Confidence
Fair - Freezing levels are uncertain on Tuesday
Weather Forecast
Synopsis: Northwesterly flow will bring a series of low-intensity pulses of precipitation interspersed with short-lived periods of clear weather to the region through the forecast period. Temperatures will start out fairly cool but rise through Tuesday and into Wednesday to become mild.Monday: Flurries. Treeline temperatures around -7C. Light westerly winds.Monday night: Light snowfall, up to 5cm.Tuesday: Mainly dry during the day. Temperatures rising to a high of -3C at treeline elevations. Northwesterly winds, gusting to 30km/h at ridgetop.Wednesday: Light snowfall, up to 5cm. Treeline temperatures around -1C. Northwesterly winds gusting to 40km/h at ridgetop.
Avalanche Summary
Only two small avalanches (N and NE aspects) associated with explosive control were reported on Saturday, and none were reported Sunday. On Thursday and Friday, a small avalanche cycle produced avalanches up to size 1.5 running on the recently buried upper surface hoar layer.
Snowpack Summary
Recent storm snow amounts over the past few days are 30 to 40 cm with as much as 60cm reported. On Friday this snow remained mostly loose and powdery except for pockets of windslab behind ridges and ribs. Over the weekend, this storm snow started to settle into more of a cohesive slab, although little activity was reported through the weekend. Below the new snow is a suncrust on steep southerly facing slopes and a surface hoar layer at treeline and lower elevations (but it has a patchy distribution). Early January surface hoar is now around 60 - 80 cm deep and is also patchy and most likely to be preserved in shady slopes below treeline. Note, however, it may extend into the alpine in places.
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.