Monday: Today that low pressure system is sitting to the NE of the country and will track to the SW today. Winds will be strong and from the NE. As the low tracks south tonight those winds will turn toward the east meaning resorts in that direction will probably do the best out of the system. : The snow level looks like it will be around 1400-1500m in Canterbury today lowering to around 1200m by tonight. The southern lakes will benefit from receiving colder air sooner with the snow level set to remain below 1200m for most of today. The North Island should see snow levels lower to 1200m tonight as the low pulls in cold air from the NW.
Snow. A widespread 15-20cm for Canterbury by tomorrow morning above 1400m, with the best accumulation around the easterly resorts (Mt Hutt and Porters). A similar amount for Mackenzie. Southern Lakes should see 10-15cm today above 1200m. 10cm on the North Island.
Tuesday: After tracking SE the low looks like it retract back to the north will be steered to the courtesy of our jet stream friend. Snowfalls to continue except it looks like it will be more of a Canterbury day as the bulk of the precipitation lies over the central South Island. Winds will be strong and from the east in Canterbury, moderate but gusty elsewhere. Snow level will remain below 1400m in Canterbury, 1000m for the Southern Lakes.
Snow. Another 20-30cm for Canterbury during Tuesday above 1400m, again with the best accumulation around the easterly resorts (Mt Hutt and Porters). 15-25 for the Mackenzie. The Southern Lakes resorts may be a little bit too far south to receive a lot of moisture but should still pick up another 5-10cm above 1000m. Dry on the North Island.
Wednesday: The low will begin to head further north, drying out a tad however that won't mean an end to snow falls. Central Canterbury will once again be the sweet spot for more snow. Winds strong in Canterbury, moderate elsewhere. Snow level will remain below 900m for most of the South Island.
Snow: 5-15cm for Canterbury, basically because a lot of the precipitation will be variable. The North Island, Mackenzie and Southern Lakes are a bit too far out of the firing line, doubtful we will see much there.
Thursday/Friday: This low just will not move, more snow for Canterbury particularly in the northern part of the State/Provence whatever you kiwi's call it. Winds will be moderate and from the NE. A cloudy day elsewhere and cold.
Snow: could see another 10-20cm in Canterbury on these two days, this will change a bit as we get closer.
Saturday: The precipitation looks like it will clear on Saturday however it will still be a mostly cloudy day with light winds.
Sunday: Precipitation could redevelop as a low may move back over the country, still a bit too far out for snow predictions.
Looking Ahead: The weather system that is set to deliver snow over the next few days is not your typical cold front and polar low. In fact it is tropical/subtropical moisture meeting cooler air from a cut off cold pool. This is very similar to the types of systems we had in 2008 where Mount Hutt and the North Island resorts did very well, whereas Southern Lakes/Mackenzie did ok. What is really needed is a prolonged negative Southern Annular Mode (SAM) phase. This tends to bring stronger westerlies and frequent cold fronts. The current system is actually the opposite, with strong easterlies.
The SAM is predicted to turn back positive after a more neutral phase over the last few days. Extended charts are suggesting that whilst the high pressure systems won't dominate they will certainly ridge out a lot of the low pressure systems, cutting off the cold air supply. After this week I would say we could see a period of sunshine punctuated by these borderline snow low pressure systems, certainly not the strong cold front we are after for the Southern Lakes.