A TAF is the international standard code format for terminal forecasts issued for airports. TAFs are valid for a 30 hour time period and are issued 4 times a day at 6 hour intervals. The forecast includes forecasted wind speed, wind direction, visibility, ceiling, type of precipitation (i.e. snow, rain, etc.) and/or weather phenomenon.
A Terminal Aerodrome Forecast (TAF) is a concise statement of the expected meteorological conditions significant to aviation for a specified time period within five statute miles (SM) of the center of the airport’s runway complex terminal). The TAFs use the same weather codes found in METAR weather reports (Section 2) and can be viewed on the National Weather Service (NWS) Aviation Digital Data Service (ADDS) Web site at: http://adds.aviationweather.noaa.gov/tafs/.
Support for TAFs.
http://www.aviationweather.gov/taf/help
AC 00-45G - Aviation Weather Services (7.2 Terminal Aerodrome Forecast (TAF) - Page 7-19) - https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/215166
Also see http://www.aviationweather.gov/static/help/taf-decode.php and Aeronautical Information Manual (AIM) page 7-1-61 (https://www.faa.gov/air_traffic/publications/#manuals)