Wave Soaring in Oregon

Via Gary at NW Skysports, taken from his glider on Saturday. The clouds are called lenticular clouds, described well here (scroll down):

The great attraction of soaring in mountain waves stems from the continuos [sic] lift to great heights. Soaring flights to above 35,000 feet have frequently been made in mountain waves. While mountain wave soaring is related to ridge or hill soaring, the lift in a mountain wave is on a larger scale and is less transitory than lift over smaller rises in terrain.

When strong winds blow across a mountain range, large "standing " waves occur downwind from the mountains and upward to the tropopause. The waves may develop singly; but move often, they occur as a series of waves downstream from the mountains. While the waves remain about stationary, strong winds are blowing through them. You can compare a mountain wave to a series of waves formed downstream from a submerged rocky ridge in a fast flowing river. ...

If the air has sufficient moisture, lenticular (lens shaped) clouds mark the wave crests. Cooling of air ascending toward the wave crest saturates the air forming clouds. Warming of air descending beyond the wave crest evaporates the cloud. Thus, because of continuous condensation windward of the wave crest and evaporation leeward, the cloud appears stationary although wind may be blowing through the wave at 50 knots or more.

The above picture is taken roughly over Hood River, OR, facing south. Strong west winds over the Cascades form the mountain waves seen here and Gary has been up to around 35,000 ft on more than one occasion using the lift provided by these mountain waves.