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 13th, 2021–Mar 14th, 2021

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

Regions

Lizard-Flathead.

We are expecting another hot day and temperatures will stay above freezing in the alpine overnight. The warmth will weaken cornices and may increase the reactivity of the persistent weak layers. Conditions may change rapidly with daytime heating and sun exposure.

Confidence

Moderate - Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather. Uncertainty is due to the fact that cornice falls are particularly difficult to forecast.

Weather Forecast

SATURDAY NIGHT: Clear, 30 km/h south wind, alpine low +1 C, above freezing layer between 1500 and 2700 m.

SUNDAY: Sunny, 20 km/h southwest wind, alpine high +7 C, freezing level 2500 m.

MONDAY: Mostly sunny, 20 km/h northeast wind, alpine high +6 C, freezing level 2300 m.

TUESDAY: Mix of sun and cloud, 15 km/h northeast wind, alpine high +5 C, freezing level 2200 m.

Avalanche Summary

A couple natural slab avalanches of size 2 were observed on sun-exposed slopes on Saturday as well as numerous small wet loose avalanches up to size 1.5 on steep solar features in the alpine. A few small avalanches were reported on east aspects on Friday. A few small loose and slab avalanches were triggered on sun-exposed slopes in the alpine during the heat of the day on Wednesday.

Snowpack Summary

A thick melt-freeze crust is present in many areas, with the exception being on north aspects above around 1700 m. Wind slabs may still exist on northerly aspects at alpine and treeline elevations. On solar aspects and below the freezing level, the snow will moisten during the heat of the day. Cornices will also weaken over the day.

Around 30 to 50 cm of snow overlies a variety of old interfaces that formed in mid-February. There hasn't been recent avalanche activity on this layer, but it remains possible to be triggered where it exists. The more active layer was buried late January, which is found 50 to 100 cm deep. This layer is mostly composed of sugary faceted grains, hard wind pressed snow, feathery surface hoar in wind-sheltered locations, and a melt-freeze crust on steep solar aspects. Periodic avalanches continue to be triggered on this layer. Check out this MIN for a photo of the positioning of these layers in the snowpack.

Terrain and Travel

  • Cornices become weak with daytime heating or solar exposure.
  • Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Be alert to conditions that change throughout the day.

Problems

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.

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.