You might run into snow by Beehive Meadow. Snow for sure by the time you get to the Moraine Ridge trail junction. The snow will be pretty dense so you can probably walk over it without too much trouble especially in the morning. The last mile or so along Falls Creek is open granite and a southern exposure so it may be clear of snow.
Since the trail may be obscured by snow be sure to have a good topo map or a GPS with the Yosemite topo in it.
5/4/2008
A friend just got back from a trip to the top of Wapama Fall and you can see in photo 3131 that there isn't much snow in the Falls Creek watershed below Vernon.
http://yosemitephotos.net/main.php?g2_itemId=2971Post Edited (05-04-08 21:16)
Old Dude