I live in Central Virginia and we got hit hard - still have a couple thousand who have not gotten their power back. We were out only 2 days. Here's bit of info from the extension office...hope it helps a little. I need to go check out my black walnut tree, too, to see if many got knocked off by Irene.
Allow nuts to ripen on the tree. After harvest, you must husk and cure the nuts for the best flavor. Remove the outer skin of the walnut, the husk, and dry the nuts to cure them. After curing, nuts can be used or stored either shelled or unshelled. Two pounds of unshelled black walnuts found in the wild will yield about a cupful of nut meats.
Harvest
As black walnuts ripen, the husk changes from solid green to yellowish green. Walnut juice leaves a dark stain, so wear gloves or use tongs when you handle unhusked walnuts. Press on the skin of the walnut with your thumb; ripe nuts will show an indentation. Weekly monitoring is important as nuts will mature over a four to six week period. Try to harvest the ripe nuts directly from the tree, ahead of the squirrels. If the nuts are too difficult to reach, they can be collected after they fall from the tree during frosts. Often the husk of mature nuts has dried and cracked. Husks must be removed before you store black walnuts.