Jeff Pickard, age 10, of Grand Forks, N.D., for his question:

JUST WHAT IS A CHINOOK WIND?

Chinook is a name given in the northwestern United States and western Canada to a strong, warm and dry south or west wind that comes from the Rocky Mountains.

As warm, moist air blowing off the Pacific Ocean travels over

the Rockies, much of the moisture condenses out on the western slopes. This process warms the wind, which undergoes further heating and drying as it descends the eastern slopes.

In early spring the winds often melt the snow very quickly, but their effects are observable only in valleys, where the temperature increases due to compression is at its greatest.

The name of the wind is derived from the Chinook Indians in whose territory the phenomenon was first observed.

Similar winds can be found in the European Alps. There they are called foehns.