PURPOSE:  To describe the atmospheric conditions that result in snowfall.

MATERIALS: Thermometer or thermograph, hygrometer or psychrometer, aneroid barometer or barograph, anemometer, wind vane, meter stick, weather data sheet(s).

INTRODUCTION:  Meteorology is the study of the changing condition of the atmosphere.  Although the weather is not always predictable, knowledge of atmospheric conditions increases the chances of correctly forecasting the weather.  Snow is a major component of winter weather.  It affects the distribution and survival of plants, animals and humans -- and sometimes a large snowfall even causes schools to close!

In this activity, you will collect data on winter weather conditions over several weeks.  If there are some snowy days and some days without snow, and maybe even a large snowfall, the meteorological information you gather will help answer the question, "When does it snow?"

PREDICTION: Use your own experience, and what you've learned from your textbook and TV weather forecasts, to make some predictions.

1.  What weather conditions (temperature range, wind direction and air pressure change) are associated with snowstorms in your region?

PROCEDURE: Each day for at least two weeks, record weather information on the data sheet(s).  Some data may be obtained by direct observation or from the weather instruments set up in school.  Newspaper, radio or television weather reports should supply the rest.  Use a conversion chart to change English units to metric units.

CONCLUSIONS:

2. Identify the weather instrument that is used to measure each of the following atmospheric conditions:  temperature, relative humidity, air pressure, and wind speed.

3. Is there a relationship between temperature and amount of snowfall?  Give some examples from your data.

4. How does the relative humidity on snowy days compare to that on days with little or no snow?

5. Is there a relationship between temperature and relative humidity?  What usually happens to relative humidity when there is a drop in temperature?

6. What type of pressure system is associated with snowfall?

7. Is there a relationship between wind speed and amount of snowfall?  Give some examples from your data.

8. From what direction did the winds usually blow on snowy days?  Was the wind direction different on days without snow?

9. What type of clouds are "snow clouds"?

10. Based upon your data, what atmospheric conditions are most favorable for heavy snowfall?

DISCUSSION:

11.On extremely cold winter days some people say that "it is too cold to snow".  Do you agree or disagree with this statement?  Explain your reasoning.

12.Despite the satellites and computers available to meteorologists, sometimes winter storms come as a surprise.  Why are weather forecasts not always correct?

Figure 1. Sample Filled-in Chart Sections