Yes, pursue it. Knock on delays must be excluded from the extraordinary circumstances defence. Weather is part of the normal day to day running of an airline. Obviously bad weather directly stopping a specific flight from operating is excused but not any and all weather events an aircraft previously experienced. The airline must and does plan standby aircraft and crew for this, especially at one of their bases. Oh, and the inbound having insufficient fuel to reach its destination may point to a severe safety issue, since there are strict rules on having additional fuel on board. They must carry enough to reach a nominated alternative airport after reaching the original destination as well as (I believe) an additional hour of flying.