Northwest gales and heavy rain are expected across a large part of the country this weekend, says a MetService spokesperson.

"Fronts embedded in a strong northwesterly flow are expected to affect New Zealand this weekend."

Watches and Warnings are in force for heavy rain and severe gales.

"Note that the heaviest rain is likely to affect the west of the South Island and the headwaters of the lakes and rivers of Otago and Canterbury. 

A Heavy Rain Watch is in place for the following regions:

Waikato south of Te Awamutu, Waitomo, Taumarunui, Taupo, northern Taranaki and northern Taihape have a heavy rain watch in place, valid for 11 hours from 6pm Saturday August 31 to 5am Sunday, September 1. A period of heavy rain, and amounts may approach warning criteria. Localised downpours and thunderstorms are possible, and there is a moderate chance of upgrading to a Warning.

The ranges of eastern Bay of Plenty and Gisborne/Tairawhiti have a heavy rain watch in place for 24 hours from 12pm Saturday August 31 to 12pm Sunday September 1. Expect periods of heavy rain, and amounts may approach warning criteria. Rain is expected to ease for a time overnight Saturday with thunderstorms possible.

The Richmond and Bryant Ranges including the Rai Valley have a heavy rain watch in place for 11 hours from 4pm Satrday August 31 to 3am Sunday, August 1.  A period of heavy rain, and amounts may approach warning criteria.

Tasman northwest of Motueka, Grey and Buller districts have a heavy rain watch in place for 12 hours from 1pm Saturday, August 31 to 1am Sunday, September 1.A period of heavy rain, and amounts may approach warning criteria. Thunderstorms possible.

"Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible," says a MetService spokesperson.

"Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously."

The ranges of the Westland District from Haast southwards also have a heavy rain watch in place, valid for 19 hours from 2pm Sunday, September 1 to 9am Monday, September 2. A period of heavy rain, and amounts may approach warning criteria. Further heavy rain likely from late Monday.

Fiordland has a heavy rain watch in place for 18 hours from 12pm Sunday, September 1 to 6am Monday, September 2.  A period of heavy rain is expected from Sunday afternoon and amounts may approach warning criteria. 

The headwaters of the Otago lakes and rivers also have a heavy rain watch in place, for 19 hours from 2pm Sunday, September 1 to 9am Monday, September 2.  A period of heavy rain is expected from Sunday afternoon and amounts may approach warning criteria.
High chance of upgrading to a Warning.

A Strong Wind Watch is in place fror Taranaki, Taihape, northern Whanganui and inland parts of Hawke's Bay and Gisborne/Tairawhiti, Wellington and Kapiti Coast. Tasman District and the Marlborough Sounds, Otago excluding coastal parts of Clutha, Southland north of Gore and Fiordland.

"Please keep up to date with the latest forecasts as regions may be added or upgraded," says a MetService spokesperson.