Vagrant has a lot of output on the command line, which will quickly scroll off the end of the console. To my knowledge Vagrant does not write this output to a log file. So use PowerShell's Tee-Output to both capture it in a logfile, and send it to the console. Handy for troubleshooting after those hour long runs starting a fresh web8-allinone box. I also looked into Start-Transcript, for a log dile Tee-Object works better for me.
vagrant up --provider=virtualbox | Tee-Object web8-box.log