Avalanche Forecast

Issued: Mar 12th, 2013 10:47AM

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

Cariboos.

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 West-Southwest winds overnight and during the day. Freezing level rising to 1600 metres.Thursday:Continued moderate to heavy precipitation and strong Southwest winds. Freezing level at 1600 metres.Friday: The precipitation is expected to taper off as the Westerly flow weakens.

Avalanche Summary

Some thin wind slab avalanches were reported from Monday. I suspect that poor visibility and travel conditions will limit observations from Tuesday.

Snowpack Summary

A new storm slab is developing due to strong Southwest winds, new snow, and warming temperatures. The new storm snow has buried a thin layer of new snow and wind transported snow that is covering a widespread layer of surface hoar that developed during the recent clear weather. Sun crusts also developed during the clear weather on solar aspects up to about 2000 metres. Some areas had strong winds before the surface hoar was buried, so the distribution may be specific to sheltered and shaded terrain features. There is still concern for the buried weak layer of surface hoar from February 12th that is now down more than a metre in most places. The forecast new load of snow and wind may overload this deeply buried weak layer in areas that did not slide after the last storm.

Problems

Storm Slabs

New snow and wind transported snow are expected to develop a new storm slab which may be above a weak layer of surface hoar and/or a sun crust. Warm temperatures and rapid loading may promote long fracture propagations resulting in large avalanches.

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

Likely

Expected Size

2 - 5

Persistent Slabs

A weak layer of surface hoar buried down about 100-150 cm (February 12th layer) may be triggered by the new load of storm snow or by avalanches in motion.

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

3 - 6

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