Avalanche Forecast

High -

Monday night: Cloudy with isolated flurries and a trace of new snow. Light west winds.

Tuesday: Mostly cloudy with scattered flurries bringing a trace to 10 cm of new snow, increasing overnight. Light to moderate southwest winds increasing overnight. Alpine high temperatures around -7.

Wednesday: Mainly cloudy with isolated flurries bringing new snow totals to 10-35 cm, continuing overnight. Light to moderate west winds. Alpine high temperatures around -8.

Thursday: A mix of sun and cloud. Variable 3-day snow totals of 15-40 cm. Light northwest winds. Alpine high temperatures around -12.

Recent avalanche activity in the Purcells has been simultaneously impressive and terrifying. Explosive control work in the central portion of the region continues to produce large persistent slab avalanches size 3 and larger on all aspects in alpine terrain. 

Savvy avoidance of suspect avalanche terrain by travelers in the Purcells have kept recent reports of large human triggered avalanches to a minimum, but explosives control missions continue to demonstrate our snowpack's weakness by producing large, deep avalanches.

Common characteristics of recent avalanches in the region include wide propagation, remote triggers and full depth avalanches scouring away the snowpack to ground. Natural avalanches of similar scale have been reported as recently as Friday.

Earlier in the week, there were several instances of large natural events taking out old timber beyond historical avalanche boundaries and running from the high alpine all the way to valley bottom.

The Purcells received 60-120 cm from the big storm two weekends ago. This snow has since settled into a slab over a couple of buried surface hoar layers 70-180 cm below the surface. These layers are expected to be progressively gaining strength, but the character of the lower snowpack complicates matters.

The base of the snowpack in the Purcells is astonishingly weak, much weaker than in an average season. This weakness is widespread across aspects and elevation bands, meaning it's almost everywhere. This basal layer consists of crust, facets and depth hoar. 

With the addition of the new snow last weekend, this weakness became overloaded and its failure has resulted in some spectacularly large and destructive avalanche activity. 

• Stick to simple terrain and be aware of what is above you at all times.
• Very large and destructive avalanches could reach valley bottom.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.