Avalanche Forecast

Issued: Jan 1st, 2017 4:33PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Forecast weather for Wednesday and Thursday is 'up in the air' for now! Pay close attention to weather conditions and forecasts. With low-density snow available for transport, more wind can change the avalanche danger quickly.

Summary

Weather Forecast

A Strong upslope system eases into an Arctic High Pressure.Sunday night: Light snowfall, moderate NE winds.Monday: AM flurries, -24 at Treeline. Moderate Easterly winds slowly easing.Tueday: Clear and cold (-20), Light Easterly winds.Wednesday: Warmer (-15). Increased winds likely, but speed and direction differ greatly between forecasts.

Snowpack Summary

Upto 20cm of new snowfall has been reverse loaded by North-East winds onto South and West facing lees; forming soft, easily triggered Storm Slabs over hard surfaces. Snowfall with light winds on Sunday night will make these hard to spot. Elsewhere, stubborn Wind Slabs are now buried. Down 60 - 100 cm is a thick facet layer, of varying sensitivity.

Avalanche Summary

No observations were attempted in poor visibility on Sunday.On Saturday, debris from several large (Size 2) slab avalanches were observed. These were all in the South-West of the park, which received the highest snowfall totals Thursday night. One Wind Slab on Mt Rowe stepped down to the December 9 Persistent Weak Layer (facets).

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Problems

Storm Slabs

These are touchy, especially to the immediate lee of ridges. Look for these on the opposite side of features from normal. The storm snow will be slow to stabilize, due to cold temperatures. Wind Slab problems may develop on Wednesday.

Avoid travelling in areas that have been reverse loaded by winds.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

The weak midpack facet layer is widespread, but highly variable slab thickness and sensitivity makes these hard to evaluate. These are difficult to trigger, but may be large. Rocky, wind-exposed areas are most suspect.

Avoid shallow snowpack areas where triggering is more likely.Ride slopes one at a time and spot for your partners from safe locations.

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

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 2nd, 2017 4:33PM