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Archived

Avalanche Forecast

Apr 17th, 2012–Apr 18th, 2012
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
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
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
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: Kootenay Boundary.

Confidence

Fair - Due to limited field observations for the entire period

Weather Forecast

Gusty westerly winds are expected to develop overnight and rain showers and flurries should start by mid-day and continue into Wednesday night. Thursday is forecast to be unsettled with gusty southwest winds and periods of rain showers and flurries at higher elevations. The next Pacific frontal system is forecast to move into the interior by early Friday morning. Expect 5-10 mm of precipitation combined with overnight freezing levels down to about 1500 metres.

Avalanche Summary

Spring conditions exist in the region. Exposure to the sun, warm temperatures, and periods of rain are the most likely factors to influence the avalanche danger. If the temperatures go below freezing overnight, strong crusts should develop that are likely to hold the snowpack together. If the sun shines for a few hours, the crusts may break down quickly and moist surface snow avalanches may start running naturally. Continued warming from more sun, rain, or no overnight freeze, may cause surface avalanches to step down and trigger deeper wet slab avalanches. Prolonged warming may cause very deep releases on weak layers that were deposited early in the season, or on depth hoar that developed during the winter. It is important to monitor the temperature and the freezing levels as they may change rapidly from day to day.

Snowpack Summary

As we transition into spring the surface layers have a great deal of influence on the snowpack. When there is a solid re-frozen surface crust, travel is fast and easy, and the snowpack is held together by the surface cap. Any deeper persistent weak layers are unlikely to fail until the surface cap breaks down from daytime heating. When there is no crust, any deeper weak layers may fail depending on the amount of heat and the triggering force that is applied. If it cools off and snows, new snow and windslabs may not bond well to the hard spring crusts.

Avalanche Problems

Loose Wet

Loose wet avalanches are expected during periods of daytime warming and during periods of rain showers. Overnight freezing above about 1500 metres should develop a hard crust that may deteriorate during the heat of the day.

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

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 5

Wet Slabs

Wet slab avalanches are expected during periods of daytime warming and during periods of rain showers. Overnight freezing above about 1500 metres should develop a hard crust that may deteriorate during the heat of the day.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 3 - 7

Wind Slabs

New snow may be transported into wind slabs that are easy to trigger on northerly aspects in the alpine.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood: Likely

Expected Size: 1 - 4