Ratings are based on the region staying mostly dry on Tuesday morning. If you do see significant snowfall (20+ cm) by noon on Tuesday, consider ratings to be High / Considerable / Considerable.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Synopsis: Northwesterly flow will bring a series of moderate or locally heavy pulses of precipitation to the region through the forecast period.Tuesday: Should stay cold (-12C) and dry for the first half of the day. Moderate or locally heavy precipitation beginning in the afternoon, with 10-20 cm expected by Wednesday morning. The heaviest snowfall is likely to be found to the north and east of the region. Treeline temperatures rising to around -8C. Northwesterly winds, gusting to 60km/h at ridgetop during the afternoon.Wednesday: Further light snowfall, around 5 cm. Treeline temperatures peaking around -2C. Strong northwesterly winds gusting to 50km/h at ridgetop.Thursday: Dry, cold (-12C) with generally light northwesterly winds.
Avalanche Summary
No new avalanches were reported through the weekend. On Friday, a couple of small (size 1) avalanches were triggered on convex rolls by ski cutting on south aspect slopes.
Snowpack Summary
Around 40-50 cm recent new snow has settled into a 20-30 cm soft slab overlying a weak layer comprising of facets at higher elevations, surface hoar on shady slopes, and a sun crust on solar aspects. The recent new snow sitting above this interface has been slowly consolidating from fresh powder into a more cohesive slab. As this process continues, the avalanche character will change from relatively harmless loose sluffs to more dangerous slab avalanches. However, note this upper weak layer has been reported to be patchy and variable in distribution. A mid-pack layer buried in early January surface hoar layer is down 70-90 cm. While this layer is still on the radar of professional observers, with most likely trigger points being on steep rolls below 1600 m, there has only been one small avalanche (size 1 at 1200 m on a north aspect) reported on this layer from the region for approximately 10 days.
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.