Purcells

The bulletin is based on limited data. Local variation in conditions and danger levels are likely to exist. To produce more accurate forecasts, we need information. Please send an email to [email protected].

Fair - Intensity of incoming weather is uncertain

An intense system is moving across the interior ranges today bringing heavy precipitation amounts, rising freezing levels and strong ridgetop southerly-southwesterly winds. Freezing levels could rise to 1900m on Wednesday, then fall to 800m before the next system passes. Thursday and Friday we should see freezing levels hover at valley bottom and accompanied by steady light to moderate precipitation.

Avalanche observations from the Purcells today include explosive work which produced avalanches up to size 2.5 with wide propagation, and running far. These avalanches were failing on the predominant facet layers above the ground. A natural size 2.0 avalanche was reported in the alpine today but with very limited observation to go off. I'm sure the visibility was not cooperative.

November 22 update, there may be up to 30cm of new storm snow in sheltered areas, and variable wind slab formation on all exposed areas. The average, snowpack depths are looking like 60-80cm at treeline and probably 100-140.November 21 discussion, distribution is highly variable, so on a small scale you'll likely see bare ground beside areas with well over 200cm of snow while on a larger scale, one mountain or drainage may have significantly more or less than the next.. I expect the storm and wind slabs to be reactive for the next few days. There's some potential problems at the old/new interface and in the mid-pack including thin crusts and the November surface hoar, on which I think there is now general agreement that it's November 7th and is a persistent weak layer. It may not last as long as true winter surface hoar but it's down 100cm and has been around for 2 weeks so I guess a PWL it is. Even if these layers seem like they've died down a bit in the last few days, I suspect they'll reactivate in the next couple of days, perhaps not on a widespread basis but certainly locally on specific terrain (e.g. especially where no previous activity occurred). The deep snowpack is a bit of a mixed bag well facetted near the ground in many areas although it's possible this is less the case in places where the snowpack depths are deeper. This is a general overview--I'm hesitant to get too specific this early in the season when data is sparse and there's so much variability. If you think I'm out to lunch and want to set me straight: [email protected].