Thunderstorms and related phenomenon. Turbulence of moderate degree or greater. Icing of light degree or greater. Volcanic ash clouds are reported or forecast. Moderate Unsecured objects are dislodged.
Occupants feel definite strains against seat belts and shoulder straps.
Severe Occupants thrown violently against seat belts. Momentary loss of aircraft control. Unsecured objects tossed about. Extreme Aircraft is tossed violently about, impossible to control. May cause structural damage.