Heavy rain is expected to hit the South Island, putting the dampener on plans for the long weekend. MetService has issued severe weather warnings across parts of New Zealand, with heavy rain forecast from Sunday morning. Orange warnings are in place from Sunday for Fiordland, Westland, Buller, Tasman, the Richmond Range in Nelson/Marlborough and Bryant Ranges, including the Rai Valley in Marlborough. Up to 600 millimetres of rain could fall in some areas by Tuesday.  MetService says flooding, slips and dangerous driving conditions were possible, with more warnings likely for the North Island early next week. Fiordland, north of Charles Sound, could expect 100 to 150 mm of rain in the 12 hours from 6am on Sunday, with thunderstorms possible.  Up to 500mm was forecast to fall in Westland, south of Hokitika, from 2am on Sunday until 8pm on Monday.…