Usually during the day when UV creates ionized clouds in the E layer, sporadic E skip. It can still happen in the evening when there are strong "left-overs". Top frequencies? Check out the FM broadcast thread for what was heard in Canada.
NENJ isn't out of the coastal ducting area, tropo we're famous for so keep your ears on 156.800MHz, marine channel 16 "beacons" will tell you when it's happening. When you hear the Coast Guard coming from Woods Hole and Hatteras VHF is open.