Purcells Avalanche Forecast

Issued: Mar 30th, 2021 4:00PM

Wed Mar 31st Current Conditions
Alpine Considerable Treeline Moderate Below Treeline Moderate
Thu Apr 1st 2 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate
Fri Apr 2nd 3 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Low

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

Rising temperatures coupled with spring sun can pack a punch and quickly initiate natural avalanche activity and weaken cornices. Be ready to back off slopes as the surface becomes moist. Moderate wind could help keep things cool, but could also be building new wind slabs.

Summary

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Tuesday night: Mix of sun and cloud. Light to moderate northwest wind. Freezing level 500 m. Alpine temperature -7.

Wednesday: Sunny. Light to moderate southwest wind. Freezing level 2000 m. Alpine temperature -1.

Thursday: Mix of sun and cloud. Moderate southwest wind. Freezing level 2000 m. Alpine temperature -1.

Friday: Scattered flurries. Light to moderate southwest wind. Freezing level 1800 m. Alpine temperature -4.

Avalanche Summary

On Monday, numerous skier and explosive triggered storm slab avalanches were reported size 1-1.5, largely on NW aspects. By Tuesday, storm slabs became more stubborn to explosives and results were limited. Observations in the Hellroaring area, which received less snow, include a few size 1 wind slabs and a cornice-triggered size 1.5.

Reports during the storm on Sunday include several natural storm slabs size 1-2 and a natural size 2 loose wet avalanche on a northeast aspect around 1700 m. It is suspected to have scrubbed down to a crust near the ground, as rain and warm temperatures destabilized the full depth of the snowpack. Keep this one in mind as the snowpack heats up again on Wednesday.

Snowpack Summary

15-40 cm of recent snow has seen some redistribution by southwest to northwest wind, and seems to be bonding well with underlying surfaces. Dry snow that sees direct sun or experiences above freezing temperatures for the first time Wednesday may become reactive as it settles rapidly. Crusty surfaces below treeline will become moist with rising freezing levels.

A widespread crust layer from the mid-March warm spell can be found 30-60 cm deep, and small surface hoar has been observed at this depth on some isolated north-facing slopes. Reports suggest the snow is generally well bonded to these layers. Deeper layers are strong and have been unreactive over the past few weeks. 

Terrain and Travel

  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • Remember that in the spring strong solar radiation and warm temperatures can weaken the snow in a matter of minutes.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Storm slabs are most likely to be reactive:

- at elevations with dry snow experiencing rapid warming for the first time (around 1800 m)

- on dry southerly aspects seeing strong sun for the first time

- in freshly wind loaded terrain features at upper elevations

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Cornices

An icon showing Cornices

Likelihood

Possible-Likely

Expected Size

2 - 3

Cornices are fragile due to rapid growth from recent snow and wind. Strong sun will further weaken them. Cornice falls are dangerous in their own right and they can also trigger slabs on slopes below.

Aspects:

North, North East, East.

Elevations:

Alpine.

Loose Wet

An icon showing Loose Wet

Likelihood

Likely

Expected Size

1 - 1.5

Wet loose avalanches are possibly below treeline.

Dry loose avalanches will be very likely on steep south facing slopes at upper elevations when the sun comes out in the afternoon.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Mar 31st, 2021 4:00PM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.