A vertically collapsible weather resistant barrier for an opening, having a plurality of side frames secured along the height of side walls and/or an intermediate post defining the opening. Each side frame has a longitudinal channel along its length facing inward toward the opening. The channel accommodates sheaves extending from the barrier and by which a ceiling mounted pulley system may house and lower the barrier with the side frame. The barrier comprises a plurality of pantograph structures at opposite ends of a plurality of panels. The arms of the pantograph structure closest to the side walls house a locking mechanism thereon facing the side frame at either end of the arm that engages a latch in and a proximate arm to pull them into tight vertical alignment when substantially fully extended. The locking mechanisms are covered by an expandable bulb seal that bulges outwardly when the locking mechanism is engaged to create a seal between the pantograph and the channel in the side wall