Billy Richards age 11, of Boulder, Colo. for his question:

What causes the chinook wind?

Once in a while, a chinook wind creates enough fuss to get into the news. This happened on January 13$ in 1913. At eight in the morning the temperature at Rapid City, South Dakota was 49 degrees below freezing; Brrr The rolling black hills were deep under white snow, This midwinter weather was not suprising and everyone expected it to continue. But by ten o'clock that same evening the thermometer had zoomed up to a balmy 4'7 degrees .6 a leap of 96 degrees Fahrenheit] At 15 degrees above freezing, tons of firm snow melted into gushing riverlets. What caused the deluge? A warm$ dry gusty chinook wind had come rolling down the eastern side of‑the Rockies,

A few days before it had been an ordinary westerly wind traveling over the wide Pacific. It was a winter wind, cool from brushing with the winter winds coming down from the polar regions, How did it manage to warm itself up in the middle of winter? It suddenly bumped into the talk massive Rockies. It warmed up during the process of getting over the top. For a wind has as much trouble getting over a mountain as you do, It must go through a series of changes during which it loses much of its moisture and gains in temperature,

Trouble started when this cool, gentle westerly began to pile up on the western side of the bulky Rockies. Crowded winds are, it seems, uncomfortable:, and try to break the tension by expanding and spreading out in all directions. But this westerly wind was pretty well boxed in. There was a wall of mountain ahead and a crushing current of air behind, It could only expand upwards.

This was fine. For it heaved the blowing air in its first lap over the mountains, But once aloft, the air became spread out thinner and lighter. This caused it to cool. And cooling air tends to lose its moisture. As the temperature fell, surplus vapor was squeezed out of the air and dropped. What day, the tall Rockies received an extra crown of snow.

The wind aloft was now very cool, light and dry. It was ready for the long slide down the eastern slope of the mountains. In this merry jostle, the air piled up and became or bwded again.  It lost temperature as it expanded and became  expanded and became thin. Now it gained temperature as it piled up and became heavier. By the time it reached the ground level it was a warm, dry, gusty wind, The chinook wind blew over the northern prairies, whipping off branches and melting the deep snow as it went.

The chinook is a local wind and occurs where prevailing winds have to get themselves over bulky mountains. Such a wind blows down the northern slopes of the European Alps. There it is called the foehn winds pronounced to rime with the word burn. The chinook, of the northwest regions of our continent is named from a tribe of Indians. The camp of the Chinook Indians was in the path of the chinook wind.