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Avalanche Forecast

Archived

Jan 16th, 2025–Jan 17th, 2025

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

Regions

Glacier.

We have yet to see if/where Thursdays storm may have tipped the scales, making previously buried surface hoar reactive to skiers and riders.

Ease your way into terrain, as you assess the effect this wind event has had on the upper snowpack.

Confidence

Moderate

Avalanche Summary

On Thursday, there were several large (up to size 2) natural avalanches in the steep terrain on the N face of Mt MacDonald.

On Monday, a skier triggered a size 3 avalanche in Lone Pine. This ran ~1000m and accumulated significant mass.

Snowpack Summary

Up to 10 cm of new snow came in with Extreme SW winds on Thursday. Expect wind effect to be lower on slopes than usual, and potentially into typically sheltered terrain.

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. Where the upper snowpack has stiffened into a slab, this layer could be triggered by the weight of a skier.

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

Weather Summary

Temperatures plummet, as arctic air moves in to our area.

Tonight Clear periods. Alpine low -16°C. Gusty moderate-strong Northwest ridgetop winds.

Fri Sun/cloud/isolated flurries. Alpine high -15°C. Moderate gusty North wind.

Sat Mostly sunny. Alpine low -19°C, high -18°C. Light East wind.

Sun Sunny. Alp low -18°C, high -13°C. Light East wind.

Terrain and Travel Advice

  • 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.