Parks Canada
Archived Public Avalanche Information

Avalanche Bulletin - Banff, Yoho, and Kootenay National Parks
Issued: Sun Apr 04, 2021 17:02
Valid Until: Mon Apr 05, 2021 17:00

Monday looks like a great day to get out and enjoy the fresh snow on North aspects, just watch for recent wind loading. Start and finish early to optimize travel conditions and minimize any increases in avalanche hazard with day time warming. [CJ]

Danger Ratings: Monday alpine treeline below treeline

alpine: 2 - Moderate
treeline: 1 - Low
below treeline: 1 - Low
Confidence: Moderate - Due to the number of field observations

Problem 1: Wind Slabs
Which Elevation? alpine
Which Slopes? north, northeast, east, southeast
Chance of Avalanches? possible
Expected Size? small - large

New wind slabs have formed in lee areas of the alpine from the new snow and wind on Sunday. These seem to be bonding ok, but may still be triggered by skiers especially at higher elevations where the wind loading was more intense.

Travel and Terrain Advice

    Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.
    Be careful with wind loaded pockets, especially in steep confined alpine terrain.

Problem 2: Wet Loose
Which Elevation? alpine, treeline, below treeline
Which Slopes? west, southwest, south, southeast
Chance of Avalanches? possible
Expected Size? small - small

Strong solar inputs on Monday will increase the likelihood of small loose wet avalanches on steep solar aspects, especially in thin snowpack or rocky areas. Plan your day to avoid this type of terrain as the surface snow warms up.

Travel and Terrain Advice

    Minimize exposure when the solar radiation is strong, especially if snow is moist or wet.

Problem 3: Cornices
Which Elevation? alpine
Which Slopes? north, east, northeast
Chance of Avalanches? possible
Expected Size? small - large

Cornices are big and the springtime is when they fall off more frequently. We have had fairly regular observations of cornice failures over the past few weeks, so minimize your exposure to them especially as the day heats up or the winds increase.
Travel and Terrain Advice

    Cornices become weak with daytime heating, so travel early on exposed slopes.

Weather Forecast

Sunday night will see freezing levels drop to valley bottom and then rise to around 1700 m on Monday, with treeline highs around -4 C. Alpine winds will be in the light to moderate range out of the W and NW. Skies will be mostly clear so solar inputs may be fairly intense despite cooler air temperatures. No precipitation is expected.

Snowpack Discussion

10-20 cm of new snow at treeline over previous crusts and wind effect. New wind slabs forming in alpine lee areas from moderate to strong SW-W winds. Moist snow on all aspects up to 1800 m and higher on solar aspects on Sunday. The March 19 crust interface is down 30-60 cm. Basal facets exist in shallow areas east of the divide.

Avalanche Activity Discussion

On Sunday loose dry sluffing was observed in steep alpine and treeline areas up to size 1.5 in the new snow. Ski hills reported ski and explosive triggered soft wind slabs in lee areas up to size 1.5. One size 3 cornice failure on Vulture Peak near the Wapta Icefields was also reported.