This year, the autumnal equinox falls on Saturday, Sept. 23, ringing in the arrival of the next season. But, here in our higher-elevation mountain towns, the trees have already announced fall’s arrival as pops of red and orange decorate the hillsides. To the trained eye, this seasonal arrival is actually later than usual. “The colors are coming in a little behind, slightly slower than average, and there’s still a lot of green,” says Johnny Adol…