Avalanche Forecast Purcells

Date Issued: Valid Until:

Avalanche Canada dsaly, Avalanche Canada

Avalanche Forecast

Mon Apr. 22nd ยท 4:21PM

Alpine

Danger Ratings Moderate

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Low
Wind Slabs Wind Slabs
Loose Wet Loose Wet

Alpine

Danger Ratings Moderate

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Low

Alpine

Danger Ratings Moderate

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Low

Travel early, a warming snowpack will increase the chance for loose wet avalanches through the day. Wind slabs may lurk in the alpine.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Mostly cloudy with isolated flurries, trace to 5 cm, light west wind with gusts to 60 km/h, alpine temperature +1 C, freezing level 2000 m.

TUESDAY: Cloudy with isolated flurries, light west wind with gusts to 50 km/h, alpine temperature +2 C, freezing level 2300 m.

WEDNESDAY: Mix of sun and clouds, light to moderate west wind wind, alpine temperature +1 C, freezing level 2300 m.

THURSDAY: Mix of sun and clouds, light west wind wind, alpine temperature -1 C, freezing level 2300 m.

Avalanche Summary

Evidence of an avalanche cycle continued through Sunday, natural wind slab avalanches to size 3 were observed with daytime warming and explosives triggered several size 2 wind slab avalanches on north and east aspects at 2500 m.

On Saturday morning evidence of large natural wind slab avalanche cycle was observed on all aspects above 1500 m; natural avalanches continued throughout the day, two large (2.5-3) natural wind slab avalanches were observed around 3 pm on south aspects. Storm and wind slab avalanches to size 3 were triggered with explosives on all aspects in the alpine (above 2300 m). Impressive results were recorded including sympathetic avalanches to size 2.5; one shot triggered 6 large avalanches as far as 600 m away.

On Friday, a natural wet slab avalanche cycle to size 3 was reported on all aspects from 2200-2700 in the western part of the forecast region. Toward the east, natural wet loose avalanches size 1.5-2.5 were seen on north-northeast aspects at 1900 m.

Snowpack Summary

The recent snow continues to settle in the alpine with cold snow prevailing on northerly alpine aspects and southwesterly winds developing slabs. A crust is present on all solar alpine aspects and below 2200 m, the strength/thickness of the crust will depend on overnight recovery and the speed at which the snowpack warms during the day.

Weak and sugary faceted grains may remain at the bottom of the snowpack in the alpine, producing a low likelihood but high consequence scenario. Steep, rocky areas with a shallow snowpack are the most likely places to trigger this layer. At lower elevations the snowpack is below threshold and the bike trails are quickly drying.

Problems

Wind Slabs

Wind Slabs

Over the weekend, large (up to size 3) storm/wind slab avalanches were observed in the alpine. Use caution around ridges and lee features, slabs may still be reactive to human triggers.

  • Be careful with wind-loaded pockets, especially near ridge crests.
  • Expect conditions to change rapidly with aspect and elevation.
  • Use small, representative slopes without consequence to test the bond of the recent snow.

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

Elevations: Alpine.

Likelihood

Likely - Possible

Expected Size

1 - 2
Loose Wet

Loose Wet

Overnight freezing levels around 2000 m will prevent strong crust recovery. Expect thin surfaces crusts to breakdown quickly during the day.

  • Use extra caution on slopes if the snow is moist or wet.
  • Avoid terrain traps such as cliffs and gullies that increase the consequence of small avalanches.
  • Minimize overhead exposure and avoid steep slopes during periods of strong sun.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Possible

Expected Size

1 - 2