Avalanche Forecast

Issued: Feb 4th, 2018 4:00PM

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

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

The danger has been reduced to considerable, however human interaction with avalanches is still very likely on steep terrain and terrain uniform features.Our Wx stations are currently down, we are working on getting them back online ASAP.

Summary

Weather Forecast

A slight cooling and clearing trend is expected for Monday. The wind is also expected to die down and shift to the west. However, the moment of respite will be short lived. Another storm is expected to arrive midday on Wednesday bringing warm temps, precip and an increase in wind. We expect the danger to rise significantly at that time.

Snowpack Summary

Up to 40cm of storm snow (48hrs) and strong wind have created slabs that are primed for human triggering. The main concern in the snowpack continues to be the 3 persistent weak layers of surface hoar and/or facets that are found between 50 and 100cm down. We continue to observe sudden test results, whumphing and large propagations on these layers.

Avalanche Summary

Natural activity was directly observed across Bow Lake today. A cornice released off of a cliff and triggered the slope below it, size 2. An avalanche control operation produced 3 size 3 avalanches on West facing avalanche paths on 93N. The debris ran to mid run out. Additionally, evidence of a widespread cycle up to size 3 was observed.

Confidence

Due to the quality of field observations on Monday

Problems

Persistent Slabs

Three weak layers exist in the upper snowpack: Jan 16, Jan 6, and Dec 15. All are a mix of sun crust, surface hoar and facets depending on the aspect and elevation. Destructive avalanches have occurred on these and will continue over the few days.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3.5

Storm Slabs

20-40cm of storm snow (and wind) has developed a reactive slab at higher elevations. If triggered this layer has the potential to step down to deeper instabilities. Continue to make conservative route choices.

The new snow will require several days to settle and stabilize.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 5th, 2018 4:00PM