
Unforeseeable
Unplanned Events
Use 'unforeseeable' for unexpected events that couldn't be planned for, emphasizing the element of surprise. 
Not Always Negative
'Unforeseeable' doesn't only apply to bad outcomes; positive surprises also qualify. 
Formality Use
'Unforeseeable' is formal and often used in official or business contexts, though it's fine in casual talk too. 