prow.istio.io will update from a November 2018 to June 2019 commit tomorrow (Tue July 2, PST), as well as switch to using upstream images.
The goal is for this to be a transparent experience for contributors, but it is possible we get something wrong. In that case it may result in a brief prow outage while we fix things.
Please see #oncall or https://github.com/istio/test-infra/issues/1396 for current status and/or feedback.
Thanks!