The tarp is out because it's been raining on and off in Detroit all day. Nothing hard, but a steady drizzle. I guess that's the best way to describe it.
CBS Detroit says the weather situation will remain the same all day and into the night. At this very moment, it's a playable rain. This wouldn't cause a delay or a postponement during the regular season, but who knows about MLB will approach things in the postseason. There might be a problem if the rain picks up. That isn't expected to happen right now and hopefully it doesn't.
Either way, Game 5 will be played in something less than ideal conditions.