The warning comes after one skier was killed and another buried for seven minutes before being rescued in separate incidents in the South Island this week.
MSC chief executive Mike Daisley said the "unique combination" of a complex snowpack, incoming fine weather and anticipated high interest in back country skiing and snowboarding had prompted the organisation’s special warning ahead of the weekend.
"In the current high-uncertainty, high-consequence environment, the best course of action is to avoid avalanche terrain entirely, unless you have carried out a thorough investigation and have full confidence in the stability of the snowpack."
Since the beginning of September, an intense and prolonged cycle of westerly storm systems has delivered significant snowfall to alpine areas throughout the South Island, accompanied by high winds and fluctuating freezing levels.
"As a result of unseasonal, extended spring storm systems, we now have a highly complex and rapidly changing snowpack throughout most of the Southern Alps", Mr Daisley said.
"The storm systems, which are far from typical for this time of year in New Zealand, have created a variable and challenging snowpack. With this recent changeable weather comes the potential for dangerous weak layers within the snowpack, which can persist for days after the last snowfall", he said.
"The recent serious avalanche incidents, in both the Wānaka and Mid Canterbury back country, highlight the substantial dangers associated with back country travel in avalanche terrain at present."
As of yesterday afternoon, the NZ Avalanche Advisory (NZAA) categorised all Southern Lakes mountains in its coverage area as having a "considerable" avalanche risk and encouraged conservative decision-making.
On Monday in Wānaka, a party of five had been travelling in a back country area known as the "Commitment Chutes" when one person was buried by an avalanche.
The group, who were trained in avalanche rescue techniques, managed to extricate the victim within seven minutes, preventing any injuries.
On Wednesday, a guided heli-ski group were caught up in an avalanche on Pito Peak in the South Ashburton Range, resulting in one fatality.
Mr Daisley said the MSC highly recommended all back country snow enthusiasts stay updated on the latest avalanche advisory by following the NZAA Instagram and website.
"This is a time for seriously heightened awareness and care in the back country. Proper preparation and informed decision-making are critical."
