Avalanche Forecast

Issued: Mar 16th, 2019 5:11PM

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

istorm, Avalanche Canada

Lizard-Flathead.

Warming is coming! This significant change will weaken the snowpack. Forecasting the timing of changes over the next several days is difficult. However, it's easy to see it's time to reign in your terrain choices and stay clear of overhead hazards.

Summary

Confidence

Moderate -

Weather Forecast

Significant warming in the forecast and next week looks very warm with freezing level above the summits. Don't let overnight cooling at low elevations fool you; very little cooling is expected at higher elevation.SATURDAY NIGHT: Clearing, alpine low temperature O to -5C, light southwest wind.SUNDAY: Sunny, with freezing level approaching 2200m, no overnight re-freeze expected. Light variable wind.MONDAY: Sunny with freezing level around 2500m, no overnight re-freeze expected. Light variable wind.TUESDAY: Sunny with freezing level around 2500m and alpine tempertures around +5C. Light variable wind.

Avalanche Summary

On Thursday, a group of riders remotely triggered a size 1.5 persistent slab from 100 metres away. See the MIN report for more details. I view this as an important piece of data when considering the effect of forecast strong sunshine and warming.Friday's reports were of wet loose avalanches to size 2 and skier triggered wind slabs to size 1.5 which is consistent with previous days trend. Explosives work was targetted on cornices and results were generally size 2 without any surprising results.

Snowpack Summary

The snow surface is getting moist on south and west slopes. Up to 40 cm of storm snow in the last week overlies various surfaces such as old and firm wind slabs in the alpine and open areas at treeline on all aspects. A widespread sun/ temperature crust is also found hidden under this new snow on south facing slopes. Isolated pockets of surface hoar crystals were observed at the surface on north-facing slopes around 2000m right before the last storm rolled in. The mid-snowpack consists of sugary faceted grains (facets) of different hardness. Two older layers of surface hoar still exist down 55-80 and down 95-150 around 1600-1900m. See Avalanche Activity section below for why this is relevant!

Problems

Storm Slabs

Sunshine and warming temperatures will peel away layers or recent snow on sunny slopes as loose wet slides, weaken cornices, and possibly re-energize wind slabs. The key unknown is how warming and weakening upper snowpack will affect deeper layers.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Minimize exposure to overhead hazards like cornices which could easily trigger persistent slabs.Parking, eating lunch, and regrouping in runout zones is bad practice.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A surface hoar layer formed in late January may be more reactive than expected, especially at lower elevations during periods of intense warming. See this MIN report for a recent remotely triggered avalanche attributed to sunshine and warming.

Be cautious in shallow snowpack areas where triggering a deeper layer is more likely.Warming could wake up buried weak layers.Remote triggering is a concern, watch out for adjacent slopes.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 2.5

Valid until: Mar 17th, 2019 2:00PM