Bollettino valanghe

Salt Lake

Pubblicato il Dec 14, 2020valido fino al Dec 15, 2020Utah Avalanche Center

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Pericolo valanghe

Alta quota
Limite del bosco
Sotto il limite del bosco

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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Approach any steep wind drifted slope with extreme caution.

Areas of CONSIDERABLE danger exist on many slopes at the mid and upper elevations. The danger will be more pronounced on steep northwest to north to east facing slopes. Human triggered avalanches 12-18"+ deep are likely and may be triggered at a distance. They may also be triggered from below. Collapsing and cracking are immediate signs of an unstable snowpack.

Please make conservative decisions to avoid getting hurt and further stressing emergency services and the health care system.

Problemi valanghivi

Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Very Likely
Dimensione
2
I suspect that - owing to the increased southwest winds - that some avalanches ran naturally last night. Today, those same types of avalanches may be triggered by a skier or rider on or on approach to a steep wind drifted slope. Most slopes yesterday did not have a cohesive slab but today many do. I believe that the fresh wind drifts are now just the slabs that our previous weak layers have been waiting for. Collapsing and cracking are sure-giveaways to warn you away from steep terrain. Remember that these avalanches may be triggered from a distance or from below.

Problem: Nearly all aspects and elevations held very weak faceted sugar snow before the storm. The dangerous slopes will be the ones where winds have drifted snow into a cohesive slab. Unfortunately, many of the tell-tale signs of drifts (rounded, chalky, etc) will be covered and hidden by the new low density snow.

Solution: Slope angle is the key. Stay off of and out from underneath slopes 35° and steeper. See UAC forecaster Toby Weed's video below.
Storm Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Possible
Dimensione
1
Sluffing in the steepest terrain is possible today with the additional snowfall. These will occur independent of aspect and may be enough to either gouge down into the older weak faceted snow or potentially trigger a fresh wind drift.

Recent Activity

The snowpack tipped its hand Saturday night into Sunday. And I suspect that some natural avalanches ran last night with the stronger southwest winds.

One observer yesterday noted a 10" deep and 50' wide natural soft slab avalanche in steep east facing terrain of mid-Days Fork (a run known as Crystal Palace) of Big Cottonwood Canyon, elevation 10,000'.

Also, a skier was briefly caught and carried in a 12" deep and 35' wide avalanche that broke well above him on Sunset Peak (pic below). This avalanche is in steep north facing terrain at 10,500' in backcountry terrain between Alta and Brighton.

Snow and Weather

It's lightly snowing in the mountains and as of 4am, most areas have picked up a trace to 2". Temperatures are in the mid to upper teens.

It is the winds, however, that played the spoiler. The southwest winds picked up in the early evening with hourly averages of 25-35mph with gusts to 50mph. They're currently blowing 10-15mph as they continue to shift to the west and northwest.

For today, we'll see off and on snowfall that may add up to an additional 2-4" of low density snow.

Winds will be 10-15mph from the northwest; temperatures will be in the mid-teens up high, the low 20s down low.

Kelvin-Helmholtz waves above the Pfeifferhorn yesterday

We'll see partly cloudy skies tomorrow with a plume of moisture associated with a warm front Tuesday night into Wednesday. This should be primarily along the Idaho border however. The next storm system looks to arrive Thursday night.

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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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