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Forecast for the Salt Lake Area Mountains

Evelyn Lees
Issued by Evelyn Lees for
Saturday, December 8, 2018
The avalanche danger is CONSIDERABLE on upper elevation slopes facing northwest through easterly, where a slide could break 2 to 4 feet deep, failing near the ground on weak, sugary facets. On these same shady, mid elevation slopes and upper elevation westerly and southeasterly facing slopes, the avalanche danger is MODERATE. Here, the likelihood of triggering a slide is less, though it would still break near the ground.
In Utah, we can live and die by aspect, use a compass to precisely nail down the direction a slope faces.
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Weather and Snow
Mountain temperatures are in the 20s this morning, and southwesterly winds very light, averaging 5 to 10 mph at all elevations. Skies will remain mostly cloudy for the day, with a dusting of fresh snow possible as a weak disturbance moves by to the north. Winds across the highest ridge lines will increase, into the 15 to 25 mph range. The high pressure ridge moves in on Sunday, and by Monday, 9000’ temperatures will warm to near 40. The next chance for a shot of snow is around Wednesday.
Snow depths in the Cottonwoods are almost 4 feet at the upper elevations and 2 to 3 feet at the mid elevations and on the Park City side. Though the sunny slopes are all sun crusted, decent settled powder remains on the shady slopes.
Recent Avalanches
Yesterday, avalanches breaking on facets near the ground were released with explosives in Big and Little Cottonwood. They were on north through east facing slopes, between 10,000 and 10,500 feet. Yesterday and Thursday, there were continued reports of collapsing in the backcountry, including one on a west-facing slope at 9,000.
Check out the second Weekly Review by Greg Gagne, highlighting an active early week of snow and avalanches.
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Upper elevation slopes facing north and northeast remain the bull-eye terrain for harboring weak faceted snow, and are where dozens of avalanches have been triggered in the backcountry or at resorts. The faceted snow near the ground, and it formed when a shallow layer of October and pre-Thanksgiving snow sat around for weeks.
The pattern is more complex on the mid elevation shady slopes and on upper elevation NW, W, E and SE facing slopes, with some slopes lacking facets and others having large collapses and recent avalanches. If you want to go steep on these slopes, do some research - find a representative lower angle slope, get out your shove and dig down to the ground, looking for facets. Below is a great video by Quinn Graves and Bo Torrey showing unstable results on a northeast-facing slope at 8,500’, indicating stay off steep slopes of a similar aspect and elevation.
The past week’s avalanche roses illustrates how “persistent” or slow to strengthen the weak layer is.
Avalanche Problem #2
Normal Caution
Type
Location
Likelihood
Size
Description
Terrain without old faceted snow near the ground has a mostly low avalanche danger, but small avalanches can be triggered in isolated places – perhaps a newly formed wind drift along a high ridge line as the winds speeds increase today, or a sluff on a very steep, northerly facing slope. Terrain that’s super steep or has cliffs, trees or gullies below you has higher consequences if you are caught in even a small slide
General Announcements
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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.
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