Issued by Toby Weed on Wednesday morning, December 29, 2021
Dangerous avalanche conditions and CONSIDERABLE danger exist on north facing slopes at upper and mid elevations in the backcountry. People are likely to trigger dangerous avalanches failing on a buried persistent weak layer near the ground. Recent drifting created heightened avalanche conditions on steep slopes at all elevations, and people could trigger avalanches of wind drifted snow. Conditions are much safer and quality powder riding can be found in low angled terrain off of and out from under slopes steeper than about 30 degrees.
Continue to avoid and stay out from under north facing slopes steeper than about 30°
We enjoyed a break in the stormy weather yesterday, with no new snow in the last 24 hrs. But it is snowing again this morning in the Central Bear River Range, and a few inches could accumulate today before another stormy night with heavy snow and strong winds. The Christmas storms brought a few feet of snow to upper elevation slopes, and close to 5" of SWE was recorded at local Snotel sites. After drifting snow at all elevations, incessent southwest winds eased off yesterday. This morning winds are increasing a little and blowing from the west around 25 mph with gusts around 35 mph at the 9700' CSI Logan Peak weather station. I'm reading 4°F at Tony Grove and -1°F at Logan Peak.
Expect periods of snowfall, drifting from west winds, and very cold temperatures in the mountains again today, with high temperatures around 17°F at 8500', 25 mph west winds on the ridges, and wind chill values around -15°F.
Mark and I went for a ride out of Beaver Creek TH yesterday. We traveled over Danish Pass and found pretty nice powder riding conditions in Egan Basin and upper Franklin Basin. We saw evidence of a couple recent natural avalanches, triggered a couple collapses or whumpfs in the flats, and found the buried persistent weak layer of concern in north facing terrain. We also found great powder conditions in low angled terrain and good stability on slopes not facing north.
Here is a look at what I found during the storm Monday in the Central Bear River Range....
Recent Avalanches
There were a few large natural avalanches that occurred during the Christmas storms. We think these failed on a buried persitent weak layer and occurred on upper elevation north facing slopes late on or around 12/24, (Christmas Eve), but the crowns and debris from these avalanches is blown in and covered up by a couple feet of new snow.
Check HERE for all the latest observations and avalanche activity.
Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Dangerous deep slab avalanches breaking on a persistent weak layer near the ground are likely for people to trigger. This layer of weak, sugary facets can be found in north facing terrain 6-12 inches above the ground just above a hard ice crust that caps old snow from October and early November. Avalanches failing on this layer will likely be 3 to 5 feet deep and may break hundreds of feet across. Avalanches could still be triggered remotely from a distance, or worse, from below.
Audible collapses or "whumpfs" and shooting cracks are red flags indicating unstable snow and a lurking persistent weak layer.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Winds blowing from the south, southwest, and west have been transporting tremendous amounts of snow during the last several days. Monday the winds dropped down into the terrain, and we observed significant drifting at all elevations. The wind slabs appear to be well bonded the the fresh snow in most areas, but in some areas, around terrain features where drifts form, people could trigger avalanches.
Winds during the storm drifted snow directly onto slopes that have a persistent weak layer of sugary facets near the ground. Wind slabs will make avalanches breaking on the facets larger, deeper, and more deadly.
These appeared to be bonding pretty well yesterday, but avalanches of wind drifted snow are possible where there is no apparent faceted persistent weak layer. Avalanches at any elevation could fail on a density change within drifted new snow or on a thin, or a not-so-obvious weak layer.
Additional Information
Always follow safe backcountry travel protocols. Go one person at a time in avalanche terrain, while the rest of your party watches from a safe area.
Check your avalanche rescue equipment, change your batteries, and practice often with your backcountry partners.
Be very careful, keep your speed down, and stay in control. Encounters with shallowly buried rocks or down trees in the early season have led to many season-ending injuries.
General Announcements
Who's up for some free avalanche training? Get a refresher, become better prepared for an upcoming avalanche class, or just boost your skills. Go to https://learn.kbyg.org/ and scroll down to Step 2 for a series of interactive online avalanche courses produced by the UAC.
Check out all the upcoming education classes and clinics HERE.
Please submit your observations from the backcountry HERE.
This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.
