MetService have forecast inclement weather conditions across parts of the South Island on Friday (19 December), as a north westerly flow brings periods of heavy rainfall over alpine and headwater regions. Severe weather watches remain in force, with rainfall totals expected to approach warning thresholds during the advisory period.

• Periods of heavy rainfall with possible thunderstorms are forecast over the Ranges of Westland from 0500 hours to 1600 hours (local time) on Friday (19 December). Rainfall accumulations are expected to be significant and may reach warning criteria, with a moderate likelihood of escalation to a heavy rain warning.
• Sustained heavy rainfall with possible thunderstorm activity is expected across the headwaters of Canterbury lakes and rivers south of Arthur’s Pass during the same period. Rainfall is likely to be heaviest within approximately 15 kilometres east of the main divide, with freezing levels near 2,400 metres, increasing runoff potential.