You should be okay. The snow is mirroring where we were on the melt-out last year at this time, plus we've had 3 distinct peaks, so flows should be in recession. Yes, the rain is a wildcard, but unless a big rain within a couple days of your trip, the amounts being forecast will do little than slow the recession or give a quick spike. I'm predicting 8000 to 10000 on my May 31, or about 3.5 to 4. And personally, I think anything in the 4.5 to 5.5 range is a similar experience and requires the same skills and decision making (although 5.5 is definitely pushier than 4.5).
here is a plot of flow this year vs. last: