The American NOAA publish so called significant weather charts (SIGWX) on their
website. These are used for actual flight planning.
Areas where clear air turbulence must be expected (CAT AREAS) are marked with dashed lines and the relevant altitudes are given in the legend. The figures state the lower and upper limits in hundreds of feet and the symbols denote the expected intensity. One chevron on a line stands for moderate turbulence and a double chevron on a line for severe turbulence.