I found a list compiled from Ohio State University saying a list of fruit trees that can be grown near Black Walnut trees. (Surprised me I thought no fruit baring trees went near walnut trees) Cherry was on the list of things you can plant near a walnut tree. I am considering 50 foot from trunk...not the drip line for the planting.

After researching I don't feel I should have any trouble at all...surly weeping cherry falls into the same category as a cherry fruit baring tree in being tolerant of juglone. Even though it is considered an ornamental tree.

http://www.planterspalette.com/wp-content/uploads/2009/04/black-walnut-toxicity.pdf