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Avalanche Forecast

Apr 17th, 2021–Apr 18th, 2021
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: South Rockies.

An upslope storm is forecast to bring up to 30 cm of new snow to favored areas. Watch for storm slabs building throughout the day and dial back terrain choices where you find more than 20 cm of new snow.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

An upslope storm will bring varying snow totals to the region, favoring the eastern slopes.

Saturday night: Mostly clear, light northwest wind, alpine temperature near 0 C, freezing level 2900 m.

Sunday: Cloudy, 10-25 cm of snow, winds becoming northeast and increasing to moderate, alpine high temperature +1 C, freezing level dropping through the day to 1000 m.

Monday: Mostly cloudy, light northerly winds, alpine high temperature -2 C, freezing level 1700 m.

Tuesday: Mainly sunny, light southerly winds, alpine high temperature -2 C, freezing level 2300 m. 

Avalanche Summary

On Saturday, there were reports of numerous wet loose avalanches releasing naturally on steep east-facing alpine slopes early in the day. Observers also reported two natural wet slab avalanches that occurred on northeast aspects above 2000 m.

Snowpack Summary

An upslope storm is expected to bring moderate northeast winds and enhanced snowfall to the eastern slopes throughout the day on Sunday. Amounts will generally be near 10 cm with pockets of up to 30 cm in favored areas. A new storm slab problem will likely build throughout the day as snow accumulates. Precipitation will likely start as rain, further complicating the amount of snow forecast. Cornices are large and fragile. Cornice falls could trigger avalanches on the slopes below.

The snowpack is overall strong and settled in most areas. However, steep and rocky alpine slopes with a shallow or thin to thick snowpack may still harbor deeply buried weak layers.

The snow line is slowly creeping up the mountains, making some access areas snow-free. 

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • Extra caution is needed around cornices under the current conditions.

Avalanche Problems

Storm Slabs

Snow totals are expected to vary across the region, but areas that see upslope enhancement may receive up to 30 cm accumulate by late afternoon on Sunday. The new snow will likely form a reactive storm slab problem that will be touchier in wind-drifted areas.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Cornices

Strong solar radiation and continued warming may trigger the large cornices that hang over ridge lines. Cornice falls are a hazard on their own, but could also trigger avalanches on the slopes below.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine.

Likelihood: Likely

Expected Size: 2 - 3