Forecast Archive Avalanche Canada Cariboos This is archived for a fatality on Feb 23. The location was slightly outside the official forecast areas but was very close to three different zones. The Cariboos forecast (this one) and Northern Columbia were almost the same. The Northern Rockies was a few days old but had this information plus some other factors for that region which do not appear to apply. Date Issued: Monday, February 22, 2021, 04:00 Valid Until Tuesday, February 23, 2021, 04:00 Prepared by ahanna This is an archived avalanche bulletin. Heavy overnight snowfall and cranking wind are a recipe for HIGH avalanche danger. Minimize your exposure to avalanche terrain Monday. Danger ratings Tuesday Alpine: 3 - Considerable Treeline: 3 - Considerable Below Treeline: 3 - Considerable Travel and Terrain Advice Use increased caution at all elevations. Storm snow is forming touchy slabs. Storm slabs in motion may step down to deeper layers resulting in large avalanches. Stick to simple terrain features and be certain your location isn't threatened by overhead hazard. Avalanche Problem 1: Storm Slab All elevations and aspects Certain Small to Large 30-100 cm of recent storm snow continues to accumulate and settle into a slab in the mild temperatures. This storm slab sits overtop a thick layer of weak, sugary facets. At upper elevations, the recent snow will be easily blown around by strong to extreme westerly winds, forming thick, reactive slabs in lee features. Avalanche Problem 2: Persistent Slab All elevations and aspects Unlikely to Possible Large to Very Large A persistent weak layer buried 70 to 120 cm deep is being tested by these significant new snow loads. We are awaiting reports of avalanche activity during the storm, specifically whether they include evidence of step- downs, to determine whether or not this layer continues to be a problem. Avalanche Summary A size 1.5 loose dry avalanche was reported Friday out of steep rocky terrain near Valemount. With mind temperatures and cranking overnight winds, increased storm slab activity is expected at all elevations Monday. Last week, older winds slabs in cross and reverse-loaded terrain features surprised a number of skiers, triggering avalanches up to size 2.5. This surprisingly large human triggered avalanche was reported on a northwest facing feature at treeline. Snowpack Summary 10-25 cm of new snow is forecast to fall overnight. Recent snowfall amounts have been highest in the south of the region near Blue River, where current storm totals are in excess of 100 cm as of Sunday morning! Other areas have received as little as 20 cm since the cold snap. At upper elevations, all of this recent snow will be easily blown around by strong to extreme westerly winds, forming thick, reactive slabs in lee features. At lower elevations, this recent low density snow is likely settling and gaining slab property in the warm temperatures. Below sits the old, facetted and/or extensively wind affected snow that sat on the surface during the extended cold, windy drought period. There is uncertainty around the strength of this interface with the new snow, which will surely be tested by the ongoing loading. We've now got 80 to 180 cm of snow above the early February persistent weak layer which is composed of surface hoar. This layer is most prevalent at treeline and in "treeline-like" features like cutblocks. On steep south-facing terrain, this layer may consist of facets on a sun crust. Weather Summary SUNDAY NIGHT: 10-25 cm of new snow, strong to extreme westerly wind, freezing level 1500 m. MONDAY: Around 5 cm of new snow, moderate to strong westerly ridgetop wind, freezing level 1300 m. TUESDAY: Mix of sun and cloud, moderate westerly wind, freezing level 800 m. Confidence: High We are confident a natural avalanche cycle will begin shortly after the arrival of the incoming weather.