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Avalanche Forecast

Archived

Feb 15th, 2023–Feb 16th, 2023

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

Regions

Purcells, Dogtooth, East Purcell, St. Mary, West Purcell.

The best way to manage a complex snowpack like the one in this region is to stick to smaller, low consequence terrain. Don't let your guard down as large persistent and deep persistent slab avalanches are still being reported every two or three days.

Confidence

Moderate

Avalanche Summary

A veritable smorgasbord of natural and explosives triggered in addition to skier controlled avalanches continue to be reported from the region. From smaller wind slab avalanches to large persistent slab avalanches and even a few cornice failures. This speaks to the complexity of the snowpack in this region and the potential for an avalanche on any given day.

This MIN from Grizzly Bowl west of Golden illustrates the potential for cornice failures and their ability to trigger larger slabs.

Snowpack Summary

15-40 cm of of recent storm snow has been variably distributed by winds and is settling above a layer of surface hoar, facets, and/or crust. This layer has become reactive in the southern and western parts of the Purcells, where it is more deeply buried. A new sun crust could be present on steep south aspects at treeline and below.

The lower snowpack contains a widespread layer of large, weak facets that is typically 80 to 150 cm deep. Snowpack depths at treeline range between 80 and 200 cm, with the shallowest depths found on the eastern edge of the Purcells.

Weather Summary

Wednesday night

Mostly clear. Winds from the west and southwest 20 km/h. Temperature -15˚C in the alpine.

Thursday

Starting clear with clouds increasing into the afternoon. Flurries beginning late in the day bringing 5 cm of new snow. Wind 15 km/h from the southwest. Temperature -10˚C.

Friday

A mix of sun and clouds. Flurries delivering 5 cm of new snow. Wind 10 km/h from the west. Temperature -8˚C.

Saturday

Cloudy. 5-10 cm of new snow. Wind 10km/h from the west. Temperature -9˚C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use careful route-finding and stick to moderate slope angles with low consequences.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
  • Avoid steep convex slopes.
  • Be especially cautious as you transition into wind affected terrain.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.