Question: are winds aloft agl or msl?
Answer: Heights in the FA are above mean sea level (MSL) unless stated as above ground level (AGL). Ceilings (CIG) are always AGL. WIND and TEMPERATURE ALOFT FORECASTS (FD) are 6, 12, and 24-hour forecasts of wind direction, speed, and temperatures for selected altitudes to 53,000 feet MSL at specified locations.