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Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed on
Thursday morning, December 17, 2020
Heavy snowfall and drifting from southwest winds will overload a preexisting persistent weak layer of sugary faceted snow, the danger will rise to CONSIDERABLE during the day, and dangerous avalanche conditions will develop on many upper and mid elevation slopes.
PEOPLE ARE LIKELY TO TRIGGER DANGEROUS AVALANCHES!
  • Avalanches could be triggered remotely or from a distance.
  • Evaluate snow and terrain carefully, make conservative decisions, and stay off and out from under steep drifted slopes.
  • You will find safer conditions in sheltered, low angle, and lower elevation terrain.
Low
Moderate
Considerable
High
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Learn how to read the forecast here
Avalanche Watch
THE AVALANCHE DANGER FOR THE WARNING AREA WILL LIKELY RISE TO HIGH OVER THE NEXT SEVERAL DAYS.
AVALANCHE WATCH IS FROM 6 AM MST THIS MORNING TO 6 AM MST FRIDAY. FOR THE MOUNTAINS OF NORTHERN AND CENTRAL UTAH INCLUDING THE BEAR RIVER RANGE...THE WASATCH RANGE...THE WESTERN UINTAS...AND THE MANTI-SKYLINE PLATEAU.
DANGEROUS AVALANCHE CONDITIONS EXIST ON ALL STEEP SLOPES. STAY OFF OF AND OUT FROM UNDERNEATH SLOPES STEEPER THAN 30 DEGREES.
Special Announcements
Beaver Mountain will be closed to uphill travel this weekend, starting tomorrow, so the crew can set up for opening day on Tuesday.
Weather and Snow
The National Weather Service has issued a Winter Weather Advisory for the mountains, beginning this morning and extending through early Friday morning. Expect the avalanche danger to rise and become more widespread in the backcountry as heavy snow accumulates and is drifted onto steep mountain slopes, overloading the sugary preexisting weak snow from November.
Currently, hitting rocks or other shallowly buried obstacles presents a significant hazard. A few inches of nice light powder now obscures many hazards. Most slopes have little more than about 2' of total snow, and a steep temperature gradient is turning the shallow snow into loose sugary or faceted grains. In many places, the weak snow is easy to punch through to the rocks below.
A thick layer of very weak, sugary, or faceted snow will likely be a problematic persistent weak layer on many slopes, as future snow overloads it.
Recent Avalanches
Tuesday, a local skier reported triggering a small soft slab avalanche running on the faceted snow on a very steep slope south of Tony Grove Lake. Even though the new snow is shallow and soft, and the skier was not caught, the avalanche entrained a surprising amount of snow and slammed into the trees below with a good deal of force.
On a nearby steep slope yesterday, a pow surfer intentionally triggered a few stiffer wind slab avalanches that entrained a good deal of snow, running through the trees. The dangerous avalanches were quite easy to trigger, failing on weak sugary November snow..
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
People could trigger wind slab avalanches on steep upper and mid elevation slopes where drifts formed on weak, sugary or faceted snow. In more sheltered terrain, loose sluffs and shallow soft slabs of new snow are possible for people to trigger because the older snow underneath is very weak, faceted, and loose.
  • Even a small avalanche could be very dangerous due to shallow early season snow conditions. You do not want to get caught and carried over rocks or strained through bushes and stumps, so it's best to avoid travel on all steep drifted slopes.
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
During the extended November dry spell, the shallow snow on the ground was subjected to a significant temperature gradient and resulting sublimation caused the snow on many slopes to become sugary, non-cohesive, faceted, and very weak. Drifted snow is a wind slab and when stiffer, more cohesive slabs develop on top of weak, sugary, faceted snow they are unstable. Many slopes in the region are now plagued by weak faceted snow, but most do not yet have a slab layer formed on top of it.
  • Avalanches failing on a persistent weak layer can be very sensitive, and they might be triggered remotely, from a distance, or worse from below!
Additional Information
Everybody should make time to examine and practice with your avalanche rescue equipment, and convince your backcountry partners to practice with you. Watch our companion rescue video HERE
My tip for avoiding avalanches in the backcountry is to keep your slope angles low. Avoid and stay out from under slopes steeper than about 30 degrees. Get a tool to measure slope angle and practice with it in the backcountry. Watch the video HERE.
General Announcements
Visit this website with information about Responsible Winter Recreation by the Utah Office of Outdoor Recreation.
We've kicked off Season 4 of the UAC podcast with a Conversation with American Avalanche Institute owner Sarah Carpenter. You can stream it HERE or wherever you get your favorite podcasts.
The Tony Grove Road is not maintained for wheeled vehicles in the winter.
EMAIL ADVISORY. If you would like to get the daily advisory by email you subscribe HERE.
Remember your information can save lives. If you see anything we should know about, please help us out by submitting snow and avalanche observations....HERE. You can also call us at 801-524-5304, email by clicking HERE, or include #utavy in your tweet or Instagram.
I will update this forecast by around 7:30 tomorrow morning.
This forecast is from the USDA Forest Service, which is solely responsible for its content. The forecast describes general avalanche conditions and local variations always occur.
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