>>20586449You should be able to snatch it, Gale Wings only gives a +1 priority to all Flying Type moves.
Snatch has a priority of +4 in relation.
It's already able to snatch even without taking this into account, but since Tailwind is neutral before hand, you shouldn't have a problem.
So long as you snatch prior to the opponent using it.
If it's already active, you cannot snatch it.