Likelihood ?CertainVery LikelyLikelyPossible
Size ?HistoricVery LargeLarge
There is a consistent weak spot in the snowpack approximately 1 foot below the surface that sits under the week-old storm snow interface. It is unlikely to cause a problem moving forward and continues to strengthen with time. This layer shows up consistently across the area in compression tests but shows very-low likelihood of propagation or triggering an avalanche.
Early last week the area started out with significant wind loading and storm slab issues and those problems have all settled down and left us with a very stable snowpack on Monday. Yesterdays results and observations all inspired more confidence in our snowpacks strength. The only consistent failure I have been seeing is in the interface under the last storm snow but it is not a big concern as it is unlikely to propagate and has gained alot of strength with a week of mild temperatures. Some of the deeper weak layers that we have been tracking all season consist of the November 19th rain crust and buried surface hoar from early January. The crust layer is still easy to get to in the thin snowpack of the Purcell Range but is highly unlikely to fail without a significant weather change such as a rain on snow event. I have not been able to find the buried surface hoar layer out there this past week despite extensive effort. It is deep and likley smashed by the multiple storm events we have seen in the past couple of weeks.
My concern right now is moving forward into Wednesday. On Monday we found crust layers on south and west aspects in open terrain and much of the shaded terrain had a very small layer of surface hoar growing on the snowpack. This will cause us some problems by Wednesday morning. Discussions with the Weather Service indicate that we can expect dense snow to fall mostly after mid-night at upper elevations in the East and West Cabinets. Between 4-8" will likely be the case with higher amounts on the highest peaks. It's not alot of snow; but, it's enough to take you for a ride and I expect it to be pretty reactive with the current bed surface that it will be resting on. The good news is that these surface instabilities will be easy to spot as you travel and will likely show themselves as you travel around. So, use caution on Wednesday and avoid steep terrain if you are seeing any signs of slab development, natural avalanches or cracking underfoot as you travel around.
The other problem we may see in the coming week will be temperature related. It appears that our "January Thaw" is coming and I would also anticipate the possibility of "loose-wet" avalanches below 5,000' later in the week. With a little new snow on a melt-freeze crust this problem will be most reactive on south and west aspects.
We observed multiple avalanche crowns yesterday that were all older and mostly buried by the last storm cycle. The biggest one on Bockman Peak can be seen in this photo. It released at about 7,000' and stepped down to a deeper layer on the left flank.
Big thanks to all of you that showed up for the "Intro to Avalanches" class on Friday and Saturday!!
Backcountry Forecast from NWS Missoula issued: 340 AM MST Tue Jan 21 2020 DISCUSSION: NORTHWEST MONTANA: Overall a warm weather pattern continues into next weekend. Light, nearly continuous precipitation will continue through most of the week with the heaviest amounts tonight and then Thursday night to a lesser degree. Snow levels will peak just below 5,000 feet Wednesday night causing some light rain or drizzle on the mid-slopes and dense snow with low snow ratios at the higher elevations. Most precipitation will fall in the Kootenai-Cabinet region with much less in the Glacier Park region.
Kootenai: --------------------------- 5000-7000 FT ---------------------------- Today Tonight Wed Cloud Cover 75% 95% 95% Hi/Lo Temps 29 to 35 22 to 28 26 to 33 Winds(mph) S 14G32 SW 23G40 SW 18G37 Precip Chc 90 70 70 Precip Type snow snow snow Liquid Amt 0.16 0.29 0.09 Snow Ratio(SLR) 15:1 16:1 16:1 Snow Amt(in) 2-5 4-14 1-6 Snow Level 3500 3000 2000
Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit. For a recorded version of the Avalanche Advisory call (208)765-7323.
This website is owned and maintained by the Friends of the Idaho Panhandle Avalanche Center. Some of the content is updated by the USDA avalanche forecasters including the forecasts and some observational data. The USDA is not responsible for any advertising, fund-raising events/information, or sponsorship information, or other content not related to the forecasts and the data pertaining to the forecasts.