Avalanche Forecast

Issued: Mar 19th, 2015 9:04AM

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

swerner, Avalanche Canada

South Columbia.

Snow, rain and wind combined with buried weak layers is the perfect recipe for rising avalanche danger. The upper snowpack is complex, keep it simple and use a very conservative approach to terrain selection.

Summary

Confidence

Good

Weather Forecast

A series of pacific frontal systems will bring waves of precipitation to the Interior Ranges. Friday will see overcast skies, precipitation amounts 5-15 mm, ridgetop winds moderate from the SW and freezing levels 1800-2000 m. Continued precipitation on Saturday with amounts up to 15 mm , ridgetop winds light-moderate from the SW and freezing levels near 1900 m. Later Saturday the front will move east setting up for a clearer, drying trend Sunday. Freezing levels will initially drop to valley bottom overnight Saturday then rise steadily during the day with treeline temperatures near 0 degrees. The way this system is tracking, southern parts of this region will likely see less precip amounts then what's posted above.

Avalanche Summary

On Wednesday, several natural slab avalanches and skier triggered avalanches up to size 2 were reported. Most of these avalanches failed on north- easterly aspects above 2000 m. With forecast snow, rain and wind, widespread natural avalanche activity is expected through the weekend.

Snowpack Summary

At higher elevations, up to 20-50 cm of snow sits over a plethora of old surfaces including wind affected surfaces, and/or old wind slabs and crusts which were buried mid-March. Previous strong winds have redistributed new snow into wind slabs on leeward terrain features and lower elevations (below 2000 m) are sporting spring-like, melt-freeze conditions. Digging deeper (40-70 cm below the surface) sits the mid-February facet/ crust interface. This interface has not been as reactive in the South unlike regions to the North. However, it is alive and well in test profiles. It may just require additional load and/ or a change in slab properties before it reaches threshold and becomes reactive. The late-Jan crust/surface hoar layer (around 1m deep) and the mid-January surface hoar (around 1.5m deep) have been dormant for several weeks.

Problems

Storm Slabs

Touchy storm slabs continue to build and sit over a weakness from mid-February. These will likely be reactive naturally through the weekend. Overhead hazards like cornices are weak and could trigger slabs from slopes below.

Recent storm snow has been redistributed, and has loaded lee slopes, terrain features and convexities.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Loose Wet

Steady rain and warming at lower elevations will saturate and weaken the snowpack. Loose wet avalanches are likely.

Watch for clues, like natural avalanche activity, sluffing off of cliffs, and snowballing that the snowpack deteriorating. >Avoid exposure to terrain traps where the consequences of a smaller, wet and heavy avalanches could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Mar 20th, 2015 2:00PM