Archived

Avalanche Forecast

Apr 11th, 2017–Apr 12th, 2017

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

1: Low

The avalanche danger rating below treeline will be low

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

2: Moderate

The avalanche danger rating below treeline will be moderate

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

1: Low

The avalanche danger rating below treeline will be low

Regions: South Rockies.

Significant uncertainty surrounds snowfall amounts on Wednesday-Thursday. If you see more than 25cm fresh snow, danger ratings will be CONSIDERABLE. Limit your exposure to cornices when it's cloudy and completely avoid them when it's sunny.

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

There's significant uncertainty surrounding precipitation on Wednesday-Thursday (wide range given), and then some clearing for Friday. WEDNESDAY: Flurries late morning into the afternoon (5-10cm). Moderate southerly ridgetop winds. Freezing level around 1700 m.THURSDAY: Snow continues Wednesday overnight with 5-20cm possible by Thursday afternoon. Moderate southwest ridgetop winds. Freezing level around 1900 m.FRIDAY: Clearing Thursday overnight and then cloudy by Friday afternoon. Strong southwest ridgetop winds. Freezing level around 1800 m.

Avalanche Summary

On Tuesday, two recent storm slab avalanches (35cm crown, Size 2) were observed in steep north facing terrain near Elkford at 2400m elevation.

Snowpack Summary

Over the past few days, 15-30cm of new snow fell above treeline with southerly winds. The sun on Monday & Tuesday made snow surfaces moist and unstable during the day, but it should stabilize quickly after an overnight refreeze (in most areas forming a crust on all aspects up to 2300m).Cornices remain large, looming, and are best avoided.The mid snowpack is well settled and continues to transition into a spring snowpack, becoming isothermal at treeline in some areas and below treeline in most areas.The bottom third of the snowpack is composed of weak facets, but this deep persistent weakness has not been reactive for several weeks. That said, a large trigger like a cornice, or rapid warming of the snowpack could potentially trigger this layer.

Avalanche Problems

Cornices

Solar radiation and daytime warming are common cornice triggers. Limit your exposure when it's cloudy and completely avoid cornices when it's sunny.

Minimize exposure to overhead hazard from cornices.Give cornices a wide berth when travelling on or below ridges.Cornices become weak with daytime heating, so travel early on exposed slopes.

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 2 - 3

Wind Slabs

New snow and moderate southwest winds have formed thin wind slabs below alpine ridgetops.

Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with elevation.Avoid freshly wind loaded features.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2