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Archived

Avalanche Forecast

Dec 29th, 2017–Jan 1st, 2018
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Waterton Lakes.

Fresh, deep powder disguises a thin snowpack.  Be aware that where wind affect is obvious, danger may be higher than forecast ratings.  Rising temperatures and sun on cold loose snow may keep danger levels elevated heading into Monday.

Weather Forecast

Another large snowfall Friday night may double current storm snow totals.  Moderate NE winds possible for a short time overnight. Otherwise light winds are forecast; but pay attention as as any wind will up the danger.  Clearing trend on Sunday. Temperatures will remain in the -20's overnight and through Saturday, then rise to around -5 by Monday.

Snowpack Summary

35cm low density new snow (and increasing), with soft Storm Slabs lee to NE winds in highly exposed areas. Down 70cm is a layer of facets over a crust. This has been giving moderate and hard, sudden results in tests in Western areas. It seems most sensitive 1600-1900m, however these elevations are mainly below threshold snow depths for avalanches.

Avalanche Summary

Poor visibility limited observations on Thursday and Friday. Several small natural avalanches (loose dry and wind slab) were observed on NW-NE aspects on Wednesday, in steep terrain at and below Treeline. Widespread whumping and shooting cracks were noted from 1700-1900m, but all except lee areas had too many protruding stumps/rocks to avalanche.

Confidence

Forecast snowfall amounts are uncertain on Saturday

Avalanche Problems

Loose Dry

Deep surface snow with little cohesion is draped across the park.  A puff of wind, spike of sun, or your own wading could be enough to set it in motion.
Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Storm Slabs

Exposed areas saw wind transport Thursday night, and may do on Friday night also - just enough to set up isolated storm slabs in unusual (South and West facing) lee features.  These could be reactive; particularly on Saturday, and during midday sun.
Keep an eye out for reverse loading created by an upslope storm.Use caution in lee areas. Recent snowfall mixed with wind loading has created storm slabs.

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

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 2