The conditions as of Monday night were very good. 99% of the trails were dry as a bone with a few minor (typically) wet spots. Any soft conditions due to yesterday's rain will be gone by the end of today. I'm not sure how much rain is forecasted for Friday. If only a little, you should be good to go. If an all day soaker, I would skip Stephens and head to Allamuchy North. That place drains VERY well.
Similar to Allamuchy North, the northern parts of Stephens drain rather well....it's just the lower trails (Red along the river, Pink Maze, Holy Grail trail).