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Archived

Avalanche Forecast

Dec 21st, 2019–Dec 22nd, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

Great day to head to the local ski hills! Avoid avalanche terrain is the mantra for today.

Weather Forecast

The storm continues! Another 25cm+ are forecast to fall through today and into this evening. The freezing level should rise to 1600m today and then slip back down to 1000m this evening.

Snowpack Summary

60cm of storm snow now sits on 70cm of recent snow, which overlies the Dec 11th SH (5-12mm). This sits on a rounding midpack. The Nov 23 SH/Cr is down 160-185cm. Early season crusts still persist in the lower snowpack.

Avalanche Summary

A full round of artillery control East and West of Rogers Pass summit produced numerous avalanche up to size 3.5 all aspects and elevations. Slides were releasing in the storm snow then overloading the persistent slab of Dec 11, SH, down 80 - 100 deep. Larger slides may have dug down to the November crust but poor visibility prevented confirmation.

Confidence

Avalanche Problems

Storm Slabs

Warming temperatures are aiding in the formation of a touchy storm slab. This layer is expected to be widespread and sensitive to human triggering.

  • The new snow will require several days to settle and stabilize.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 3

Persistent Slabs

The Dec 11th Surface Hoar(SH), size 5-12mm is down 100cm+. This sliding layer was reactive in our control yesterday when overloaded by storm slab release. Large avalanches will be running to valley bottom.

  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Minimize exposure to avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3.5

Deep Persistent Slabs

The Nov 15 melt freeze crust is down deep in the snowpack. This layer may reach threshold for overload from avalanches triggered in upper snowpack layers. The resulting avalanches will be large.

  • Minimize exposure to avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2.5 - 3.5