Avalanche Forecast

Issued: Dec 21st, 2020 8:00AM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Chris Gooliaff,

Glacier.

One more storm before Santa gets a weather window to deliver powder faceshots.

With the arrival of the afternoon storm, danger levels will bump up as a natural avalanche cycle rips through the area.

Perhaps it's best to go sample your ski hill today!

Summary

Weather Forecast

A storm tracking along the international border will spin some snow and reverse (N and E) winds our way.

Today: Snow starting near noon, 10-15cm, mod E winds, FZL 1000m

Tonight: Snow,10cm, FZL at valley bottom, mod N ridge-top winds.

Tues: Cloudy with sunny periods, nil snow, FZL 500m, light NW winds

Wed: Mix of sun/cloud, FZL in valley, light SW winds

Snowpack Summary

125cm of snow over the last 5 days, along with strong S-SW winds and warm temps, has created a sensitive slab at all elevations. The Dec 13 surface hoar/facets are down 90cm+ and the Dec 7 crust/surface hoar layer is down 100cm+. The Nov 5 crust lingers near the base of the snowpack and several avalanches over the storm period stepped down to it.

Avalanche Summary

A brief respite in the natural avalanche cycle this morning, but we expect it to pick up with the afternoon storm.

A widespread cycle of natural and artillery controlled avalanches up to size 3.5 occurred in the highway corridor (and likely in the backcountry) Saturday morning.

Confidence

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

Problems

Storm Slabs

Continuing snowfall, mod/strong W'ly winds, and mild temps have created widespread, reactive storm slabs easily triggered by a person.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1.5 - 3

Persistent Slabs

1m+ sits on persistent layers of rain crust/ surface hoar/ or suncrust. Storm slabs have the potential to step down to these interfaces, triggering very large avalanches.

Be aware of the potential for wide propagations.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Dec 22nd, 2020 8:00AM