastern Washington or Idaho to hole up.