5) Frontal Turbulence Frontal turbulence is caused by lifting of warm air, a frontal surface leading to instability, or the abrupt wind shift between the warm and cold air masses. The most severe cases of frontal turbulence are generally associated with fast-moving cold fronts.
Mechanical: This is caused by interference of surface features on the horizontal flow of air. This could include mountains, Tall buildings, Trees, etc. The amount of turbulence depends on speed of wind, the size of the obstruction, the shape of obstruction and atmospheric conditions.
the presence of mountain wave turbulence within 50 miles or so, you should use satellite imagery as a pre-flight tool to identify mountain wave turbulence over an extended route of flight. Lines of ASCL associated with mountain wave turbulence look like ripples in a puddle of water in satellite imagery. (Figures 7 and 8).