Natural avalanches possible, human triggered probable.
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 unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
North Columbia.
The intensity of the warming this weekend is uncertain. This uncertainty is best handled with cautious route selection.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
FRIDAY NIGHT: Partly cloudy, temperature inversion from 1700 m to 2500 m with 0C in the alpine. SATURDAY: Mix of sun and cloud. Temperature inversion from 1600 m to 2800 m with +2C in the alpine.SUNDAY: Mix of sun and cloud. Temperature inversion from 1700 m to 2700 m with +2C in the alpine. MONDAY: Sunny with cloudy periods. Temperature inversion from 1700 m to 2500 m with up to +4C in the alpine.
Avalanche Summary
On Thursday, several size 1-2.5 natural and human triggered avalanches were observed in steep slopes at treeline and in the alpine on all aspects. With the expected warming on the weekend there is a possibility of triggering deeper layers in the snowpack, see the MIN post here as an example.
Snowpack Summary
Warm upper-level air temperatures may be impacting the snow surface. You may find dry snow, moist snow, or possibly a frozen melt-freeze crust, depending on how warm the air temperatures are. The warm air may produce touchy storm slabs at all elevations. At the highest of elevations, wind slabs may still linger in lee and cross-loaded terrain features.The middle and lower portions of the snowpack are generally well-settled and strong. However, there still remain a few deeper weaknesses in the snowpack around treeline and alpine elevations. Professionals are still tracking a layer around 150 to 200 cm deep, composed of sugary faceted grains, feathery surface hoar, and a sun crust. The base of the snowpack may also still be composed of weak faceted grains. The likelihood of triggering these layers may increase with the warm air incoming this weekend. These layers would most likely be triggered by humans in areas where the snowpack is shallow.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.