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Archived

Avalanche Forecast

Jan 11th, 2018–Jan 12th, 2018
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high

Regions: Glacier.

Continued elevated danger of skier and rider triggered avalanches today.  It is time for very conservative route selection.

Weather Forecast

Cloudy with sunny periods and an alpine high of -10C today.  Scattered flurries with a slowly rising freezing level and warming trend into the weekend. Potential for another 10cm of snow by Saturday. This additional load and warming will keep the snowpack weak layers touchy.

Snowpack Summary

We have three buried surface hoar layers two of which are touchy and sensitive to human triggering. Jan 4th surface hoar is down ~45cm and the Dec 15 surface hoar Persistent Weak Layer down ~100cm are ripe and ready to slide. Snowpack tests show propagation potential with sudden planar results on the Jan 4 and Dec15 layers.

Avalanche Summary

Several reports of skier triggered slides occurred yesterday. A size 2 slide at the top of Grizzly Shoulder, East aspect and 30 degree slope was 80m wide, 40cm deep and ran 80m down slope. A remote triggered size 1.5 slide at 1750m 1m deep, 25m wide and ran for 150m taking out part of the ski track. Several slides to size 2.5 in hwy corridor.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Avalanche Problems

Storm Slabs

45cm of recent storm snow has settled into a slab. The Jan 4 surface hoar is down ~45cm and found to be up to 15mm in size. If triggered, avalanches could step down to the Dec 15th PWL with potential for large avalanches.
Watch for whumpfing, hollow sounds, and shooting cracks.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3

Persistent Slabs

The Dec 15th PWL is widespread around tree line and below tree line, buried ~100cm. Previous warm temps have slabbed up the upper snow pack. This interface is reactive with skier remote slides Wednesday and a skier buried in a terrain trap on Monday.
Be aware of the potential for wide propagations.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3