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Avalanche Forecast

Archived

Feb 21st, 2023–Feb 24th, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Waterton Lakes, Waterton.

VERY COLD Wed/Thurs! Wind chills up to -45C. Keep days short and bring emergency layers.

Friday brings warmer temps and a return to SW wind. Evaluate fresh slabs on standard lees.

Confidence

Moderate

Avalanche Summary

No new naturals observed however poor vis today. Two significant whumps with cracking in a thin below treeline area, suspect windslab over a weakening crust and basal facets.

Thanks to all the great posts this week on the Mountain Information Network, keep it up!!!

Snowpack Summary

30-50cm storm snow since Monday with Mod-NE winds forming soft windslab in reverse loaded features at all elevations. This overlies a stiffer windslab from last week's wind events and the Mid-January crust interface that is now down 50-100 cm. Alpine and Treeline midpack is well settled and overlies basal facets and depth hoar, especially in thin areas. Below treeline, the Jan Crust overlies facets and depth hoar to ground.

Weather Summary

Wednesday

Alpine High: -28C, winds: NE 40 km/h, trace precip, sunny with some clouds

Thursday

Alp High: -30C, winds: NE 35 km/h, trace precip, sunny with some clouds

Friday

Alp High: -15C, winds: W 40 km/h, no precip, clear skies

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.