If they open it on schedule at 9 AM on May 21, it looks like I'll win the dcTPP (Darn Close -- Tioga Pass Prognosticator) as I'm less than 24 hours off.
My phone predicts snow in Mammoth on Monday so it sounds like I have to hope for enough of it to prevent them from opening Tioga, but not enough to keep it closed for more than a day.
I found this website when Googling to find out when Tioga may open as I was planning a trip to Mammoth before Memorial Day and the last few times I've done it in May, I've had to return via Sonora Pass or Monitor and Carson Passes. I've moved back my planned trip by a day this year since making my prediction. I now want to return on Tues. although could delay until Wed.