Forecast: Salt Lake Area Mountains - Utah Avalanche Center

Forecast for the Salt Lake Area Mountains

Issued by Nikki Champion on
Sunday morning, February 16, 2020

Today's new snow may produce soft slab avalanches or long running sluffs. Additionally, westerly winds may create unstable slabs of wind-drifted snow at upper elevations. This morning the overall avalanche danger is LOW rising to MODERATE as the storm develops, but it may spike to CONSIDERABLE during periods of heavy snowfall later this afternoon. Pay attention to changing weather patterns.

Human triggered avalanches are possible. Natural avalanches are unlikely, but possible during periods of heavy snowfall or stronger winds.

Low

Moderate

Considerable

High

Extreme

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Weather and Snow

This morning, mountain temperatures are in the low 30s F at trailheads, and low to mid-20s F at upper elevations. Winds are currently westerly averaging 15-25 mph with mid-elevation gusts of 30-35 mph and upper elevation gusts up to 65 mph. Snow has lightly begun to fall in places, with a trace amount of accumulation thus far.

Today, there will be a warm advection with what the national weather service is calling a “mean” westerly flow. This will bring warm mountain temperatures, in the mid-30s F, consistent light to moderate periods of dense snowfall, and westerly winds average 15-25 mph with gusts up to 65 mph at the highest ridgelines.

The strongest snowfall of the day will come this afternoon into the evening before the snowfall tapers off and cold air spreads into the area. The storm totals could bring us 10-16 inches of snow, and up to 1.25” inches of water by tomorrow.

Recent Avalanches

No new avalanches were reported from the backcountry.

Our Week in Review - where we highlight significant weather and avalanche events from this past week - is published HERE.

Type

Location

Likelihood

Size

Description

Dense snow has lightly begun to fall on a variety of supportable surfaces. These surfaces vary from the widespread February 7th rime/rain event crust (the “Dickens Crust”) to a weak layer of facets atop of a crust, to supportable wind drifted snow. The simple issue today is, as the snow intensity increases, this new snow is going to have a variety of excellent bed surfaces to slide on, and I expect to see shallow avalanches in the backcountry today.

With the warm temperatures, I expect the new snow to be fairly cohesive and should break as a shallow soft slab, but this may also include fast long-running sluffs, especially in the upper elevations. Watch for signs of instability such as cracking and sluffing.

Today, the sensitivity of the new snow largely depends on the rate of snowfall. During higher rates of snowfall (greater than 1 inch per hour) avalanches will be easier to trigger. Periods of snowfall exceeding 1 inch per hour are possible during the day today, especially this afternoon into the early evening. Pay attention to changing weather and increased snowfall rates.

Type

Location

Likelihood

Size

Description

The increased westerly winds may create fresh wind drifts at the mid and upper elevations, primarily on aspects facing East, but cross-loading is possible on any aspect. Look for obvious signs of wind-drifted snow, and avoid those slopes.

Additionally, these fresh wind drifts will increase the size of our cornices adorning many ridgelines, making them possibly even more sensitive. Stay well back from - and avoid travel below - corniced ridges.

Below is a photo of a large cornice that could be expected to grow today in Butler Fork (Photo: M. White)

Additional Information

LOOKING AHEAD:

Before this storm cycle, we had 2-4” of snow sitting atop a widespread rain/rime crust that formed late Friday, February 7th (The "Dickens Crust"? February 7 is Charles Dicken's birthday and this crust may prove to be the dickens!). The cold temperatures began to weaken, through a process called faceting, the snow both above this layer. While the issue today is primarily new snow instabilities, if we continue to add more snow (and water) in the form of a slab on top of this weak interface we could eventually have a persistent weak layer on our hands. For now the “Dickens Crust” just serves as an excellent bed surface for avalanches to run on, but continue to monitor this layer as we move into the upcoming weeks.

Below is a video of Jake Hutchinson talking about the weak snow interface on Mt. Aire. See full observation 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.

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