What phenomenon is commonly associated with wind shear during flights?

Wind shear is a significant change in wind speed or direction over a short distance. It can occur at any altitude but is particularly critical during takeoff and landing phases of flight. Passing frontal systems are associated with wind shear because they represent a boundary between two different air masses, often leading to abrupt changes in wind direction and speed. These systems can create turbulence and variations in aerodynamics, potentially impacting an aircraft's performance and stability.

In contrast, the other options do not effectively relate to the phenomenon of wind shear. Flying over water is not directly connected to wind shear, as water bodies do not inherently cause changes in wind profiles. Stable atmospheric conditions typically indicate a lack of turbulence, which is opposite to what is experienced with wind shear. Low humidity levels do not directly correlate with wind shear occurrences either, as wind shear pertains more to the dynamics of air movement rather than moisture content in the atmosphere. Understanding these dynamics is crucial for anticipating and managing the effects of wind shear during flight operations.