New Zealand Mountan Safety Council

Nelson Lakes

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Issued at 24/07/2016 7:18pm. Valid till 27/07/2016 6pm

Nelson Lakes

Mountain
Current avalanche advisory
High Alpine

Above 2000 meters

Alpine

1000 to 2000 meters

Sub Alpine

Below 1000 meters

Avalanche Danger Scale
Avalanche Danger Scale
Report TutorialPrint Reporthear report

Primary Avalanche Danger

Dangerous Aspects
high
Danger Rose
4
Highest Danger Rating
Likelihood
indicator
gauge
Certain
Likely
Unlikely
Size
indicator
gauge
Largest
Small
Trend
indicator
gauge
Increasing
No change
Decreasing
Time of day
clock
Time of day
All day
Alpine level
High Alpine: Above 2000m
Alpine: 1000 to 2000m
Low Alpine: Below 1000m
Description:
This danger will become high on the South Eastern half above 1800 metres during Saturday night. Large avalanches will be possible with some capable of reaching the valley floor. Continued snow and wind transportation from the west will overload the weakness that exists within the old snow. Total avoidance of this terrain is now required.

Secondary Avalanche Danger

Dangerous Aspects
high
Danger Rose
4
Highest Danger Rating
Likelihood
indicator
gauge
Certain
Likely
Unlikely
Size
indicator
gauge
Largest
Small
Trend
indicator
gauge
Increasing
No change
Decreasing
Time of day
clock
Time of day
All day
Alpine level
High Alpine: Above 2000m
Alpine: 1000 to 2000m
Low Alpine: Below 1000m
Description:
Heavy snow fall associated with strong to gale force winds will create a storm slab danger. Snow will quickly accumulate in aspects lee to the westerly half. Avalanches will be likely to occur around ridges crest and below cornice development. Storm slab avalanches may also act as the trigger to the persistent slab avalanche problem causing slopes to step down to the deeper weakness.

Recent Avalanche Activity

Recent Avalanche Activity
Large avalanches up to class 3.5 have occured on southern and southeastern aspects that were loaded during the last storm cycle. Estimated to have occurred on the 14th or 15th of July. These avalanches were caused by a very significant weakness within the old snow that will be very persistent.

Current Snowpack Conditions

Current Snowpack Conditions
There have been significant snowfalls early season during May. Over early June significant amount of rain fell to upper elevations in the park. Cold and clear conditions over the 2 weeks prior to the last storm cycle from the 13th to the 15th of July developed significant weak layers within the old snow on southern and eastern aspects above 1800 metres. The layer responsible for the occurrences outlined in the avalanche activity section are large loose faceted crystals with resilient ice crust above and below. The weakness will fail consistently using a range of shear tests. Total new snow in the last storm is 50 cm in the St Arnaud range and an estimated 80cm + in the south and west of the park associated with strong south west winds. Evidence of significant wind transport to aspects lee to the west is clearly evident meaning that large loads of new snow now sit above the identified weakness. This issue will be slow to resolve. Western half aspects have been wind scoured during the last storm and still don't have widespread deep snow cover below 1800m. Heavy snow fall associated with strong westerly winds will rapidly load lee aspects during the next 24 hours. Stay at home!

Mountain Weather

Mountain Weather
Snow down to 800m easing during Monday. Strong to gale force westerly winds. Freezing level at 1100m.


MetService
For more information go to: http://www.metservice.com/mountain/index

Forecast by Matt Wilkinson

Avalanche Forecast Regions:
Mountain Safety Council managed websites
Mountainf Safety Council websiteAdventure Smart websiteNew Zealand Avalanche Center