Avalanche Forecast Purcells

Date Issued: Valid Until:

Avalanche Canada dsaly, Avalanche Canada

Avalanche Forecast

Tue Apr. 23rd ยท 3:00PM

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 Low

Below Treeline

Danger Ratings Low

Wind slabs may react to human triggers around ridges and lee features. Loose wet avalanches remain a concern, especially on sunny slopes.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TUESDAY NIGHT: Cloudy with clear periods with isolated flurries, trace to 5 cm, light to moderate west wind, alpine temperature +2 C, freezing level 1300 m.

WEDNESDAY: Mix of sun and clouds, moderate northwest wind wind, alpine temperature +1 C, freezing level 1800 m.

THURSDAY: Cloudy with sunny periods, light west wind wind, alpine temperature -1 C, freezing level 2100 m.

FRIDAY: Mix of sun and clouds, light west wind, alpine temperature 0 C, freezing level 2200 m.

Avalanche Summary

On Saturday morning evidence of large (up to size 3) 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.

Avalanche activity 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. No avalanche observations were reported on Monday.

Snowpack Summary

Rain has soaked the snowpack at treeline and below. In the alpine, the recent snow is settling and preserved on north aspects. A crust is present on all solar alpine aspects and below 2200 m, the strength of which 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.
  • Be alert to conditions that change with elevation.

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

Elevations: Alpine.

Likelihood

Likely - Possible

Expected Size

1 - 2
Loose Wet

Loose Wet

Expect thin surface crusts to breakdown quickly during the day, especially on sunny slopes.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2