Avalanche forecast

Salt Lake

Issued Dec 27, 2019valid to Dec 28, 2019Utah Avalanche Center

Avalanche danger

Alpine
Treeline
Below treeline

Out of date — this forecast expired 7 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A MODERATE DANGER remains for human triggered sluffs and new snow avalanches on all upper elevation aspects and northwest through east-facing slopes at mid-elevations.

An isolated MODERATE DANGER ALSO EXISTS for triggering an avalanche 2-5' deep on northwest through east facing aspects. Continue to avoid steep rocky terrain as well as shallow slopes that have already avalanched this season.

The Fine Print - If the winds pick up earlier than expected OR we see more sun than forecast, the new snow will be more sensitive in steeper terrain .

Avalanche problems

Storm Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Possible
Size
2
Human triggered point release and new snow avalanches remain possible on all aspects at upper elevations and northwest through east-facing aspects at mid-elevations. With a wide variety of surface conditions before this most recent storm, these avalanches have a variety of weak interfaces to break on. This new snow instability will be most suspect on upper elevation and north-facing terrain that has been preserved by the cool temps and lack of winds.

The Fine Print:

If winds increase into the afternoon, at the uppermost elevations shallow soft slabs of wind drifted snow could begin to form. Look for signs of wind loading and avoid that terrain.

If we see more sun than expected, the new storm snow will become more active on the steepest sunlit slopes.

These slides are most problematic in steep, sustain terrain where the point release or sluff and new snow avalanche debris may pile up deeply or above-exposed rocky terrain that being knocked off your feet isn't an option.

There's generally little mystery with these types of avalanches: they break at your feet or sled and respond to cornice drops and ski cuts. Keep an eye on your partners; carry and know how to use your rescue gear.

Danger Trend: Steady to Decreasing
Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Unlikely
Size
3
We still have a potentially unstable snow structure of a strong slab over a very persistent weak layer of faceted snow near the ground on mid and upper elevation northwest through east facing terrain.

Overall this layer continues to present itself as dormant, giving no signs of avalanche activity for over a week, but it is not gone nor is it forgotten. Recent wind and snow has added a touch more stress to these basal weaknesses, but in isolated areas. While we are getting closer to seeing the absolute dormancy of this layer, we need more time.

Yesterday Mark and I targeted the Shale Shot area off the Park City Ridgeline where we found obvious facets at the ground and we were able to get propagation only with very hard hits of our shovel. This area best represents the most suspect slopes for this persistent weak layer, very rocky places or places with a thin snowpack (less than a ski pole in depth). While out traveling look for signs of a shallow snowpack by probing the depth with your ski pole or probe.

If you choose to enter the terrain where this avalanche problem exists, look at the terrain below you and consider the consequences of triggering one of these large avalanches.

Below is a photo representing the soft and shallow snowpack on top of the weak facets on the ground found in more suspect terrain. PC: Champion

Danger Trend: Steady to Decreasing

When will this layer go away?

Info about this layer and where it exists

Special Announcement

New blog post-Landmines - With permission, we are reprinting a recent piece of correspondence from an Army officer who is frequently deployed to the middle east. Drew spent time in the middle east as a naval intelligence officer in Desert Storm in the early 90s.

New podcast - Risk, Reward, and the Big Lie - A Conversation with Ski Guide Doug Workman

Jenna Malone's UAC Podcast - Betting Your Life - Why Forecasting is Poker and Not Chess - A Conversation with Jenna Malone - now has her video presentation from this fall's USAW.

Thanks to the generous support of our Utah ski resorts and Ski Utah, we have discount lift tickets available. All proceeds from these go towards paying for avalanche forecasting and education! Get your tickets here.

Recent Activity

Yesterday there were a few reports of sluffing on very steep slopes, above 40 degrees both in the backcountry and in the resorts. Across the board, these sluffs were generally running in the old-snow interface on a bed surface comprised of temperature crusts and wind old slabs. The photo below shows a ski cut on a 45-degree rollover which resulted in a sluff moving downhill and depositing 60-90 cms (2-3') of snow on the uphill side of trees. See the whole observation HERE which goes into a greater discussion on ski cutting and terrain choice.

Ski cut debris on a steep slope. PC- G. Gagne

Yesterday there was one report of a cohesive soft slab avalanche on the northeast facing terrain of LSB, likely triggered in the morning. There was a crown (estimted 6-10" deep and 75' wide) and it ran 60 feet. See full observation HERE. Wednesday a snowboarder yesterday unintentionally trigger a storm slab in Dutch Draw roughly a foot deep and 150' wide. Yes, that Dutch Draw, the site of the fatality on the 15th and wingsuit skier triggered avalanche a couple of days later. This avalanche was on east-northeast facing terrain at 10,000'. See the video below and full avalanche observation HERE.

LSB soft slab avalanche on a NE Aspect - PC. M. White

Snow and Weather

This morning trailhead temperatures are in the mid teens F, and ridgetop temperatures are in the low teens F. South to southeasterly are light, averaging in the mid-teens mph with a few gusts near 20 mph.

Since yesterday morning, the mountains picked up another 1-2" of snow bringing storm totals to 12-16" of snow in the upper Cottonwoods and about 10-12" of snow along the Park City ridgeline.

Today, temperatures should be cool in the upper teens and low20s F. The winds will remain calm and skies will be overcast into the afternoon. This evening winds should increase from the north northwest and bring a few scattered showers into Saturday morning. Skiing and riding conditions are excellent on all aspects and elevations but for some slight sun/greenhousing damage on some steep southerly aspects yesterday.

Our Week in Review - summarizing the significant weather and avalanche events of the past week - can be found HERE.

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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