Archived

Avalanche Forecast

Dec 19th, 2017–Dec 20th, 2017

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

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Skier or Rider triggered avalanches are likely today. Now is a good time to step back and make conservative terrain choices.

Weather Forecast

A Low-Pressure system slides South of Rogers Pass, while a large High-Pressure moves in from the NE. As these two weather patterns duke it out, we'll accumulate 5-10cm of new snow, moderate Northerly winds and cold temperatures in the -10 range. 5cm tonight and plummeting temperatures into the future as the High-Pressure dominates our region.

Snowpack Summary

40cm of storm snow now overlies the Dec 15th Surface Hoar/Persistent Weak Layer. On steep solar aspects, there is a sun crust also buried under the new snow, reaching well into the Alpine from last week's inverted temperatures. Throughout the snowpack there are multiple crusts, which are currently bonded well to neighboring layers.

Avalanche Summary

A Widespread natural avalanche cycle occurred yesterday morning up to size 2.5 in the highway corridor. Avalanches were mainly size 1.5 to 2 and all failing as a soft slab on the Dec 15th Surface Hoar Layer. Avalanches initiated on all aspects and elevations yesterday, see attached pic of a below tree line slab avalanche. low elevation avalanches

Confidence

Due to the number and quality of field observations

Avalanche Problems

Storm Slabs

Yesterday's storm snow is settling into a slab. It will be reactive in windy areas in the Alpine and exposed areas at Tree Line. Steep solar asp will be problematic, as there will be a crust under our slab and a Surface Hoar/Facet combo BTL.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.Use conservative route selection, stick to supported terrain features, avoid overhead hazards.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3