Avalanche Forecast

Archived

Feb 26th, 2023–Feb 27th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

Use caution in wind loaded areas where slabs are deeper, more cohesive slabs and may be reactive to human traffic.

Confidence

Moderate

Avalanche Summary

No new avalanches were reported in the region in the last few days. Backcountry users should expect to see evidence of a small natural wind slab avalanche cycle at higher elevations from recent strong winds.

Please post your field observations and photos on the Mountain Information Network. The information is beneficial to forecasters and fellow backcountry users.

Snowpack Summary

5-10 cm of storm snow sits on wind affected surfaces at all elevations. Deeper deposits may be found in north and east facing terrain features due to southwest winds.

The mid-snowpack is generally well settled, with no current layers of concern.

The lower snowpack includes a layer of weak sugary crystals and crusts near the ground. These facets are slowly gaining strength and have not produced recent avalanche activity. We continue to track the layer and watch for any signs that it could wake up and produce very large avalanches.

Weather Summary

Sunday Night

Cloudy with isolated flurries, 1-5 cm accumulation. Westerley ridgetop wind 25-40 km/h. Freezing levels drop to the valley bottom. Alpine high of -9 °C.

Monday

Partly cloudy with isolated flurries, 2-3 cm. Southwesterly ridgetop wind 25 km/h. Freezing levels around 700 m. Alpine high of -6 °C.

Cloudy with scattered flurries this evening 5-10 cm.

Tuesday

Mainly cloudy with isolated flurries, 2-3 cm accumulation. Southwesterly ridgetop wind 25 km/h. Freezing levels around 500 m. Alpine high of -6 °C.

Wednesday

Cloudy with sunny periods and isolated flurries, trace accumulation. Westerley ridgetop wind 25-40 km/h. Alpine high of -5 °C. Freezing levels 700 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be carefull around freshly wind loaded features.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.