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Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed on
Thursday morning, December 16, 2021
Dangerous avalanche conditions exist, and there is CONSIDERABLE danger in the backcountry. Avalanches in north facing terrain may fail on a buried persistent weak layer and could be triggered remotely, from a distance, or below. People are likely to trigger slab avalanches of wind drifted snow in exposed terrain, as well as soft slab and loose avalanches of storm snow on steep slopes at upper elevations. Natural avalanches are possible, particularly during periods of heavy snowfall.
  • People should avoid travel on or under steep drifted slopes at upper and mid elevations.
  • Southerly facing and lower elevation terrain was bare or very shallow before last week's storm, so avalanches are unlikely in these areas, and the danger remains LOW.
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Weather and Snow
You might need to pack an extra pair goggles. Expect a very cold and snowy day in the mountains today, with sub-zero temperatures, fairly strong westerly winds, wind chill values as low as -27° F, 7 to 11 inches of accumulation possible on upper elevation slopes by this evening and snowfall continuing tonight.
Winds blowing out of the southwest drifted plenty snow in exposed terrain overnight, and drifting of today's new snow will continue to build wind slabs on the downwind side of ridges and in and around terrain features. Dangerous avalanche conditions exist in the backcountry, mainly in northerly facing upper elevation terrain where avalanches could fail on a buried persistent weak layer. Human triggered avalanches are likely and natural avalanches are possible especially during periods of heavy snowfall.
***Sunny slopes up high and most slopes below about 8000' were bare of snow before last week's storm.
Recent Avalanches
Yesterday, I came across a couple natural avalanches near Tony Grove Lake, which occurred during the storm overnight Tuesday night. The avalanches that were around a foot deep failed on a buried persistent weak layer of sugary faceted snow under last week's storm snow.
This natural avalanche above the southwest corner of Tony Grove Lake is about a foot deep and 100' wide, NE, 8300'
On Monday, backcountry skiers spotted a recent natural avalanche of wind drifted snow in the Grandfather Cornice Area of Cornice Ridge. The 2' deep and 100' wide avalanche occurred on a northeast facing slope at around 9300' in elevation.
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
In north facing terrain above about 8000', some avalanches are likely to fail on a persistent weak layer consisting of sugary faceted grains. Yesterday, I triggered several large and loud collapses in low angled terrain and around rock out-croppings as I traveled in untracked snow west of Tony Grove Lake.
  • Audible collapsing or "whumpfs" are a sign of unstable snow and of an active persistent weak layer problem.
  • Cracking in the snow surface is a sure sign of unstable snow.
  • Avalanches failing on this persistent weak layer could be triggered remotely, from a distance, or below.
I triggered a loud whumpf on the flats and this thin crack formed about 60' away from me.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
The CSI Logan Peak wind sensor at 9700' shows continuing strong winds blowing from the southwest this morning...
  • People are likely to trigger soft slab avalanches of wind drifted fresh snow at upper elevations where the winds contiue to create drifts.
  • Avalanches of wind drifted snow could be 1 to 3-feet-deep.
  • Wind slab avalanches could fail on a persistent weak layer, and might be triggered remotely.
  • Avoid recently drifted snow in and around terrain features like gullies, sub-ridges, and cliff bands.
Avalanche Problem #3
New Snow
Type
Location
Likelihood
Size
Description
As fresh snow piles up today, people are likely to trigger soft slab and loose avalanches of storm snow in steep terrain at upper and mid elevations. Avalanches could fail on desity changes or other weak layers within the storm snow itself.
  • Natural avalanches are possible during periods of heavy snowfall.
  • Even small avalanches could be quite dangerous due to very shallow snow conditions.
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
Get free batteries for your transceiver and a chance to win 1 of 10 Black Diamond Rescue Kits, 1 of 3 Mammut Barryvox transceivers, or 1 of 3 BCA Tracker transceivers. Stop at a participating shop, fill out our survey and get a free set of batteries. Don't need batteries, but still want a chance to win? Simply fill out the survey to be registered. Promotion runs through December 19.
  • Check out all the upcoming education classes and clinics HERE.
  • Please submit your observations from the backcountry HERE.
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