Canterbury National A front will bring heavy rain to parts of the South Island from later today with up to 400 millimetres predicted in some areas. MetService has issued orange heavy rain warnings for Tasman District northwest of Motueka, Buller, Westland and Fiordland north of Doubtful Sound. Up to 400 millimetres of rain could fall on the ranges in the Tasman District with peak rates of between 20 to 30 millimetres an hour. Buller and Westland could also expect between 200 and 300mm of rain, with chances of thunderstorms. MetService said the warnings meant streams and rivers might rise rapidly, and there could be surface flooding, slips and difficult driving conditions. Heavy rain watches were also issued for the Richmond and Bryant ranges, Grey District, and the Canterbury and Otago headwaters. There was a high change of Richmond and Bryant ranges upgrading to a warning, while a moderate chance for other areas.…