As I understand it....firstly yes..strong winds do effect migration. A low/moderate more southerly breeze is the best to bring migrants. An overnite rain is the best for a large fallout,particularily in May when peak migration is taking place. The small birds(song birds et al) migrate at nite,so if it rains overnite,it forces the birds down..thus a fallout. If weather is warm and sunny with a southerly breeze,birds often fly on as far as they can before setting down to eat. Often this will mean by-passing the city. Dont worry..at this point,there are still plenty of birds to come.