If you're using popover, also use the dialog element for your modal dialogs

Popovers are displayed in the browser's top layer, a layer that is a bit like a sibling to your html element. It means they are always above non-top layer elements. The only other elements that can be in the top layer are dialog elements shown with showModal(). If your app also has modal dialogs, make sure they are shown with the showModal method of the dialog element, so that they can appear on top of your popovers. This becomes especially clear when the modal dialog exists for things like session time out warnings, as I show in this video.