Forecast: Salt Lake Area Mountains - Utah Avalanche Center

Forecast for the Salt Lake Area Mountains

Issued by Greg Gagne on
Wednesday morning, December 25, 2019

A MODERATE danger exists for triggering an avalanche 2-5' deep on northwest, through north, and east aspects. The slopes that are most suspect include steep rocky terrain as well as repeater slopes that have already avalanched this season.

Other terrain generally has a Low hazard, but an isolated MODERATE hazard exists at the upper elevations, and mid-elevation aspects facing northwest through east for triggering isolated pockets of sensitive wind drifts as well as shallow sluffs in loose storm snow.

Low

Moderate

Considerable

High

Extreme

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Brighton Resort is closed to uphill traffic over the holiday period through January 1.

Weather and Snow

Currently: Mountain temperatures are in the upper teens and low 20's F. Winds have diminished significantly since Tuesday afternoon. They are out of the west/northwest and very light, gusting < 10 mph. Overnight snowfall totals range from 2-4", with 24-hour totals from 3-6"

For today, you can expect periods of light snow showers with another 2-4" expected during the day. Winds will be westerly and remain light, < 10 mph with gusts in the teens at the upper-most elevation ridgelines.

Recent Avalanches

We received one observation from the backcountry on Tuesday, where a party reported cracking in wind-drifted snow.

Ski patrollers reported a few isolated wind slabs popping out with ski cuts and sluffing in the loose storm snow. (My Instagram feed indicated the small amounts of dense new snow greatly improved riding conditions.)

Type

Location

Likelihood

Size

Description

A dangerous structure of a strong slab of snow over a persistent weak layer of faceted snow down near the ground exists on mid and upper elevation aspects facing northwest, through north, and east. Although this weak layer has become mostly dormant over the past week, several days of southerly winds over this past weekend and through Tuesday have created dense wind slabs on the aspects where this weak layer can be found.

The most recent avalanche activity I am aware of that failed on this layer of weak snow down near the ground occurred overnight Saturday in South Monitor bowl along the Park City ridgeline (observation). This slope has avalanched this season (known as a "repeater"), with weak faceted snow remaining in place on the bed surface. The slope had filled in again from wind-loading, and naturally avalanched, perhaps from a cornice fall.

Although the likelihood of triggering one of these large avalanches reduces each day, there remains a possibility. Slopes that have a thinner and weaker snowpack are the most susceptible, this includes:

- steep rocky terrain;

- repeater slopes that have already avalanched this season (i.e. South Monitor).

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

Danger Trend: Steady to Decreasing

When will this layer go away?

Info about this layer and where it exists

Type

Location

Likelihood

Size

Description

You may find isolated pockets of recent wind-drifted snow on all aspects at the upper elevations, and at the mid-elevations on slopes facing northwest through east. Watch for signs of sensitive wind drifts such as cracking, as shown in the photo below (A & B photo) taken yesterday on a northerly aspect in Cardiff Fork:

In addition, you may find isolated pockets of sensitive storm snow and shallow, long-running sluffs in the loose snow on steeper terrain.

Danger Trend: Decreasing

Additional Information

In Monday's forecast, Trent described using a propagation saw test (PST) to assess the propagation propensity of a weak layer with a slab on top. For those wishing to learn more about this test, I encourage you to look at Monday's archived forecast for more detail.

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.

Observations and Avalanches

Backcountry Emergency Procedures