Avalanche Forecast

Issued: Mar 21st, 2019 4:51PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Persistent Slabs and Loose Wet.

jsmith, Avalanche Canada

Northwest Inland.

Avoid steep, rocky terrain in the alpine where there is a shallow or highly variable snowpack depth. This will reduce the likelihood of triggering large persistent slab avalanches.

Summary

Confidence

High -

Weather Forecast

THURSDAY NIGHT: Increasing cloudiness / Light to moderate, southwesterly winds / Alpine low 5 C / Freezing level 2400 m.FRIDAY: Mostly cloudy / Moderate, southeasterly winds / Alpine high 5 C / Freezing level 2400 m.SATURDAY: Snow/rain; 5-10 mm precipitation / Moderate, southwesterly winds / Alpine high -1 C / Freezing level 1500 m.SUNDAY: Mix of sun and cloud / Light, easterly winds / Alpine high -1 C / Freezing level 1600 m.

Avalanche Summary

The natural avalanche activity has been slowing down a bit. However, as of Wednesday afternoon, naturally triggered loose wet avalanches up to 2.5 on sun-exposed aspects continue to be reported.Reports from Monday included an observation of a size 3 (very large) persistent slab running full path and within 100 metres of the viewing platform at Twin Falls. This highlights the current elevated danger in lower elevation areas threatened by large overhead avalanche paths. Please see the Northwest Coastal forecast's avalanche summary for a description of the natural avalanche cycle that is ongoing in this neighboring region. With limited observations inland, it is advised to treat this activity as an indication of potential similarities to this region.Looking forward, expect heightened avalanche activity to continue and potentially expand to all aspects, so long as temperatures remain elevated and overnight freezing of the snow surface remains weak.

Snowpack Summary

Up to 50 cm of settled snow from storms last week sits on the surface. With the help of warm temperatures, the 50 cm of snow from last week's storm has either settled into a slab on shaded aspects or becomes increasingly isothermal (slushy) on sun-exposed aspects. Where it exists as a slab, it overlies weak facets (sugary snow). The prolonged period of cold temperatures in February had an overall effect of weakening the upper and mid-snowpack, as well as the basal (lower) snowpack in shallow areas. These weaknesses are increasingly being tested under the pattern of strong warming currently affecting the region.

Problems

Persistent Slabs

Old weaknesses may reactivate under sustained sunshine and warming. There are numerous reports of large slab avalanches in the neighboring Northwest Coastal region, some of them remotely triggered. Expect similar potential in the Northwest Inland.

Loose wet avalanches may initiate slab releases that result in even larger avalanches.Avoid steep, rocky terrain in the alpine where there is a shallow or highly variable snowpack depth

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 3

Loose Wet

Sunshine and warming will destabilize surface snow - especially on steep, sunny slopes. This problem may expand to include shaded aspects under sustained warming. Large loose wet avalanches can impact lower elevations with destructive debris flows.

Avoid exposure to steep, sun exposed slopes when the solar radiation is strong.Be aware of overhead hazards and avoid exposure to avalanche runout zones.Be aware of loose wet avalanche problems expanding to shaded aspects as warm temperatures persist.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Mar 22nd, 2019 2:00PM