Today is wet in the west, with better weather in the east, but by the end of the working week MetService is forecasting a reversal of that split.

Heavy rain is forecast this weekend for the Bay of Plenty, Gisborne and Hawkes Bay, through to Wairarapa and Marlborough.

The heaviest and most prolonged falls are expected in the Eastern Bay of Plenty and northern Gisborne, and a heavy rain Watch is already in effect for these areas, with future warnings likely.

Christchurch is gearing up for the Super Rugby final on Saturday evening, and although it will be overcast with rain developing later that night, the odds are good for the match playing out before the worst of the weather sets in.

However, a small shift of wind direction could change the onset of the rain by several hours, so spectators are reminded to check metservice.com on the day for the latest updates.

'Winds are currently from the northwest, with a slow moving low pressure sitting to the southwest of the country,” says meteorologist Tom Adams.

'This low gradually slides across New Zealand over the next few days, turning the winds clockwise around to easterlies on Sunday.”

This means that, in contrast to the east, the western and southern parts of the South Island are set to see the best weather this weekend, with bluebird conditions for the Southern Lakes ski fields.

The clear skies will mean frosty mornings, especially for central Otago, so please take care on the roads.

Looking ahead to next week, the slow-moving low finally pulls away on Tuesday and winds turn northwest ahead of another trough, with unsettled conditions continuing through the week.