The avalanche danger is HIGH. Very dangerous avalanche conditions exist. Natural and human triggered avalanches are very likely.
Avoid all avalanche terrain. This includes underneath steep terrain. Avalanches will run fast and far today.
Moderate to strong winds from the west-northwest will also tip the scales. Natural and human triggered avalanches will again be very likely. Avoid all avalanche terrain. This includes being under avalanche paths.
CORNICES have grown unruly and may calve off naturally. These may then trigger larger avalanches on the steep slope below.
It's no secret or surprise: natural and human triggered avalanches are very likely in steep terrain of all aspects. Avoid all avalanche terrain. This includes being under avalanche paths.
***I am certain that we will see avalanches within the new snow and some of these avalanches will be large and long running. The great uncertainty lies in whether some of these avalanches will step down into older storm snow from the past week or two. Regardless, the travel advice is the same - Avoid being on or beneath steep terrain.
What
The avalanche danger for the warning area will be HIGH today.
When
In effect from 6am MST this morning to 6am MST Wednesday
Where
For the mountains of Northern Utah and Southeast Idaho including the Wasatch Range, Bear River Range, and Uinta Mountains..
Impacts
Recent heavy accumulations of snow and drifting have created widespread areas of unstable snow. Long running natural and human triggered avalanches are likely. People should avoid being in backcountry avalanche terrain, (off of and out from under slopes steeper than 30°), and stay clear of avalanche runouts.
Ski areas yesterday reported widespread and sensitive but shallow long running soft slab and loose snow avalanches. Long running natural avalanches ran in the early evening hours. Backcountry observers reported sensitive new snow soft slabs, even in protected terrain of the mid-elevations.
Check out all observations HERE.
It's the perfect storm.
Overnight snow totals in upper LCC are 20-24" (1.07-1.30" Snow Water Equivalent). Those are overnight snow totals. Storm totals are 35"/2.30".
Big Cottonwood - 8-16", favoring the mid-canyon. Storm totals are 20-24"/1.3"SWE.
Park City ridgeline - 6-12", favoring the north end of the ridgeline. Storm totals are 16-24"/1.17"SWE
Mountain temperatures are in the single digits to low teens.
Winds, as foretold, ramped up overnight from the west-northwest, blowing 15-25mph with gusts to 40. The highest peaks have gusts to 75.
We'll see continued periods of heavy snowfall today with perhaps an additional 6-12" or so, although amounts may vary widely. Snowfall will continue through tomorrow morning.
Mountain temps will be in the single digits to low teens. Winds from the west-northwest will lose some steam, but I view them as excellent wind slab building material.
We dry out mid to late week with a warming trend on tap for the weekend.
In the early 2000s, UDOT, Alta and Snowbird, the town of Alta, and UTA commissioned Chris Stethem and associates to conduct a formal study on the avalanche hazard in Little Cottonwood Canyon. Their paper can be found HERE.
The study relied on a methodology called the Avalanche Hazard Index (AHI) to understand the existing risk and evaluate alternatives. The AHI has several important variables that are calculated, including the frequency of the slides reaching the road, the quantity of paths along the corridor, and the volume and speed of traffic. These factors all contribute to the risk to vehicles along Little Cottonwood Canyon.
According to the AHI methodology, Little Cottonwood Canyon is one of the highest-risk roads in North America.
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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.
