Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Mar 4th, 2021–Mar 5th, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells.

Warm temperatures and sunshine will elevate avalanche conditions across the region. Conditions in the northern end of the region (e.g. Quartz Creek and Dogtooth Range) are most concerning given recent avalanche activity. Stick to low angle shaded terrain.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Temperatures gradually cool as the ridge of high pressure breaks down.

THURSDAY NIGHT: Clear skies, moderate southwest wind, a weak temperature inversion may develop overnight with alpine temperatures in the -2 to 0 C range and cooler in the valleys.

FRIDAY: Mostly sunny with some afternoon clouds, moderate south wind, freezing level around 2100 m with treeline temperatures near 0 C.

SATURDAY: Cloudy with scattered flurries and up to 5 cm of new snow, light southwest wind, freezing level climbs to 1700 m with treeline temperatures around -3 C.

SUNDAY: Mix of sun and cloud with isolated flurries, light wind, freezing level around 1300 m with treeline temperatures near -5 C.

Avalanche Summary

Preliminary reports from Thursday suggest there were some wet loose avalanches on sun-exposed slopes. On Friday the primary concern is natural avalanches on steep sun-exposed slopes. These will most likely present as wet loose avalanches, but larger wind and persistent slab avalanches are also possible. Read the latest Forecaster Blog for concerns about the warming.

Over the past week there have been several notable reports of large human triggered persistent slab avalanches in the Dogtooth Range and Quartz Creek area. This includes a remotely triggered size 2 avalanche on Tuesday on a northwest slope at 2100 m that failed on a 40 cm deep weak layer (MIN report), a size 3 human-triggered avalanche on Feb 27 on a east-facing alpine slope (MIN report), a size 2 avalanche on Feb 27 on a south-facing slope (MIN report), and a few remotely triggered size 2 avalanches on Feb 24 (MIN report).

Snowpack Summary

Rising freezing levels and sunshine will be melting, and potentially destabilizing, snow surfaces the next few days. Higher elevations have been impacted by recent wind from the southwest, likely leaving wind slabs lurking on shaded north and east slopes.

Persistent weak layers have been most active in the northern end of the Purcells where a buried layer of surface hoar that formed in late January is 40-80 cm deep and an older surface hoar layer is 60-120 cm deep at treeline. These layers may exist as a combination of facets and crusts at other elevations. Recent observations suggest these layers have been less problematic as you move further south.

Steep rocky areas where the snowpack is thin likely has addition weak layers near the base of the snowpack.

Terrain and Travel

  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Choose gentle slopes without steep terrain above.
  • Caution around convexities or sharp changes in terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.