Alyeska is a lee-side thermal site and one of the few places to fly in southcentral Alaska with East winds.  Chugach mountain tops protect Girdwood valley allowing thermal activity, though when winds turn NE, rotor conditions can be quite rowdy. Winds in nearly all directions are all flyable, though SW light winds tend to break up the valley thermals. Often, down-valley flow off the glacier at the top of the uppermost ski lift will create 90-degree cross winds on the north and south (tower 10) launches which appear to be east winds.  Attempt this only if your launching skills are strong and the prevailing wind is not east or even northeast.