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Avalanche Forecast

Archived

Feb 20th, 2014–Feb 21st, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Sea To Sky.

We'll soon be moving from a storm slab problem to a persistent slab problem. Check out this blog post for thoughts on the current situation and strategies for the next the chapter.

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

The bulk of the Pacific weather systems has moved through the area, but the forecast models disagree on whether there is any significant moisture in the forecast for the next 3 days.Thursday night:  Freezing level at valley bottom, light flurries possible, precipitation amount uncertain. Winds at ridge top gusting to 50 Km/h.Friday:  Freezing level at valley bottom, no precipitation in the forecast.  Cooler air moves into the region, ridge top winds up to 40Km/h.Saturday: Freezing level at valley bottom,  no precipitation in the forecast, ridge top winds from the north @ 25 Km/h.Sunday: Freezing level at valley bottom, no precipitation in the forecast, light ridge top winds.

Avalanche Summary

With all the new snow we've been getting, we're seeing reports of natural, skier triggered, and explosive control avalanches  up to size 2 throughout the forecast region. Most are storm slab avalanches and occurred around tree line and above. These appear to be running on the Feb. 10th facet/crust/surface hoar combination.

Snowpack Summary

Recent snowfall amounts exceed 1.75m during the past week and has now settled into a storm slab with a typical thickness of 60-100cm. The storm slab is overlying a variety of old weak surfaces that developed during the past cold, dry spell. It consists of weak facets, surface hoar, a scoured crust, wind pressed snow, or any combination of these. A poor bond exists between the storm slab and these old surfaces. Much of the recent storm snow has been redistributed into wind slabs on lee slopesOf particular concern is the combination of buried facets on a crust that has been reactive at tree line and below. Avalanche activity, whumpfing and snowpack tests at these elevations are showing easy sudden planar shear results on the facet/crust combo. Strong to extreme winds are redistributing the new snow into deeper, and denser wind slabs on lee slopes.The mid and lower snowpack are generally strong and well-settled. Basal facets and depth hoar are likely to exist in some parts of the region, but skier triggering has become unlikely.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.