Weather Tidbits: Overrunning Precipitation

This edition of Weather Tidbits will be discussing overrunning precipitation. Overrunning precipitation occurs when advancing warm air hits colder air already in place at the surface. The warmer air is forced upwards and overruns the denser, colder air. The warm air cools as it rises, causing the moisture in the air to condense into clouds and precipitation. Eventually, the warmer air cools down enough to a point where clouds and precipitation can’t form. If the cold air at the surface is below freezing, there would be sleet of freezing rain. But if the colder air is above freezing, the precipitation will generally be all rain. Either way, both situations are still examples of overrunning precipitation. These set-ups are very common with warm frontal passages.