The Bureau of Meteorology has issued a severe thunderstorm warning with the possibility of flash flooding and damaging winds for the Hunter, Metropolitan, Illawarra, Central Tablelands, Southern Tablelands and parts of the South Coast, North West Slopes and Plains, Central West Slopes and Plains, South West Slopes and Australian Capital Territory forecast districts. Heavy rains and a potential storm are also expected to hit Sydney's CBD this afternoon. Here are the details.