My weeping cherries have bark wounds. What caused this?

This is likely sunscald. Sunscald happen in the winter when the bark freezes at night and then thaws during the day. UT Extension Agent Joseph Seago talks about why it happens and how to protect your tree.

Related Videos:
Effects of Sunscald
How do you prevent sunscald on young fruit trees?

Related Resources:
Environmental Injury: Sunscald and Sunburn on Trees​
Sunscald Injury or Southwest Winter Injury on Deciduous Trees