Avalanche Forecast

Issued: Feb 14th, 2017 4:20PM

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

jlammers, Avalanche Canada

South Rockies.

Wednesday's danger ratings are based on overcast skies. If the sun makes an appearance, consider the avalanche danger to be higher than posted.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Wednesday

Weather Forecast

Wednesday: Clear skies in the morning with increased cloud throughout the day / Strong southwest winds / Freezing level at 2500mThursday: 5-10cm of new snow / Strong southwest winds / Freezing level at 2100mFriday: Clearing skies / Light southwest winds / Freezing level at about 1800m

Avalanche Summary

Recent observations have been limited; however, a size 2 solar-triggered slab avalanche was observed at 2000m in the Elkford area on Tuesday. It was thought to be about a day old. For Wednesday, warm temperatures can be expected to promote instability within the snowpack. As the warm temperatures persist, and especially if we don't experience refreezing overnight, the potential for deep persistent slab releases will rise steadily each day. Any avalanches releasing on a basal weakness will likely be large and very destructive.

Snowpack Summary

Roughly 10 cm of new snow received late last week has been redistributed into wind slabs by strong southerly winds at upper elevations. Where it hasn't blown away, this new snow now lies above the 15-30 cm of dense snow that fell over the region on Thursday, which was mixed with periods of rain at lower elevations. Together, these more recent accumulations overlie the 90cm of low density storm snow that we received last weekend. Strong shifting winds redistributed this previous storm snow in exposed terrain, forming wind slabs over a variable old surface which includes wind affected surfaces, facets, and/or a rain crust below around 1500 m. The bond at the interface between this older storm snow and the previous surface is suspected to be improving slowly.In deeper areas, the snowpack appears to be well settled with only isolated concerns about the mid-December facet layer which was buried 50-100 cm deep prior to the weekend storm. In shallow snowpack areas and at lower elevations, the mid to lower snowpack is weak, faceted, and has no structure. In these areas the snowpack's weakness may reach a tipping point as warm temperatures persist over the coming days.

Problems

Deep Persistent Slabs

A weak layer at the bottom of the snowpack is creating the potential for full depth avalanche releases. This weakness has been stressed by recent snowfall and warming, and is more likely to fail in areas where there has been less rider compaction.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.The likelihood of deep persistent slab avalanches will increase with each day of warm weather.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Storm Slabs

Most of our upper snowpack is essentially a storm slab. Its bond to the underlying snow is improving, but continued warming may increase the likelihood of an avalanche. Watch for increased reactivity in high elevation wind-affected terrain.

Minimize exposure to sun exposed slopes when the solar radiation is strong.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

Warm temperatures will promote loose wet avalanches on Wednesday, especially in steep terrain. Use extra caution if the sun makes an appearance.

Use extra caution on solar slopes or if the snow is moist or wet.Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

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