CURRENT SURFACE WEATHER MAP ACTIVITY
(Hardcopy Version)

Note: Before completing this activity, print a hardcopy of this document.

PURPOSE/OBJECTIVES

Surface weather maps depict large-scale weather systems called Highs, Lows, and fronts. In this activity, you will learn how to interpret surface weather maps. After completing this activity, you should be able to:

describe the current weather conditions at different locations around the United States;
relate the weather conditions where you live to weather systems shown on a current surface weather map;
predict the weather changes that are likely to occur as weather systems approach and pass different locations on the weather map, including your location.

BACKGROUND

If you know how to interpret a weather map, you will know a lot about what the weather is like now and what the weather is likely to be in the future.

How Weather Maps are Made

The National Weather Service (NWS) maintains dozens of observing stations throughout the United States. At these stations, meteorologists report hourly observations of atmospheric conditions including air temperature, dew point temperature, air pressure, wind direction and speed, cloud cover, and current weather (e.g., rain, snow, fog, etc.).

These data are plotted on maps of the United States. On the map, each NWS Office appears as a small circle; weather observations are systematically arranged around the circle in what is known as the station model format. Meteorologists carefully analyze the weather map to determine the location of large-scale weather systems such as Highs, Lows, and fronts. Simplified versions of these maps appear in newspapers and on television.

Interpreting Surface Weather Maps

Air Masses/Highs: An air mass is a large body of air with fairly uniform temperature and humidity conditions. Typically, air masses have high surface air pressure in their centers--air masses are called "Highs." Within the center of the air mass, the point on the map with the highest air pressure is marked with a large "H." Highs are usually associated with fair weather and clear skies. Winds blow clockwise around highs.

Lows: Low pressure centers, called "Lows," form along the boundary between different air masses. Lows appear on the weather map as large "L's." Lows are usually associated with cloudiness and precipitation. Winds blow counterclockwise around Lows.

Highs and Lows influence the weather across broad geographic regions.

Fronts: Warm and cold air masses do not readily mix; the boundary between different air masses is called a front.

When a warm air mass displaces a cold air mass, the boundary is called a warm front. The advancing warm air is less dense than the retreating cold air, so the warm air aloft overruns the cold air near the earth's surface, resulting in a widespread layer of clouds ahead of the weather map warm front. Steady precipitation usually falls before a warm front arrives. After the warm front passes, the air temperature rises.

When a cold air mass displaces a warm air mass, the boundary is called a cold front. The advancing cold air is more dense than the retreating warm air, so the cold air forces its way under the warm air, resulting in brief, showery precipitation. After the cold front passes, the air temperature falls.

Sometimes the boundary between different air masses isn't moving; this is called a stationary front.

Additional Information

For additional information about weather systems, follow the hypertext links to the following Web sites:

MATERIALS

To complete this activity, you will need the following:

Microcomputer with Internet access (direct or dial-up connection) to the World Wide Web;
Web browser capable of displaying GIF files, such as Netscape or Microsoft Internet Explorer;
Color printer (optional).

PROCEDURE

Download/print a hardcopy of this activity
Access a current surface weather map.
Display (on-screen) and/or print hardcopy of a current surface weather map.
Answer activity questions.

ACTIVITY QUESTIONS

How many high pressure systems (Highs) are shown on the weather map? Where are their centers located? In your answer, use either state names or geographic regions of the country (e.g., Mid-Atlantic states) to describe the location of the Highs.
How many low pressure systems (Lows) are described on the weather map? Where are their centers located?
What kinds of fronts are shown on the weather map? Where are they located?
Where is the weather likely to be fair (clear and dry)?
Where is it likely to be stormy (cloudy, with a chance of precipitation)?
According to the weather map, what is the weather likely to be in your area? Is it?
Based upon the current surface weather map, forecast (predict) tomorrow's weather for your location.

Please send your ideas and input to:
Walter Sanford, Director
Hypermedia Geoscience Curriculum Project
Internet: wsanford@pen.k12.va.us

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CURRENT SURFACE WEATHER MAP ACTIVITY (Hardcopy Version)