Avalanche Forecast

Issued: Mar 14th, 2017 4:07PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

mgrist, Avalanche Canada

South Columbia.

Rapid loading and warm temperatures are a recipe for HIGH danger. Conservative terrain use at all elevations is essential this week. Avoid overhead hazard and choose simple terrain!

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Warm temperatures and high freezing levels continue with moderate winds and heavy snow at times on Wednesday and Thursday.WEDNESDAY: Another 15-30cm of fresh snow (above 1700m), accompanied by moderate south winds. Freezing levels near 1900m. THURSDAY: More snow (10-20cm) accompanied by moderate southwest winds. Freezing levels dropping to 1400m. FRIDAY: Cloudy with isolated flurries (5cm) with moderate southwest winds. Freezing levels near 1300m.

Avalanche Summary

On Monday and Tuesday a widespread storm slab natural avalanche cycle to Size 2.5 was reported on a range of elevations and aspects. Wet slabs and loose wet avalanches were also reported below treeline. On Sunday, several large avalanches (up to Size 4) were reported with artillery control in Glacier National Park, some running full path to valley floor.On Sunday several small natural storm slab avalanches were reported near Revelstoke below treeline. Use extra caution for the time being in what is normally a 'safer' elevation band. See here for the excellent and informative MIN post.

Snowpack Summary

Around 50-80cm of fresh snow has fallen over the past several days (with light to moderate southerly winds). Touchy storm slabs can be found at all elevations with weaknesses within and under this recent snow.Warming temperatures on Sunday into Monday has resulted in moist (read: heavy) surface snow up to 2100m in most areas, and unstable wet snow below treeline.All this new snow is bonding slowly to faceted snow as well as isolated small surface hoar in sheltered areas and a thin sun crust on steep southerly aspects.The persistent weakness buried late-February is now down 80-140 cm, and is composed of a thick rain crust as high as about 1800 m, sun crusts on steep southerly aspects, and spotty surface hoar on shaded aspects. Recent reports show the bond to this interface slowly improving.The mid and lower snowpack are well settled and stable in deeper snowpack areas, but may be weak and faceted in shallow areas.

Problems

Storm Slabs

Weaknesses within the recent storm snow are susceptible to human triggering. These storm slabs are particularly deep and touchy on slopes loaded by southerly winds and have the potential to step down to deeper persistent weaknesses.

Minimize overhead exposure during periods of heavy loading from new snow, wind.The new snow will require several days to settle and stabilize.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Various persistent weaknesses strewn throughout the snowpack create the potential for large step-down avalanches. Warming is expected to increase the likelihood of these large avalanches, especially with cornice-fall triggers.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of the potential for wide propagations.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Mar 15th, 2017 2:00PM