The MetService has a range of weather alerts in place as a significant spring storm comes in for the first part of the week.
Heavy rain, heavy snow and severe gales are forecast for parts of Canterbury.
Road snow warnings have been issued for alpine passes: the Lewis (State Highway 7), Arthur's and Porters (SH73) and Lindis (SH8) passes, as well as the Crown Range Road linking Queenstown and Wanaka, and the Milford Rd (SH94) in Southland.
A strong wind watch is in place today for the Canterbury High Country and for Banks Peninsula tomorrow from 2am to 10am.
The MetService says to expect strong southwest winds, approaching severe gale force in exposed places, on Banks Peninsula.
A heavy rain watch has been issued for the headwaters of the Canterbury lakes and rivers, south of Arthur's Pass, from 3pm to 10pm today.
Heavy rain may approach "warning criteria within 15km east of the main divide", the MetService says.
A heavy snow watch is also in place for the Canterbury High Country, south of the Rangitata River, from 8pm today until 5am tomorrow.
"Snow is forecast to lower to 400 metres, with heavy snow possible at higher levels. Snow amounts may approach warning criteria above 500 metres," MetService said.
The snow could reach South Island alpine highways over the next two days as the band of changeable, colder weather moves up the island today and tomorrow.
“If you are travelling through the alpine passes or further south later today or tomorrow, be prepared for snow and much colder temperatures,” said Tresca Forrester, Journey Manager for Waka Kotahi NZ Transport Agency.
“Take your time and take extra care particularly given it is the second week of the school holidays so drivers may be on routes they are not very familiar with."
Strong southerly winds are forecast for tomorrow. “Snowfall could be heavy for parts of Otago and Canterbury from tonight into Tuesday,” Ms Forrester said.
“Please check your route before you head off, carry extra supplies and chains if snow is a possibility."
The deepening low and active front is expected to cross southern New Zealand today, preceded by strong and moist northwesterlies and followed by a strong cold southerly change.
Milford Road closed
The Milford Road (SH94) closed at the East gate (Hollyford) and the Chasm about 1.30pm today due to the high risk of avalanche.
"The weather system is still currently moving through heavier and slower than expected which has increased our avalanche hazard to high," Milford Road/NZTA advised.
"The road will remain closed for the remainder of today and overnight with the possibility of reopening mid-morning subject to avalanche assessment."
Heavy rain with snow flurries were likely about the Homer Tunnel today, while Tuesday would see showers with more snow flurries possible near the tunnel at times and the freezing level lowering to 900 metres.
There is also a heavy snow watch for Central Otago and the Queenstown Lakes District, and a heavy rain watch for the headwaters of the Otago lakes. The forecaster says snow is forecast to lower to 400 metres, with heavy falls possible at higher levels. Snow amounts may approach warning criteria above 700 metres.
The MetService says the "very strong and cold south to southwest flow" would persist through until Wednesday or early Thursday, before a ridge of high pressure builds over New Zealand again.
- ODT Online and RNZ
