Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 2nd, 2018–Jan 3rd, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Rockies.

We're into a tricky period as a critical amount of storm snow settles (into a slab) and sits on a buried weak layer. Keep your terrain choices on the conservative side until conditions stabilize.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Dry with gradually warming alpine temperatures during the week. Cold in the valley bottoms. WEDNESDAY: Cloudy with sunny breaks. Ridge wind light west. Alpine temperature -5. Freezing level surface.THURSDAY: Mix of sun and cloud. Ridge wind light southwest. Alpine temperature -5. Freezing level surface.FRIDAY: Cloudy with isolated flurries. Ridge wind light west. Alpine temperature -3. Freezing level surface.

Avalanche Summary

On Monday, a machine triggered Size 1.5 persistent slab avalanche was reported running on the mid December surface hoar layer, down 35 cm at that location (1700m). Even mountain goats looked like they were triggering avalanches! See the details here in the MIN post. On Sunday a Size 2 persistent slab (stepping down to late November crust/facets) was intentionally triggered on an east aspect near 2000m in the south of the region.On Saturday several natural and human triggered storm slab avalanches to Size 2 were reported on a wide variety of aspects and elevations. Furthermore, several persistent slab avalanches to Size 1.5 were reported (with some remote-triggered by skiers). A week ago, a larger persistent slab (Size 2) was triggered low on a slope that propagated up and across the slope on a 50 cm deep crust. This highlights the potential for persistent slab avalanches to have wide propagations.

Snowpack Summary

Up to 45 cm of snow fell on at the end of last week. Since then, strong winds from a wide range of directions have blown snow around: In the south of the region winds were from the south west; whereas in the north the winds were from the north east. The main question in the snowpack surrounds the mid-December layer sitting beneath the recent snow. This layer includes crusts on solar aspects and feathery surface hoar in sheltered terrain at and below treeline, and has consistently shown its reactivity, even on small features below treeline. The lower snowpack is composed of mostly soft sugary snow and a few early season crusts that have not produced significant test results recently.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.