Strong winds and new snow will be driving the avalanche danger to HIGH. If you see more than 30cm of new snow, avoid all avalanche terrain, free from overhead hazard.
Confidence
Low - Intensity of incoming weather systems is uncertain on Tuesday
Weather Forecast
Snow and strong winds on Tuesday; clearing up Wednesday into Thursday. TUESDAY: Snow (20-30cm). Moderate to strong south / west winds 30-70 Km/hr. Freezing level rising to 1600 metres with alpine high temperatures around -5. WEDNESDAY: Sunny with cloudy breaks and isolated convective flurries. Moderate northwest winds 20-45 Km/hr. Freezing level to 1400 metres with alpine high temperatures around -7.THURSDAY: Cloudy with flurries bringing up to 5-10 cm of new snow, increasing overnight. Moderate southwest winds 20-40 Km/hr. Freezing level 1400 metres with alpine high temperatures of -5.
Avalanche Summary
On Monday, backcountry skiers triggered a size 2 wind slab on a northeast aspect near 2050m. The slab's thickness varied from 40-60cm. On Saturday we received reports of several wind slabs and storm slabs to size 2.5, mostly on northerly aspects above 2200m. Also on Saturday, a wet loose size 1.5 avalanche injured a skier in Glacier National Park on a west aspect near 2000m.
Snowpack Summary
New snow fall amounts into Monday range from 5-11 cm. Winds have been moderate south/east, creating fresh wind slabs on down wind (lee) slopes. Wind slabs from late last week (thanks to south / east winds) remained reactive throughout the weekend on immediate lee features. Isolated pockets of surface hoar (buried March 18th) have been reported between old storm snow layers on shaded aspects at higher elevations and may be found approximately 25-40 cm below the surface. New snow amounts taper with elevation and below 1800 m, reduced accumulations have buried a supportive crust on all aspects. Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with a surface avalanche stepping down, large cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets.
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.