Snow Forecast for Canterbury High Country and Plains
A depression is moving over the country today with one low pressure centre east of the country and another remaining in the Tasman Sea. Airflow will tend much colder southerly from tonight as an anticyclone develops in the south Tasman Sea and extends a ridge of high pressure into the Southern Ocean. This will combine with the departing depression, and bring a strong very cold southeasterly airflow from Antarctic seas onto the country tomorrow and Friday. On Saturday a ridge of high pressure should move over the far south, while another trough develops in the Tasman Sea. A southwesterly airflow will prevail on Sunday and Monday with the next trough due about Tuesday.
We continue to expect a major snow event for the Canterbury Plains and High Country, with heavy accumulations of snow now expected to be confined mostly above 200m. Above this level expect 40-60cm of snow to fall tonight and tomorrow, with the heaviest falls early hours of tomorrow morning and again early afternoon. 60-80cm is likely above 400m. Below 200m precipitation will fall mostly as sleety rain, with 40-60mm likely and the potential for flooding.
Snow falls may be a little lighter in South Canterbury with perhaps 20-40cm there. Inland parts of North Canterbury have a risk of 80-100cm of snow above about 400m for the storm.
On Friday and early Saturday further snow showers or flurries are likely with another 10-20cm likely to accumulate above 200m, and possibly some snow showers to near sea level.
Temperatures will be very cold through this period with strong to near gale force winds from tomorrow lunchtime through Friday morning bringing significant wind chills. Wind chill equivalent temperatures of -10degC are likely. These will be hazardous and challenging conditions over the next few days, so please take care.
We will update again tomorrow if there is any significant change.