Avalanche Forecast

Archived

Feb 18th, 2020–Feb 19th, 2020

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Sea To Sky.

As you travel, be observant for moistening snow on sun-exposed slopes and for lingering wind slabs.

Confidence

High - Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

TUESDAY NIGHT: Clear skies, light northeast wind, alpine temperature -4 C, freezing level 500 m.

WEDNESDAY: Clear skies, light south wind, alpine temperature -2 C, freezing level 1500 m.

THURSDAY: Clear skies, light to moderate southwest wind, alpine temperature -4 C, freezing level 1300 m.

FRIDAY: Increasing clouds, moderate southwest wind, alpine temperature -5 C, freezing level 1000 m.

Avalanche Summary

Small wind slabs and wet loose avalanches were triggered naturally and by humans on Monday. The wind slabs generally occurred on northerly aspects and the wet loose avalanches on southerly aspects.

With clearing skies gave views of the surrounding mountains. Numerous people reported slab avalanches in the Spearhead Range. The avalanches were far away but could have released on the basal instability described in the Snowpack Summary.

Snowpack Summary

Clear skies have formed a melt-freeze crust on sun-exposed aspects, which will moisten during daytime heating. Soft snow should prevail on shaded aspects, which overlies hard surfaces and potentially surface hoar in sheltered terrain around treeline. Isolated wind slabs may still linger in steep, lee terrain features in the alpine.

The midpack is well-settled. Faceted snow and crusts exist near the base of the snowpack in much of the region. Avalanche activity was recently noted on Curtain Glacier in the Spearhead Range, although it is unclear if the avalanches released on this basal instability. This layer is largely dormant at the moment but appears to be most likely a problem on the eastern side of the region, in alpine terrain, and where there is relatively smooth ground (e.g., glaciers, scree slopes, rock slabs).

Terrain and Travel

Carefully evaluate steep lines for wind slabs.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.