How does Ralston survive a night outside in a whiteout storm?

When Ralston gets stuck and lost in a whiteout storm, he finds snow compact enough to dig a snow cave. He stays put for five hours, peaking every once in awhile to see how the storm is doing. Once the storm clears enough to see some peaks, he uses his maps to identify where he is currently at. Once his location is found, he is able to find his way back home.