Avalog Join
Archived

Avalanche Forecast

Feb 7th, 2015–Feb 8th, 2015
Alpine
4: High
The avalanche danger rating in the alpine will be high
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
4: High
The avalanche danger rating in the alpine will be high
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Storm problems will persist on Sunday, especially at higher elevations. If the sun breaks through, solar triggered avalanches are expected. Conservative decision making remains critical and travel in avalanche terrain is not recommended.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Another pulse of moderate-to-heavy precipitation is expected Saturday overnight with freezing levels around 1800m. Precipitation should ease during the day on Sunday but light scattered flurries are expected to persist, at least in the morning. Broken or scattered sky cover is possible in the afternoon and some areas may see sun. Freezing levels should remain around 1800m. Alpine winds are forecast to be strong from the SW on Sunday morning and ease during the day. The next storm pulse is expected to arrive Sunday overnight and persist through the day on Monday. Freezing levels may drop Sunday overnight but this depends on the amount of clearing between the storm pulses. Freezing levels on Monday are uncertain and may be as low as 500m or as high as 1500m. The end of the storms is forecast for early Tuesday. Lingering flurries and sunny breaks are both possible on Tuesday. Unfortunately, the warm air is expected to persist for several days following the end of the storm and freezing levels may remain unseasonably high.

Avalanche Summary

Natural, human-triggered, and explosive controlled avalanches up to size 2.5 were reported on Friday. This activity is expected to have continued on Saturday. On Sunday, natural avalanches remain likely at upper elevations where storm and wind loading continue. At lower elevations which have seen rain, natural activity is less likely but remains possible. Human-triggering remains very likely at higher elevations on Sunday. If the sun comes out on Sunday, solar aspects will likely see natural avalanche activity.

Snowpack Summary

Up to 60cm of recent storm snow has fallen over the late-Jan weak layer. Rising freezing levels during the storm have created upside-down snow conditions and highly reactive storm slabs. Rain has soaked the snow surface up to around treeline elevation. Strong SW winds have formed wind slabs in exposed leeward terrain features. The storm slab sits on an old rain crust at lower elevations, variable surface hoar, and/or wind affected surfaces at higher elevations. The mid-January surface hoar is typically down 60-100cm but may have been destroyed by warmth at low elevations. The mid-December weak layer is in the mid-pack down 80 to 120cm. Both of these persistent layers have been reactive recently. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It has been unreactive lately, but should remain on your radar, especially in shallow snowpack areas.

Avalanche Problems

Storm Slabs

Strong winds, heavy snowfall, and high freezing levels have created widespread storm slabs at higher elevations. Continued storm conditions will add to these highly reactive slabs.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 2 - 5

Persistent Slabs

Buried persistent weak layers may be over-loaded by the new storm loading and become reactive. There are multiple weak layers in the mid-pack. A dormant deep persistent weakness near the ground has the potential to wake-up with the additional load.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 5

Wet Slabs

Continued rain at lower elevations may result in wet slab avalanches running to valley bottoms. Loose wet avalanches are expected from steep terrain features.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 5