High mountain summits often reach into strong wind, which can make the launch and flight challenging, or just plain inconceivable. As forecasts improve though it is getting easier to spot a light-winds-aloft window setting up a few days out. But planning and executing a flight off a high mountain still requires careful evaluation of wind strength at the upper, mid and low levels.
Acceleration and stagnation zones
Launch spots on a ridge or summit will experience localised acceleration of flow. This can double the wind on launch when compared with wind at the same level away from the mountain.
Upwind stagnation zones do the opposite and can give the impression of a launchable breeze while the true wind is far stronger. These stagnation zones are pronounced from 50 to several hundred metres down the upwind side depending on the topography. If you are below the summit on the upwind side of...
