Avalanche Forecast

Issued: Mar 12th, 2013 10:37AM

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

triley, Avalanche Canada

South Columbia.

Warm, wet, and windy! The storm will cause High avalanche danger for the next few days.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

Overnight and Wednesday: A strong Westerly flow will continue to bring moderate to heavy precipitation and strong Westerly winds overnight and during the day. Freezing level rising to 1900 metres.Thursday: Continued moderate to heavy precipitation and strong Westerly winds. Freezing level at 1700 metres.Friday: The precipitation is expected to taper off as the Westerly flow weakens.

Avalanche Summary

Some thin new wind slab releases were reported from Monday. Preliminary reports from some areas on Tuesday say that the new storm slab is very reactive, with widespread remote triggering and long propagations across terrain feature boundaries. There have been no reports of observations from the alpine due to poor visibility and travel conditions. The storm continues to develop and avalanche size and frequency is expected to increase.

Snowpack Summary

A warm and wet new storm slab is developing above a new surface hoar layer on shaded aspects and a sun crust on solar aspects. The new storm slab was reported to be very reactive today with avalanches up to size 1.5 triggered from remote locations and propagating long distances. The weak layer of surface hoar that was buried on February 12th is now down about 100-150 cm and was not triggered by cornice falls over the weekend. Some areas report that the February 12th surface hoar is rounding and getting harder to shear in snow profile tests, but continues to give planar shears when it does fail. The new load of storm snow may cause another cycle of natural activity on the February 12th weak layer.

Problems

Storm Slabs

The new storm slab continues to develop, and is very easy to trigger. Natural avalanches will continue to release and are expected to increase in size overnight.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 6

Persistent Slabs

A weak layer of buried surface hoar down about 100-150 cm may be triggered by the load of new storm snow and wind.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

4 - 7

Valid until: Mar 13th, 2013 2:00PM