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Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed on
Friday morning, December 18, 2020
Heavy snowfall and drifting overloaded a preexisting persistent weak layer, and HIGH avalanche danger exists on many upper elevation slopes. Natural avalanches are possible, and dangerous avalanche conditions with CONSIDERABLE danger is widespread at upper and mid elevations.
PEOPLE ARE LIKELY TO TRIGGER DANGEROUS AVALANCHES!
  • Avalanches could be triggered remotely or from a distance.
  • Avoid travel in avalanche terrain today. Stay off and out from under all slopes steeper than about 30 degrees.
Low
Moderate
Considerable
High
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Avalanche Warning
THE AVALANCHE DANGER FOR THE MOUNTAINS OF NORTHERN AND CENTRAL UTAH, INCLUDING THE WASATCH RANGE...THE BEAR RIVER RANGE< THE WESTERN UINTAS AND THE MANTI-SKYLINE PLATEAU IS HIGH. RECENT HEAVY SNOWFALL AND DRIFTING FROM STRONG WINDS HAS CREATED WIDESPREAD AREAS OF UNSTABLE SNOW. HUMAN TRIGGERED AND NATURAL AVALANCHES ARE LIKELY. TRAVEL IN AVALANCHE TERRAIN IS NOT RECOMMENDED. STAY OFF OF AND OUT FROM UNDERNEATH SLOPES STEEPER THAN 30 DEGREES.
Special Announcements
Beaver Mountain is closed to uphill travel so the crew can set up for opening day on Tuesday.
Weather and Snow
Heavy snow accumulated and was drifted onto steep mountain slopes with yesterday's storm, overloading widespread sugary preexisting weak snow from November.
Before the storm most slopes had little more than about 2' of total snow, and a steep temperature gradient turned 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.
Expect mostly cloudy and cold conditions in the mountains today, with a north wind around 15 mph blowing along the ridges, and wind chill values around -3°F. Clouds will remain over the zone through the weekend and it will be pretty cold, with a chance for some snow showers on Sunday.
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 Wednesday, a powder 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..
Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Many slopes in the region are plagued by layers of weak faceted snow formed during the prolonged November dry spell.
Avalanches failing on a persistent weak layer can be very sensitive, and they might be triggered remotely, from a distance, or worse from below!
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Natural avalanches are possible today, and people are likely to trigger dangerous wind slab avalanches, 1 to 2 feet deep on steep upper and mid elevation slopes where drifts formed in the past week on weak, sugary, or faceted snow.
People should avoid travel in avalanche terrain today. 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.
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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