Stationary Fronts

A stationary front is a boundary between two air masses that are not moving. The weather along the front will vary from clear to showery, depending on the air masses involved.

Why do fronts stop moving in the first place? It depends almost completely on upper level winds. Fronts move when upper level winds are perpendicular to the front. When these winds change direction and blow parallel to the front, the front "stalls" and becomes stationary. Many times the front will dissipate over the stall region. If the upper winds change direction again, then they will start moving again.

From a weather perspective, stationary fronts are a good place for new low pressure systems to begin. Low pressure systems often result in storms. By themselves, stationary fronts are characterized by gray skies, often with rain or snow. Precipitation is a result of warm air overriding the cooler air typical of stationary fronts.