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Avalanche Forecast

Jan 17th, 2019–Jan 18th, 2019
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
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.

Modest snowfall is gradually burying a new weak layer, while triggering large avalanches is still possible in steep rocky terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

THURSDAY NIGHT: Light flurries with localized accumulations of 5-10 cm, moderate west wind increasing in speed overnight, alpine temperatures drop to -16 C.FRIDAY: Mostly cloudy with isolated flurries, strong west wind, alpine high temperatures around -6 C.SATURDAY: 5-15 cm of snow, strong southwest wind, freezing level climbing to 1500 m, alpine high temperatures around -4 C.SUNDAY: Mostly cloudy then clearing in the afternoon, strong west wind, alpine high temperatures around -6 C.

Avalanche Summary

By Thursday afternoon, skier traffic produced a few small (size 1) avalanches in the new snow.The most recent reports of larger avalanches are from last weekend when warm temperatures stressed some of the deeper layers in the snowpack. On Saturday, a size 2 natural deep persistent slab avalanche was observed on a south facing slope at 2100 m (more details here). There is also a great MIN report from the neighboring Lizard Range where a group of sledders share about their near miss on a steep southwest facing feature at ridgecrest.

Snowpack Summary

The new snow is burying large surface hoar crystals and/or sun crusts, which could eventually develop into a touchy problem as snow accumulates. The most suspect terrain features will be steep slopes and rolls below 2000 m (where the largest surface hoar exists) and steep south-facing slopes in the alpine (where sun crusts exist).Large variability in snow depths still exists in the region, ranging from almost no snow to nearly 200 cm in some areas. For average snowpack areas, expect to find weak and sugary faceted snow around 50 to 100 cm deep, which extend to the ground. This weak bottom half of the snowpack has been the culprit for large avalanches in the region over the past few weeks.

Avalanche Problems

Wind Slabs

New snow is gradually accumulating above weak surface hoar and/or crusts. On Friday, wind loaded slopes may have enough snow above this layer for small avalanches.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Deep Persistent Slabs

Deeply buried weak layers remain a concern. These layers are more easily triggered in areas where the snowpack is shallow, such as near ridges and rocky terrain.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid steep slopes in areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3