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Avalanche Forecast

Archived

Jan 15th, 2025–Jan 16th, 2025

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

Regions

Glacier.

With a buried weak layer and a building surface slab,

Thursday will be a good time to take it easy.

Confidence

Moderate

Avalanche Summary

Skier triggered sz 3 in Lone Pine Monday, ran ~1000m and accumulated significant mass.

Several natural avalanches to sz 2.5 were observed Monday afternoon, triggered by solar input on S through W slopes.

There have been several reports of rider triggered avalanches up to size 1 in terrain adjacent to Glacier National Park.

Snowpack Summary

A complex upper snowpack will be increasingly challenging to manage with incoming wind and snow.

New snow will cover facetted snow or pockets of windslab in exposed areas. 30-40cm down, there is a weak interface (Jan 7th layer) of surface hoar into the high alpine, and a thin crust on steep S aspects. As the surface stiffens into a slab, expect increasingly large avalanches on this Jan 7th layer.

Overall the mid and lower snowpack is strong and well settled.

Weather Summary

A brief pulse of snow and strong wind Thursday, followed by plummeting temps.

Tonight Clear periods. Alpine low -6°C. Moderate SW ridgetop winds.

Thurs Flurries, up to 10cm. Alp high -6°C. Gusty strong-extreme West wind.

Fri Sun/cloud/isolated flurries. Alp low -16°C, high -11°C. Moderate gusty North wind.

Sat Mixed sun and cloud. Alp low -20°C, high -15°C. Light N wind.

Terrain and Travel Advice

  • Minimize exposure during periods of heavy loading from new snow and wind.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks, or recent avalanches.
  • Be especially cautious as you transition into wind-affected terrain.

Problems

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.

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.