Today's Tuesday Tip comes from the new edition of Thermal Flying by Burkhard Martens

We call it wind shear when the direction and/or speed of the wind suddenly changes at a particular altitude.

The most common wind shear in the mountains is when the valley wind and the met wind higher up are coming from different directions.

The strength and extent of the turbulence caused by such wind shears depend on the velocity. Most of the time it is only noticeable as a light shaking, but in extreme cases, where two strong winds meet, it can be rough.

Wind shears are common in connection with inversions because the wind direction is often different below and above an inversion.

The picture shows a beautiful wind shear situation. The fog is being pushed against the ridge by the valley breeze but the wind is actually coming from the south (arrow). The south side was just soarable up until ridge height where some turbulence announced that I had entered the realm of the valley wind coming from the north.