Travel was Tricky below Treeline on Thursday - our skis repeatedly punched through wet old Storm Slab and crusts, into hollow feeling facets below. The snowpack structure remains less than ideal - dig deep and do snowpack tests.
Weather Forecast
Snowfall Thursday night (but rain below 1700m) tapers off Friday morning. Friday: Freezing Level 1500m, Clearing trend, Moderate - Strong Westerlies easing.Saturday: Cold initially, freezing level rises to 1700m. Light SE winds, snowfall beginning later.Sunday: Snowfall ending early, sky clearing for a time. Moderate S wind. Freezing level 1700m.
Snowpack Summary
Upto 12mm rain below 1800m Thursday, and more forecast. The upper snowpack is wet below 1800m. Storm slabs are forming up higher. A older, cohesive slab keeps producing Moderate, Sudden test results on a Persistent Weak Layer down 60-90cm (crust on sunny slopes, facets in sheltered areas from 1700-2150m, basal facets in shallow snowpack areas.)
Avalanche Summary
On Thursday, several small-large (Size 1 - size 2) avalanches were observed in steep paths Below Treeline. They were mainly Loose Wet, triggered by steady rainfall. One was a Deep Persistent Slab, releasing on ground in a thin snowpack area. Starting small, it gouged wet snow in its track, finishing large.
Confidence
Forecast snowfall amounts are uncertain
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.