Avalanche Forecast
Regions: North Columbia.
Watch for fresh slabs Wednesday from overnight winds and flurries. Seek out sheltered terrain - the most reactive deposits will be in exposed terrain around ridges and unsupported slopes. In alpine terrain where less than 15 cm snow accumulates hazard may be Moderate.
Confidence
Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.
Weather Forecast
TUESDAY NIGHT: Cloudy and unsettled with flurries, 10-20 cm overnight. Moderate southwest wind, alpine low -10C, and freezing level hovering around 1000m.
WEDNESDAY: Snow, 5-15 cm falling through the day, accumulating 20-35 by the end of the day. Moderate southwest wind decreasing though the day, alpine high -2C, and rising above 1500 m by days end.
THURSDAY: Unsettled with flurries and sunny breaks, 5 cm. Light west wind, alpine high +1C, and freezing level rising to 1500 m.
FRIDAY: Unsettled with isolated flurries, trace to 5 cm. Moderate west wind, alpine high -1C, and freezing level beginning near valley bottom rising to 1600 m.
Avalanche Summary
On Monday, explosives triggered several size 1-1.5 avalanches on NW-N-NE aspects above 1800 m. Small dry-loose avalanches were reactive to skiers in steep terrain. And several natural storm slab avalanches size 2-2.5 were reported in Glacier NP, occurring on north-northwesterly aspects above 1950m.
On Sunday, explosives and skier traffic triggered numerous size 1 avalanches. A few small dry loose avalanches and sluffing in steep terrain was also reported.
On Saturday in Glacier NP, a handful of storm slabs size 1.5-2.5 released naturally from steep north-northwest aspects above 2000 m. A large (size 2.5) glide crack release from a west aspect.
On Friday, several glide slab avalanches (size 2-3) were observed on south and east aspects around the TCH highway corridor. Loose wet avalanches to size 2.5 were reported around the region; a natural loose-wet cycle was reported around Rogers Pass initiating with evening rainfall.
Snowpack Summary
Southwesterly winds and flurries will form fresh slabs in lee features. 20-35 cm (up to 60 cm in areas) recent snow covers dry and compacted snow on polar surfaces above 1800 m and crusts on solar slopes; storm snow has been sluffing easily on the crust. In some areas of the region, surface hoar (4-10 mm) has been reported below the recent storm snow in shaded north-facing slopes at upper treeline and above. Large cornices loom over alpine ridgetops. Spring temperatures and sun are producing a melt-freeze snowpack below 1600 m and higher on solar slopes.
Persistent weak layers of surface hoar, crusts, and/or facets 80-120 cm down have been unreactive and no recent avalanches have been reported on these layers.
Terrain and Travel
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Dial back your terrain choices if you are seeing more than 25cm of new snow.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Remain vigilant for changing conditions.
Avalanche Problems
Storm Slabs
Gusty winds will redistribute flurries and dry snow building slabs overnight. Expect slab size and sensitivity to increase as more snow accumulates through the day. Slabs are likely to be most reactive in wind affected areas and below ridges or lee terrain features.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2
Loose Wet
Rain and spring temperatures will warm the snowpack at lower elevations. Be mindful that that any solar input at upper elevations could encourage slab properties to rapidly develop in the new snow.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1.5