Weather front facts
A weather front is a boundary in between two masses of air of different densities, and is the main cause of significant weather. In surface weather analyses, fronts are depicted using various colored lines and symbols. The air masses separated by a front usually differ in temperature and humidity.
Cold fronts may feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. Warm fronts are usually preceded by stratiform precipitation and fog. The weather usually quickly clears after a front passes. Some fronts produce no precipitation and little cloudiness, although there is usually a wind shift.
Different air masses which affect North America, as well as other continents, tend to be separated by frontal boundaries. In this illustration, the Arctic front separates Arctic from Polar air masses, while the Polar front separates Polar air from warm air masses. (cA is continental arctic; cP is continental polar; mP is maritime polar; cT is continental tropic; and mT is maritime tropic.)
Weather front Facts for Kids. Kiddle Encyclopedia.