Avalanche Forecast

Issued: Feb 22nd, 2019 3:28PM

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

Avalanche Canada shorton, Avalanche Canada

Fresh wind slabs may be forming at higher elevations, but the main concern is still persistent slabs at lower elevations.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

FRIDAY NIGHT: 5-10 cm of snow, moderate southwest wind, alpine temperatures drop to -12 C.SATURDAY: Mix of sun and cloud with isolated flurries and localized accumulations of 5 cm, light wind, alpine high temperatures around -10 C.SUNDAY: Sunny with cloudy periods, light wind, alpine high temperatures around -10 C.MONDAY: Mix of sun and cloud with light flurries in the afternoon, light northeast wind, alpine high temperatures around -12 C.

Avalanche Summary

Activity on Thursday was limited to sluffing in steep terrain and some isolated whumpfing on south aspects.Human triggered avalanches were reported everyday between February 12 and 20. Although most avalanches were small (size 1-1.5), some have shown impressive propagation (see some examples here and here).On Tuesday, a notable size 3 persistent slab avalanche occurred on an east aspect between 1800-2100 m. This avalanche was triggered by explosives and it reportedly failed on the persistent weak layer that was buried on February 7th.

Snowpack Summary

A weak storm has brought 10-25 cm of low density snow that now covers variable wind slabs at higher elevations and sun crusts on south-facing slopes.A weak layer of surface hoar (feathery crystals) and a crust that was buried on February 7th is now 30-50 cm deep. This layer has been reactive, and has produced avalanches as large as size 3. Two other surface hoar layers are buried 50 to 80 cm deep the snowpack (referred to as the February 1st and mid-January layers). Although they have not been reactive recently, they are still being monitored by professionals. These layers are most prevalent below treeline on shady aspects. The lower snowpack is considered generally strong.

Problems

Persistent Slabs

An icon showing Persistent Slabs
It remains possible to trigger an avalanche on one of the surface hoar or crust layers buried 30 to 80 cm deep. These layers are most prominent at treeline and below.
Use caution on open slopes and convex rolls Caution around sheltered open areas at treeline and below including cutblocks, gulleys, and glades.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Wind Slabs

An icon showing Wind Slabs
Fresh wind slabs are possible to trigger at higher elevations. Old wind slabs also linger on a variety of aspects.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 23rd, 2019 2:00PM