The possibility remains to trigger a LARGE and deadly avalanche today. Observations of large collapses and cracking snow from around our region yesterday demonstrate that we are not into the clear yet. The safest riding conditions will be found in lower angled slopes away from, and out from underneath, steep start zones.
?
Above 6500 ft.
?
5000-6500 ft.
?
3500-5000 ft.
Whumpfing, collapsing, and cracking are all signs of instability. Although we haven’t had any avalanches reported since Saturday night’s natural cycle, the continued stream of scary collapses should catch your attention. Had the reporting parties been on slopes steeper than 35 degrees, it likely would have resulted in an avalanche. These LARGE avalanches are likely to be 1-3 feet thick, failing on one of several buried weak layers. Faceted crusts are widely distributed throughout our mid and upper elevations and surface hoar is lurking in some sheltered areas. The unpredictable nature of this avalanche problem can surprise you by breaking far above you, or you can trigger them remotely from adjacent slopes.
The avalanche activity from November on Heavens Peak makes it clear that with additional new snow and wind on top of our pre-built slab could produce avalanches up to 5 feet thick. We also noted what looked to be a step-down avalanche involving most of the season’s snowpack on Great Northern which ran this weekend. Areas that are more likely to trigger one of these VERY LARGE avalanches are in shallow spots or near rock outcroppings. Uncertainty persists as we have yet to gain many observations from our alpine terrain. With uncertainty comes conservative decision making.
Nothing can be more inviting than a fresh blanket of new snow over mountainous terrain unless that blanket is sitting on a persistent week layer. Though we have not heard about any human triggered avalanches since the storm ended on Sunday morning, riders continue to report signs of instability throughout the region. The big collapses and shooting cracks tell us that avalanches are still sensitive to human triggers.
Riders near China basin reported whumpfing and collapsing as they traveled around 5,000 to 5,500 ft in elevation. At similar elevations near Marias Pass, we noted numerous cracks breaking away from our skis, as well as propagating extended column tests at 5,800 ft. These are likely failing on either the surface hoar that was buried November 23, or near the faceted crust that was buried on November 19. On the other end of the spectrum, riders did report stable conditions in areas of the Swan, and Blase noted an unreactive snowpack in his tour in the Southern Whitefish Range. These are classic examples of how these persistent avalanches behave — peak sensitivity during and just after the storm, followed by inconsistent feedback shortly after that, with spatial variability from slope to slope or basin to basin. What we do know is that it is still possible to collapse and propagate one of these persistent week layers. There are differences in slab and weak layer characteristics that make some slopes more problematic than others right now. These can be difficult to assess, however, your silver bullet right now is to manage slope angle.
If your snowpack assessments are suggesting you can travel into avalanche terrain today, remember a few critical points about managing your team and your terrain. Travel one at a time, keep eyes on your partners and have an exit plan. Don’t forget to do your beacon and equipment checks before leaving the vehicle. Manage your terrain by selecting terrain with gradual runouts. By doing so, you are avoiding terrain traps such as gullies, cliffs, and treed areas. Remember that a ride early season can cause significant trauma as it rakes you through stumps, rocks, and logs.
Today we will see lingering flurries as northwest flow sets in over the area. Expect mostly cloudy skies with temperatures in the mid to upper 20s. Winds will be light with some stronger gusts out of the southwest.
| Tuesday | Tuesday Night | Wednesday | |
|---|---|---|---|
| Cloud Cover: | Mostly cloudy | Overcast | Mostly Cloudy |
| Temperatures: | 23 to 29 deg. F. | 17 to 22 deg. F. | 24 to 30 deg. F. |
| Wind Direction: | West | SouthWest | West |
| Wind Speed: | 5 to 15, G30 | 10-20, G30 | 10-20, G35 |
| Snowfall: | 0 in. | 0-1 in. | 0-1 in. |
| Snow Line: | 2500 | 2000 | 2500 |
This forecast applies only to backcountry areas outside established ski area boundaries. The forecast describes general avalanche conditions and local variations always occur. This forecast expires at midnight on the posted day unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.
