Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 4th, 2023–Jan 5th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Purcells, Dogtooth, East Purcell.

Large avalanches were triggered by skiers and riders on several buried weak layers over the past week. Stay disciplined and make conservative terrain choices.

Confidence

Moderate

Avalanche Summary

After a dynamic period of natural and human-triggered avalanches earlier this week, reports of new avalanches have started to taper. However, with little change in the snowpack structure triggering large persistent slab avalanches remains a concern. Human-triggered avalanches are still likely in alpine and treeline terrain, especially in steep, shallow rocky areas. This notable avalanche continues to provide evidence that the layers described in the snowpack summary are with us for a while.

Snowpack Summary

Roughly 40 cm of recent snow has settled into a slab that overlies weak faceted grains. The snow is also stressing buried weak layers, including:

  • A surface hoar layer buried in mid-December that is 40 to 60 cm deep

  • Weak faceted snow and decomposing crusts near the bottom of the snowpack, ranging from 70 to 150 cm deep.

These layers have produced large avalanches over the past week and need more time to strengthen.

Weather Summary

Wednesday Night

Mainly cloudy overnight, no precipitation. 5 to 10 km/h southeast wind, treeline temperature -7 °C.

Thursday

Mostly cloudy, a trace of new snow, 5 to 10 km/h south wind, treeline temperature -6 °C.

Friday

Cloudy with sunny periods, possible flurries, 10 to 15 km/h southeast wind, treeline temperature -5 °C.

Saturday

A mix of sun and clouds, increasing through the day, trace amounts of snow. 5 to 15 km/h south wind, treeline temperatures -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Choose conservative terrain and watch for clues of instability.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.