Avalanche Forecast
Issued: Dec 14th, 2019 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ghelgeson,
Avalanche Canada
Improving visibility beckons us into the alpine, but we need to watch for fresh slab formation as northwest wind picks up Sunday. At and below treeline, 20 to 30 cm of storm snow rests on surface hoar which teeters on the brink of becoming a touchy storm slab problem.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
We’re entering a rather quiet period with no significant snow expected until Monday afternoon. The next 48 hours are marked by seasonally normal temps, potentially sunny periods and a bit of northwest wind at ridgetop.
SATURDAY NIGHT: Freezing level at valley bottom, moderate northwest wind largely confined to the high peaks, no significant precipitation expected.
SUNDAY: Broken cloud cover, freezing level at valley bottom, light west/northwest wind at most elevations with moderate to strong northwest wind at ridgetop, no significant precipitation expected.
MONDAY: Broken cloud cover, freezing level at valley bottom, moderate west/southwest wind, snow beginning late in the day, potential for 5 to 15 cm by Tuesday morning.
TUESDAY: Overcast, freezing level beginning at valley bottom rising to 1400 m by sundown, strong southerly wind, 2 to 10 cm expected during the day, 5 to 15 more cm possible Tuesday night.
Avalanche Summary
No new avalanche activity to report from Friday.
Reports from Thursday included sloughing and loose dry size 1 avalanches in the storm snow, as well as a persistent slab avalanche triggered remotely by a helicopter. It is important to keep in mind the potential for large, persistent slab avalanches.
Snowpack Summary
A total depth of 150-300 cm of snow sits in the alpine in central parts of the region. 15-30 cm of new snow has covered a layer of feathery surface hoar crystals that were observed at all elevations throughout the region. The new snow can be expected to gain cohesion and settle into a slab in the mild temperatures, especially at treeline and below.
The primary layers of concern at this time are a couple of weak layers in the mid snowpack, formed in late November and early December which can be found most notably at treeline, and may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect. These types of weak layers are typical failure planes, on which overlying slabs can start to slide and produce avalanches.
Problems
Storm Slabs
20 to 30 cm of recent storm snow rests on a widespread layer of large surface hoar. The storm snow is teetering on the edge of becoming a potentially touchy slab problem, but it hasn't happened yet. Northwest wind Sunday is likely to form fresh sensitive wind fueled storm slabs in wind exposed features, especially steep pieces of terrain near ridge crest.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A couple of weak layers formed in late November and early December are now sitting about 1 m below the surface. This layer may present as surface hoar, a crust, facets or a combination of those, depending on elevation and aspect. They can most likely be found in areas sheltered from the wind, but open to a view of the sky, such as near treeline.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 15th, 2019 3:00PM
