Modifiers matching circumstance:

• unfortunate,
• common,
• unusual,
• unforeseen,
• external,
• exceptional,
• unforeseeable,
• stressful,
• threatening,
• personal,
• unexpected,
• unique,
• negative,
• verifiable,
• extraordinary,
• individual,
• special,
• relevant,
• catastrophic,
• severe,
• extreme,
• historical,
• bad,
• involuntary,
• exigent,
• unavoidable,

Simple categories matching unforeseeable:

• development,
• event,
• calamity,
• setback,
• situation,
• occurrence,
• incident,
• circumstances,
• inactivity,
• reason,
• change,
• risk,
• cause,
• disturbance,
• circumstance,
• disaster,
• contingency,
• catastrophe,
• thing,
• condition,