Why do you think a cold front is considered more active than a warm front?
By simply looking at the characteristics of cold and warm fronts, you will see why cold fronts bring more “active” weather. In a cold front, cool air is shoved underneath the warmer air already in place. The warm air is lifted very abruptly and as it cools, the moisture associated with the warm air will condense and form clouds. Due to the rather sharp slope of the cold front, it is able to lift the warm air abruptly enough to produce thunderstorms given that other ingredients such as instability and moisture are in place. In warm fronts, the slope is far less steeper thus there isn’t a great source of lift for thunderstorm development as you’d see with cold fronts. Warm fronts are more known for bringing a relatively large area of precipitation of moderate intensity while cold fronts are known for producing bands of thunderstorms, some fairly intense.
