A "wave of clouds" seems to break against the base of Big Mountain at Whitefish Mountain. And below lies some wonderful skiing, both on groomed trails and through the trees. The low clouds are called an inversion. When the inversion develops, it can often hang around in this part of Montana for more than a week. Down in the valley it is cloudy, gray, cold and sometimes just plain miserable. Meanwhile, up in the mountains, the sun shines constantly and the temperature is often 10-15 degrees warmer than down in the valley. When inversions strike this part of Montana it is truly a wonderful excuse to go skiing.