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Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed on
Monday morning, December 20, 2021
Heightened avalanche conditions exist at upper elevations on drifted north-facing slopes where a persistent weak layer of facets near the ground can produce an avalanche. The danger is MODERATE and people could trigger dangerous avalanches remotely from a distance or from below. Avalanches of wind drifted snow are possible in exposed terrain. Slopes in sunny terrain and at lower elevations have less snow and a LOW danger.
Evaluate snow and terrain carefully and avoid drifted slopes, especially up high on shady slopes facing the north half of the compass.
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Weather and Snow
In the last week around three feet of snow with 3 inches of SWE (snow water equivalent) fell at upper elevations in the Bear River Range. Southwest wind picked up again last night, and it is stripping snow off of exposed slopes and depositing it in avalanche starting zones, creating stiff and tricky wind slabs. It will be mostly sunny and breezy again today, with high temperatures near 32°F at 8500' and southwest winds will continue, gusting over 30 mph at times on the ridges. It looks like we will enjoy fair weather through tomorrow before more snow arrives on Wednesday. An active winter weather pattern with periods of heavy snow and strong winds is likely to pick up steam on Thursday and continue through at least Christmas Day, with significant snow accumulations likely.
Recent Avalanches
A couple skier triggered avalanches occurred Saturday in high north facing terrain. The largest was likely remotely triggered as it was observed near an uptrack near the Tony Grove-Blind Hollow Saddle at about 8800' on a north facing slope. The 2 to 3 foot deep avalanches appear to be failing on a persistent weak layer consisting of sugary faceted snow near the ground.
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
On north facing slopes above 8000 ft, old snow became weak and faceted in some places and will produce a soft slab avalanche. This persistent weak layer does not exist everywhere, and we're still trying to determine where it does and doesn't exist. In many places the old snow from October and early November is capped by a hard ice/rain/rime crust and December snow is well bonded to it. Other slopes have a thin layer of small facets above this crust and the December snow is not well bonded to it.
Friday on Red Pine Ridge and near Logan Peak, we were hunting for this weak layer. Even though we could only find it in a few places, for now the only safe option is to assume it exists until proven otherwise, and avoid avalanche terrain on north facing slopes.
  • People are triggering audible collapses or "whumpfs" in the backcountry. These heart-stopping booming noises indicate unstable snow and potential for dangerous avalanches failing on a persistent weak layer.
  • Collapses are often accompanied by shooting cracks in the snow surface. Recently, we've seen some of these extend hundreds of feet away from where we trigger the collapse.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
There has been a lot of wind in the last few days, and soft and harder slabs of wind drifted snow may still produce avalanches. Fortunately these drifts are somewhat easy to see and avoid. The picture below shows what these drifts look like (wind was blowing from right to left in the photo).
Incessant strong southwest winds created stiff drifts in upper elevation terrain.
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.
  • The Tony Grove Road is not maintained for wheeled vehicles in the winter season.
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.
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