This may be due to sun scald because the area affected is exposed to sun and wind.  Check though to see if any insects are present that may have caused this.   Increase deep watering; it's more effective than frequent shallow watering, and mulch around the tree.  Prune any dead branches and apply a high-nitrogen fertilizer in the spring.  To learn more about sun scald, see
https://extension.umn.edu/yard-and-garden-news/sunscald-and-winter-dieback-shrubs

Good luck with your tree.