I have worked search and rescue for the Coast Guard for several years. The phenomenon was similar to a flare being fired. I was traveling north west on I-76 between exit 91 and 75 and viewed the bright green flame travel across the sky toward the mountains from an east to west movement. It was clear across the sky for almost 2 seconds. The fireball was positioned from 30-45° as indicated from the horizon method I have trained mariners reporting rescue flares in the past.
