Mystery Underwing Moth

On the night of September 14, 2014, we surprising large numbers of a very large moth fluttering about the porch light here at Moorecroft Regional park, in Nanoose Bay, BC. Watching them for a few moments, I felt that it was a species that I couldn't recall having seen before. Later in the evening, I realized that several must have come in when I had the door open, and were now noisily bumping into lamp shades around the house. As large as they were, it didn't take long to capture them and release them outside. Curious as to the species, I photographed one, thinking I could identify it later. Well, I should have known better. After sending the photos to quite a few different people, there was no consensus as to what the species was, although Catocala semirelicta and Catocala unijuga were the most commonly suggested species. Reading about the abundance,  distribution and habitat preferences of the two moth species, it seems that semirelicta is more likely. Next time, I'll make sure and wait to release the moth AFTER it has been identified.