terminal aerodrome forecast
A TAF is a forecast that consists of a concise statement of the expected meteorological conditions at an aerodrome for a specific time period. A TAF contains information on the expected surface wind, visibility, weather and clouds as well as on expected significant changes to one or more of these elements during the validity period.
BELGOCONTROL (2010) homepage, Meteorology 
Two types of TAFs exist: the 'short' TAF (TAF FC) has a validity period of 9 hours and is issued every 3 hours while the 'long' TAF (TAF FT) has a validity period of 30 hours and is issued every 6 hours. (same source)