Avalanche forecast

Salt Lake

Issued Dec 28, 2022valid to Dec 29, 2022Utah Avalanche Center

Avalanche danger

Alpine
Treeline
Below treeline

Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The avalanche danger will continue to rise to HIGH on all upper elevation aspects and mid-elevation aspects facing northwest through north and southeast, where strong winds and continued snowfall have created dangerous avalanche conditions. Mid-elevation slopes facing west, southwest, and south have a CONSIDERABLE danger. Any avalanche triggered within the new snow or the wind-drifted snow has the potential to step down into deeper weak layers in the snowpack, creating a very large and dangerous avalanche.

The avalanche danger is MODERATE on low-elevation slopes that received primarily rain over the last 24 hours.

Traveling on, underneath, or adjacent to slopes steeper than 30° at the mid and upper elevations is not recommended. Avalanche conditions will remain dangerous through the weekend with continued stormy weather.

Avalanche problems

Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Likely
Size
3
Most avalanche activity on this persistent weak layer has been on northerly-facing terrain. This layer DOES exist at other aspects and elevations and it could begin producing avalanches when it gets loaded by heavy snowfall and strong winds.

The areas with the most uncertainty, and therefore highest level of concern for me are areas that have a generally substantial snowpack but have still been showing signs of propagation before this storm. These slopes will hold more water weight before they avalanche much wider and deeper. These will be unsurvivable avalanches. The uncertainty lies in the overall snowfall, water totals and how quickly we overload the snowpack. I am uncertain if this first system will overload the faceted grains enough to hit their tipping point, and for new snow and wind-drifted snow avalanches to begin stepping down deeper into this layer - but as we continue to add more snow and more wind, we do know that the likelihood of this happening will only continues to increase.

Today, I'd stay off of and out from under slopes over 30 degrees as the current snowpack adapts to the new snow and wind.
Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Likely
Size
2
With high wind speeds and soft snow available for transport you are likely to find sensitive slabs of wind-drifted snow on all upper-elevation slopes, and mid-elevation terrain features that allow for drifting snow to accumulate. The new soft slabs will be most pronounced on lee-ward facing slopes, but with such high winds can load any aspect because winds swirl and change direction as they pass through the mountains, this is known as cross-loading.

What to do? Look for evidence of fresh drifts and wind slabs that look wavy, rounded, smooth, and pillow, and avoid steep terrain where you could trigger them. Any wind slab avalanche that you trigger has the potential to step down into deeper weak layers in the snowpack.
Storm Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Likely
Size
2
Storm totals of 6-20" of new snow over the past 24 hours will create sensitive soft slabs of new snow on all aspects at mid and upper elevations. Periods of heavier precipitation are possible today, with peak periods of up to 2" of snow an hour. Expect the new snow to be sensitive during any period of higher precipitation intensity and watch for changing conditions. Lower elevations have primarily received rain over the last 24 hours and will have likely frozen with the drop in temperatures. Continue to pay attention though, if traveling through this lower elevation rain-soaked terrain I would avoid any location that has not to experience a true freeze, and one could sink through the entire snowpack to the ground. This could be a heads-up that wet avalanches could still occur at these elevations.

Special Announcement

Check out this great blog post that Dave put together discussing the persistent weak layer, and the forecaster's current mindset while dealing with it. You can read the full post HERE.

Recent Activity

No new avalanches were reported in the backcountry yesterday. Remote sensors picked up some natural activity during the early morning hours in the steep terrain of Little Cottonwood Canyon.

Snow and Weather

This morning, skies are overcast and snow continues to fall across the range. Temperatures are in the upper teens and low 20s F. Westerly winds have backed off overnight, currently blowing in the mid-20s with gusts up to 50 mph at the highest ridgelines. Snowfall totals range from 6-20" of new snow with 0.8-2.15" of water. Current snowfall totals are favoring the Park City Ridgeline, and Upper Big Cottonwood.

Today, an additional 3-7" of snow will fall with up to 0.5" of water by 5 PM. Snowfall could still be heavy at times, with peak periods up to 2" of snowfall an hour. Temperatures will be in the mid-20s F. Winds will continue to decrease throughout the day, and into the evening. Mid-elevation winds will blow from the northwest averaging 5-15 mph with gusts up to 25 mph and at the 11,000' ridgelines winds will average 10-20 mph gusting to 45 mph.

This is just the first in a series of three storms that are moving through Utah over the next week. After a break in the storms tomorrow, the next system should begin moving through the area on Friday slated to bring another 28-44" of snow to the area, and another 2.5-4.0" of water.

Additional Info

Check out this weather discussion that Mark and I had talking about the forecast today, and areas of certainty versus uncertainty within the snowpack.

General Announcements

Help support the UAC while doing your Holiday Shopping. The UAC's Holiday Silent Auction opens at 8:00 AM MT on December 26 and will close at 8:00 PM MT on January 2. Take a look at items and bid HERE.

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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

Backcountry Emergency Procedures