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Avalanche Forecast

Mar 20th, 2017–Mar 21st, 2017
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
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

Regions: Sea To Sky.

The freezing level is forecast to rise in conjunction with snow and/or rain. This could be enough make any of the deeper buried weak layers reactive again in the coming days.

Confidence

Moderate - Freezing levels are uncertain on Tuesday

Weather Forecast

TUESDAY: Periods of snow, accumulation 10-15cm / Light to moderate south wind / Alpine temperature 0 / Freezing level 2000m WEDNESDAY: Flurries, accumulation 5-10cm / Light to moderate southwest wind / Alpine temperature -3 / Freezing level 1500mTHURSDAY: Flurries, accumulation 5-10cm / moderate to strong south wind / Alpine temperature -4 / Freezing level 1300m

Avalanche Summary

Recent reports indicate both natural and human triggered wind slab avalanches in alpine and tree line lee terrain to size 1.5. Earlier last weekend, explosive control and ski cutting produced numerous small storm slabs (size 1-1.5) and two size 2 storm slabs up to 50 cm deep. Most failed within the storm snow, but a few on the mid-March rain crust.On Tuesday, wind slabs may remain reactive in human triggers and at upper elevations the deeper mid-February weak layer continues to present a low likelihood of triggering yet would produce a large avalanche and thus a high consequence if triggered.

Snowpack Summary

Expect an additional 10-15cm of new snow through the day today to add to the 30 cm of storm snow from last weekend, which sits above a widespread rain crust up to 2200m. Thicker wind slabs and large cornices likely exist in alpine terrain. Reports suggest the storm snow is generally well bonded to the crust, and cooling temperatures should help stabilize the upper snowpack. The mid-February crust/facet layer is now 80-120 cm deep and may be up to 200 cm deep in wind loaded terrain. This layer was reactive prior to recent warming events, but now there's some uncertainty as to how long it will remain reactive.

Avalanche Problems

Wind Slabs

Recent southerly winds have created reactive wind slabs in the lee of terrain features
Use ridges or ribs to avoid pockets of wind loaded snow.Extra caution needed around cornices with current conditions.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

Warming temperatures and additional snow or rain has the potential to make deeper buried weak layers reactive.
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3