hi,
we just got back from our trip to yosemite. we were there last monday when they closed the valley. basically the rangers closed off traffic heading to the valley so we turned around and headed to mariposa grove (we stayed at yosemite west). from what i understand, the rangers turned people away from the entrances to the valley at SR 120 & 140. people who camped at lower ground had to be evacuated.
the waterfalls were spectacular as a result. i would call the park hotline at 209/372-0200 for road closings if flooding is an issue.
i also recommend bringing a poncho and bug spray! the mosquitoes are already really bad!!
tina