Avalanche Forecast

Issued: Mar 20th, 2014 7:19PM

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

Tim Haggarty, Parks Canada

Waterton Lakes.

Enjoy the good skiing but take the time to carefully evaluate the new storm slabs as you enter new terrain. The snowpack changes rapidly with subtle changes in aspect and elevation.

Summary

Weather Forecast

After dropping about 15-20 cm the pacific air will be pushed out of the Park by arctic air Friday with temperatures dropping to near -20. This high pressure system will dominate Saturday. Pacific air will challenge the arctic air reaching the divide on Sunday which may result in limited snowfall. Expect variable wind direction and speed.

Snowpack Summary

10 cm new snow in the past 24 hrs. The 0314 interface is down 25 to 40 cm and is a crust below 1900m. The 0318 suncrust is 20 cm deep on solar aspects. Storm slabs have formed over these interfaces with mild temperatures and strong West winds. The 0310 rain crust is down 70 cm at Treeline and can be found as high as 2300m.

Avalanche Summary

Loose moist activity has diminished with dropping temperatures however loose dry activity can still be expected out of very steep terrain. Skiers at treeline elevations experienced cracking and small slabs failing in wind effected areas: a sign that storm slabs will be active to skier triggering in steep or unsupported terrain.

Confidence

Wind speed and direction is uncertain

Problems

Storm Slabs

Recent snow combined with mild temperatures and West winds have created soft slabs. These slabs are sitting on a variety of surfaces including rain crusts, sun crusts, old wind slabs and the interface to the previous storm snow and are 25-40 cm deep

Dig down to find and test weak layers before committing to a line.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Dry

New snow is sluffing off of very steep terrain and moving with skiers on steep slopes. Manage your group carefully and be aware of your sluff. Avoid confined terrain features such as gullies where these small slides could focus and gain more energy.

Avoid travelling on ledges and cliffs where sluffing may have severe consequences.Sluffs may trigger deeper instabilities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

As the snowpack cools this week it is gaining strength. The weak layer from early Feb may still be an issue but this is likely limited to thin areas at higher elevations under current conditions.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Mar 23rd, 2014 4:00PM