Avia Weather is a useful tool to quickly access and decode METAR and TAF reports. However, if you want to better understand the automatic decoding done by the app, you may want to learn how to read the raw METAR and TAF reports yourself. To learn more we recommend the following documents by the German Weather Service (DWD) and by the Australian Bureau of Meteorology (BOM):
English
German Weather Service
METAR / SPECI / TREND / TAF,
Meteorological Reports and Forecasts for Aviation
https://www.dwd.de/EN/specialusers/aviation/download/products/metar_taf/metar_taf_download.pdf?__blob=publicationFile
https://www.dwd.de/EN/specialusers/aviation/download/products/metar_taf/metar_taf_download.pdf?__blob=publicationFile
Australian Bureau of Meteorology
Australian Bureau of Meteorology
Three-hourly Aerodrome Forecast (TAF3)
http://www.bom.gov.au/aviation/data/education/TAF3-Brochure.pdf
http://www.bom.gov.au/aviation/data/education/TAF3-Brochure.pdf
German
Deutscher WetterdienstMETAR / TREND / TAF,
Wettermeldungen und -vorhersagen für die Luftfahrt