Avalanche Forecast

Issued: Apr 7th, 2016 8:15AM

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

pmarshall, Avalanche Canada

Purcells.

Plan to start and finish your day early while the weather is very warm and sunny. Minimize your exposure to large sunny slopes and overhead hazard.

Summary

Confidence

Moderate

Weather Forecast

FRIDAY: Mainly sunny. The freezing level remains close to 3500 m and winds could rise to moderate or strong from the W-SW late in the day. SATURDAY: A mix of sun and cloud. The freezing level could drop to 2000 m and winds are generally light from the NW. SUNDAY: A mix of sun and cloud. The freezing level shoots up again to 2500 m and winds are light and variable.

Avalanche Summary

I suspect sunshine and rapidly rising temperatures set off a widespread loose wet cycle on steep sun-exposed slopes on Thursday. Some areas may have seen cornices popping off and perhaps isolated slab avalanche activity. Friday will be a very similar day in terms of weather. We could see loose wet sluffing taper off a little, but the potential for persistent slabs and cornices falls could be even higher as the snowpack warms even more.

Snowpack Summary

Sunshine and soaring temperatures may have resulted in moist or wet snow on all aspects and elevations, except possibly very high true-north slopes. The existence and strength of a surface crust will be important on Friday. If a crust doesn't form or it breaks down really early, then avalanche danger might stay elevated for the entire day. The March 22nd rain crust is 30-40 cm deep and is present to around 2000 m. The late February persistent weak layer is now down 40-100 cm below the surface. Both of these persistent weaknesses could wake up during warm and sunny weather. Loose wet slides or cornice falls could both act as triggers for deeper weaknesses.

Problems

Loose Wet

Watch for loose wet sluffing in steep sun-exposed terrain during the day.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Cornices could fail easily during the day when temperatures soar and the sun reappears.

Do your best to avoid traveling on or underneath cornices. If you have to, move quickly and only expose one person at a time.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Persistent Slabs

Intense solar radiation, a heavy wet surface sluff, or a cornice fall could be enough to trigger lurking deep weaknesses.

A few different buried persistent weak layers (PWL's) are lurking in our snowpack which means there is potential for large destructive avalanches that have the capability to run full path.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Apr 8th, 2016 2:00PM