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Archived

Avalanche Forecast

Dec 28th, 2018–Dec 29th, 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
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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: Sea To Sky.

Storm snow amounts are uncertain with the latest system passing through Friday night through Saturday. If amounts are locally higher than the forecast indicates, avalanche danger may be HIGH.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

FRIDAY NIGHT: Flurries, accumulation 5-10 cm / Strong southwest wind / Alpine temperature 0 C / Freezing level 1000mSATURDAY: Snow, accumulation 10-20 cm / Moderate to strong southwest wind / Alpine temperature -2 C / freezing level 1500mSUNDAY: Mostly cloudy with sunny breaks / Light to moderate northwest wind / Alpine temperature -5 C / Freezing level 700 mMONDAY: Mix of sun and cloud / Light west wind / Alpine temperature -7 C

Avalanche Summary

Soft storm slabs from Wednesday's storm snow were reactive to skier activity, producing non-destructive, small (size 1) avalanches. Otherwise, no new avalanches were observed. Expect the storm slab activity to increase as new snow begins to accumulate as the latest storm passes through.

Snowpack Summary

Up to 40 cm of low-density snow is poorly bonded to a weak layer of feathery surface hoar, reported to be widespread and 5 to 10 mm in size. Snow amounts will be deepest and touchiest in the lees of terrain features immediately adjacent to ridges.Below 1800 m, around 50 cm of storm snow may not be bonding well to an underlying crust (see here). In other areas, reports indicate that the snow is bonding well to the crust.A weak layer of sugary facets and surface hoar lies around 150 to 200 cm deep in the snowpack. There hasn't been reports of avalanches on this layer for over a week. That being said, this layer may still exist in isolated areas around treeline in some portions of the region.At the base of the snowpack, weak and sugary facets are found below an early-season melt-freeze crust. This weak layer has been the culprit for sporadic, very large avalanches in alpine terrain in the past few weeks. The avalanches have occurred in areas where the ground roughness is very smooth, for example glaciers, firn, and shale/rock slab slopes. An avalanche could be triggered in this layer with a very large trigger, such as a cornice fall.

Avalanche Problems

Storm Slabs

Storm snow accumulating over a newly formed weak layer will require time to bond. Deeper in the storm snow, 50+ cm of snow may not be bonding well to a crust that exists below 1800 m.
Cornices are large and looming near ridges. Give them a wide berth.Use caution in lee areas; thicker deposits are expected due to recent wind loading.Observe for the bond of recent storm snow to underlying surfaces before entering avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2