Avalanche Forecast
Issued: Mar 3rd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Cornices and Loose Wet.
swerner,
Avalanche Canada
This is the first significant warm-up in March and we expect this to complicate current avalanche conditions. The danger may be CONDSIDERABLE in the morning but on the rise for the afternoon. Check out the new Forecaster Blog on warming and the effects on our complex snowpack
Summary
Confidence
Weather Forecast
It's a hot and sunny forecast with generally light to moderate south wind. Thursday through Saturday will see mostly sunny skies with patches of cloud cover. Freezing levels are forecast to rise above 2000 m driving alpine temperatures above freezing. Sunday should bring cloud cover and a cooling trend.
Avalanche Summary
No recent avalanche reports on Wednesday.
Sun and warming is our primary concern over the next few days. Large looming cornices may weaken and fail, triggering slabs on the slopes below. Loose-wet avalanches will likely be seen from solar aspects first and then possibly all aspects. The persistent slab sitting above weak layers may stiffen and consolidate further, failing as a natural avalanche or becoming more sensitive to skier and rider triggers.
Pockets of wind slab may be reactive on northeast-east aspects at upper elavtions.
Snowpack Summary
Large, looming cornices exist on many ridgelines and threaten slopes below. Strong west-southwest winds have formed wind slabs on leeward slopes while freezing rain formed a widespread breakable crust 1-5 mm below 1800 m and in spotty locations at upper elevations.
Up to 50 cm of snow sits above a variety of old interfaces that formed mid-February and 60-100 cm down is a persistent weak layer that was buried in late January. These mostly include sugary facets, hard wind pressed surfaces, surface hoar in wind-sheltered locations, and sun crust on steep solar aspects. The South Rockies Field Team was near the powder cowboy sled zone today and their snowpack tests showed easy results (CTE 7 SC down 60) on a persistent weak layer.
There are no deeper layers of concern.
Terrain and Travel
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Problems
Persistent Slabs
Two layers of concern exist and have been reactive over the past couple of days. The upper layer being buried mid-February down 30-50 cm and has recently failed primarily on a sugary facet interface and the deeper layer of concern is found down 60-100 cm. This layer consists of surface hoar, faceted grains, and/or a melt-freeze crust. The layer has been most problematic around treeline elevations and in openings below treeline, but also reaches into the lower alpine.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Large looming cornices exist along ridgelines and require a wide berth from above and below. The likelihood of them becoming weak and failing is greater with warming and solar radiation. They have the potential to trigger slab avalanches from slopes below.
West to southwest wind has formed pockets of wind slab on leeward slopes. These could be triggered by the weight of a skier or rider, especially on east-northeast aspects.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Wet loose avalanches are likely when the sun pokes out and freezing levels rise. Be observant as you travel, and look for signs of warming and snowpack instability. Snowballing, moist snow, and the most obvious is natural avalanche activity. Back off slopes and adjust your trip plan when things are heating up.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 4th, 2021 4:00PM
