Snow is expected on SH1 over the Desert Road this afternoon and this evening, the Metservice is warning.

Showers are expected to turn to snow above 800 metres between 4pm and midnight. One to four centimetres may accumulate.

Snow is expected on SH1 this afternoon.

Meanwhile a severe weather watch is in effect for significant snow down to 300m for Fiordland, Southland, and southern parts of Otago especially Clutha and Dunedin. Road snowfall warnings are also in place tonight and/or tomorrow night for the Desert Road, Lewis Pass, Porters Pass, Lindis Pass, and Milford Road.

The strong cold southwest flow which is bringing the snow should ease during tomorrow as a ridge of high pressure spreads over the South Island. Severe frosts are possible about inland areas overnight Tuesday to Wednesday, especially over the South Island.

The ridge recedes to the North Island on Wednesday.

At sea the Bay of Plenty can expect a 15 knot westerly today, rising to 20 knots everywhere this afternoon and to southwest 25 knots gusting 35 knots this evening.

The wind is reduced in the east, 10 knots east of Matata, but 20 knots in the east this evening. Sea is expected to become rough in the west this evening. Fine spells, fair visibility in occasional showers, clearing this evening.

Tomorrow: Southwest 20 knots, easing to southerly 10 knots in the evening. Fine. Wednesday: Becoming variable 5 knots in the morning. Fine.