The FAA defines wind shear as a “change in wind speed and/or direction over a short distance.” The Aviation Weather Center’s Winds/Temps data lists the wind speed and direction at altitudes beginning as low as 3,000 feet (depending on the altitude of the station) and up to 53,000 feet. (You can toggle between an interactive map and a static table.) If there is a large difference in wind speed and/or direction between reported altitudes, that is an indication of wind shear. If there is wind shear, you’re in for a bumpy ride and should consider other route options.
Another preflight resource is the Aviation Weather Center’s graphical turbulence tool. The color-coded map shows turbulence sigmets and graphical turbulence guidance that indicates forecast turbulence. To find these charts, and other weather planning resources, visit the Aviation Weather Center’s website.
Pireps are an excellent source of real-time information directly from other pilots. When factoring pireps into your planning, consider the type of aircraft the report is from (light turbulence in a larger aircraft could be moderate when flying in a single-engine trainer) and timing (the reported weather may no longer be a factor by the time you arrive at that point). While en route, if you encounter turbulence, do other pilots a favor and report it. And, if there was turbulence reported that you did not encounter, that is worth reporting as well.
Visual indications of turbulence while flying include clouds and mountains. For example, air rising below cumulus clouds causes turbulent conditions for aircraft flying underneath. Mountain waves affect flights as far as 100 miles away, and turbulence is worst on the leeward side of the mountain.
A combination of information from weather reports before and during the flight, and visual cues while aloft, will help you plan the altitudes and route that will reduce the amount of turbulence you encounter.