A stationary front is a boundary between two different air masses, neither of which is strong enough to replace the other. On a weather map, this is shown by an inter-playing series of blue spikes pointing one direction and red domes pointing the other. They tend to remain essentially in the same area for extended periods of time, and waves sometimes propagate along the frontal boundary. A wide variety of weather can be found along a stationary front, but usually clouds, prolonged precipitation, and storm trains are found there. Stationary fronts will either dissipate after several days or devolve into shear lines, but can change into a cold or warm front if conditions aloft change.
A stationary front becomes a shearline when the density contrast across the frontal boundary vanishes, usually as a result of temperature equalization, while the narrow zone of wind-shift persists for a time. This is most common over the open ocean as the temperature of the ocean surface is usually the same on both sides of the frontal boundary and modifies the air masses on either side of it to correspond to its own temperature.