What Will the Weather Be

What Will the Weather Be

The sky was gray and cloudy over Washington, D. C. , on the morning of March 9, 1999. The weather forecast called for an inch or two of snow.

But by noon, there was so much snow on the ground that many cars and buses were stuck in it. The airports had to close down. So did the schools. In all, eight inches of snow fell on the city. The weather forecast was wrong. And people were not prepared for the huge storm.

Weather forecasts tell us what kind of weather is coming. But predicting the weather is hard to do. It is easy to see what the weather is like right now. You can go outside and look. Is the air warm or cold? Is it windy or still? Is the sky clear? Or is it covered with dark clouds? Whatever the weather is like, it often stays that way for days at a time.

But then something happens. The wind begins to blow. Air from somewhere else moves in. Sometimes it is cooler air from the north. Sometimes it is warmer air from the south. The new air pushes against the old air. The place where this happens is called a front. Most changes in the weather occur along fronts.

Where cold air pushes against warm air, we say there is a cold front. Cold fronts move fast. They can make the wind howl. They quickly push warm air up and out of the way. The rising air carries water. The water is not a liquid. It is a gas called water vapor. As the air rises, it cools, and the water vapor turns to liquid. High in the sky, the drops of liquid water clump together and make clouds.