In any case the winds are cutting or shearing across each other. Turbulence is caused when an airplane passes through a region of wind shear or when a plane passes in and out of a jetstream. It is also common near mountain ranges. Since air is invisible, turbulence is sometimes not known until a plane experiences it. An air pocket is when the plane hits a region of sinking air that causes a rapid loss in altitude.
Severe weather is sudden, violent, hazardous weather that comes from powerful thunderstorms.
It could be large hail, flash flooding, extreme winds or tornadoes. Severe storms are most likely in the late afternoon but they can happen at any time, day or night. Keep up with the weather forecast and get a NOAA Weather Radio. They are inexpensive and sold at most electronics stores. A watch means severe weather is possible.