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Avalanche Forecast

Archived

Apr 25th, 2019–Apr 26th, 2019

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

Regions

Purcells.

Lingering wind slabs may still be reactive to human triggers; especially on lee features below alpine ridgetops.

Confidence

Low - Due to the number of field observations

Weather Forecast

THURSDAY NIGHT: Increasing clouds / Light, southwesterly winds / Alpine low -4 C / Freezing level 1700 m.

FRIDAY: Mix of sun and cloud with isolated flurries; 0-3 cm. / Light, northwesterly winds / Alpine high 0 C / Freezing level 2000 m.

SATURDAY: Cloudy with flurries; 3-10 cm. / Light to moderate, westerly winds / Alpine high -5 C / Freezing level 1500 m.

SUNDAY: Sunny / Light, northeasterly winds / Alpine high -5 C / Freezing level 1500 m.

Avalanche Summary

No new avalanches were reported in this region on Wednesday. However, there are currently very few professional observers submitting daily observations. Please submit your observations to the MIN. Photos of avalanches or current conditions are particularly useful.

Last Saturday morning evidence of large (up to size 3) natural 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 up to 600 m away.

Snowpack Summary

A supportive surface crust caps a mostly isothermal snowpack at lower elevations. In the alpine, the recent snow is likely settling and preserved as cold, wintery, snow on north aspects where reactive wind slabs may still linger. A crust is present on all solar alpine aspects to mountain tops and below 2200 m on all aspects. The strength of the crust will depend on overnight freeze and the speed at which the snowpack warms up 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  or highly variable snowpack depth are the most likely places to trigger this layer.

Below treeline, snow is disappearing rapidly.

Problems

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.

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.