Forecast: Salt Lake Area Mountains - Utah Avalanche Center

Forecast for the Salt Lake Area Mountains

Issued by Nikki Champion on
Saturday morning, December 26, 2020

There is a CONSIDERABLE avalanche danger at mid and upper elevations on aspects facing west, north, and east for triggering large avalanches that are 1-2' deep and up to several hundred feet wide. Avalanches may be triggered remotely and from lower-angled terrain. Avoid being on, underneath, or adjacent to slopes greater than 30°in steepness on these mid and upper elevation aspects.

On upper elevation southerly aspects, there is a MODERATE danger.

Mid elevation southerly aspects and low elevations have a LOW danger.

Low

Moderate

Considerable

High

Extreme

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Weather and Snow

This Morning: There are partly cloudy skies and a temperature inversion with lower-elevation trailheads in the teens and low 20's F and the upper 20's F along upper elevation ridges and peaks. Winds are out of the west/southwest and in the teens at mid-elevations, gusting into the upper 20s mph. At upper elevations, the wind speeds are averaging near 30 mph with gusts above 40 mph.

For Today: A fast-moving system crossing Northern Utah will push a cold front through our area, bringing colder temperatures, some precipitation, and increased winds. While precipitation rates will never get very high, starting around 9 am we can expect 1-3" of new snow by this evening. This snow will continue into tomorrow morning, bringing the final snow total closer to 3-6". Temperatures will rise to the upper 20s and low 30s F by mid-morning and then begin dropping throughout the day. Southwesterly winds will increase throughout the day, with gusts up to 25 mph at mid-elevations. At upper elevations, averages will be 25-35 mph with gusts up to 60 mph.

Next Storm: Looking further ahead, chances for light snow early this coming week and then perhaps right around the New Year.

Recent Avalanches

Week in Review: It has been active this past week, with snowfall, wind and over 30 natural and human-triggered avalanches reported. Catch up by reading our Week in Review - where we highlight significant snow and weather events from the past week.

Reports of remotely and sympathetically-triggered avalanches continue to roll in:

Thursday 12/24 - West Monitor on Park City Ridgeline. Control work from Park City resorts triggered slides up to 500' wide and 1-2' deep. In Days Fork a remotely-triggered avalanche at the top of Banana Days which then sympathetically pulled out two avalanches in adjacent Main Days. [Photos B. Nalli]

Friday 12/25 - Red Rocks Chute on Park City Ridgeline. Remotely-triggered soft slab on the persistent weak layer of facets. This avalanche was 60' wide and 14" deep.

This heat map shows the distribution of avalanches in the Salt Lake mountains since Thursday, December 17. They have been on aspects facing northwest through east - focused on northeast and east - above 9000'.

Type

Location

Likelihood

Size

Description

A persistent weak layer (PWL) of faceted snow and depth hoar exists in the bottom foot of the snowpack on mid and upper-elevation slopes primarily facing west, north and east. Snowfall and wind-drifted snow this past week have overloaded these weak layers, with several remotely-triggered avalanches. Today's increased winds and snowfall will only continue to add load and stress to this snowpack. Thursday's remote slide in Banana Days and then sympathetically-released slide in adjacent Main Days illustrates how strong and connected the slab on top of the PWL has become.

These recent avalanches - as well as continued loud, booming collapses and cracking - are huge red flags, telling us that the weak snowpack structure still exists and needs more time.

Photo from Mill-B South demonstrating the widespread cracking, this is a big red flag. Pay attention to what the snowpack is trying to tell us. (Photo: W. Thomas)

Avoid slopes steeper than 30° on mid and upper elevation aspects facing west, through north, and east. Triggering an avalanche on these slopes is likely; they may be up to 2' deep and several hundred feet wide.

Type

Location

Likelihood

Size

Description

Winds will be increasing throughout the day and into the evening, gusting up to 60 mph at 11,000 ft. The combination of any lingering soft snow and a few new inches of snow throughout the day will allow for new wind drifts to form at upper elevations. Today these drifts will be most widespread on the north through east-facing slopes, especially at the highest most elevations. However, as always with strong winds I would expect to find sensitive slabs of wind drifted snow on all upper elevation aspects, especially along with terrain features such as ridgelines, sub ridges, and gullies.

Triggering an avalanche that initially fails in the wind-drifted snow will likely break down more deeply into the weak faceted snow below. Today continue to look for slopes with any signs of wind drifted snow, such as cracking, hollow noises, and pillow-shaped snow, and avoiding those slopes.

Additional Information

Looking into the future: Mark Staples describes a new weak layer forming on sunny slopes. Over the next few days, this new weak layer could be buried by a few inches of snow and preserve. If we get a lot of wind, or warm temperatures this layer could be melted or blown away. Time will tell if it survives and gets buried. If that happens, then it could cause avalanches in the future. For now, we’ll have to watch it. Either way, this faceting happens from a very delicate balance of radiation at the snow surface.

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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.

Observations and Avalanches

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