First rain in a while around here. I noticed the ash tree in my backyard was oozing bubbles, had never seen that before. It turns out, it's a thing!
It's a really neat occurrence but could be an indicator of other injuries, particularly if you have Eastern Ash Borer in your area. Depending on where the tree is located in relation to structures and your observations of the rest of the tree, it may be worth having an arborist consultation. If you decide to go that route, I'd encourage you to hire a consulting arborist rather than an arborist who will profit from the cut (doubly so if you're fond of it).
Tl;dr super cool, be safe