Bollettino valanghe

Salt Lake

Pubblicato il Feb 17, 2020valido fino al Feb 18, 2020Utah Avalanche Center

Pericolo valanghe

Alta quota
Limite del bosco
Sotto il limite del bosco

Non aggiornato — questo bollettino è scaduto 7 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The avalanche danger is HIGH at all upper elevations and aspects for triggering soft slabs of both new snow and wind drifted snow. Avalanche conditions are very dangerous. Avalanches are likely and avalanche terrain should be avoided. At mid-elevations, human triggered avalanches are likely and the avalanche danger is CONSIDERABLE. At low elevations the danger is MODERATE.

Today with very dangerous avalanche conditions, avoid traveling on or below slopes steeper than 30 degrees.

Problemi valanghivi

Storm Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Very Likely
Dimensione
2
Since yesterday, up to 20 inches of new snow has fallen on a variety of bed surfaceson which it can avalanche. In many places the new snow will fracture on a layer of weak, faceted snow just above an ice crust that formed on February 7th. In other places, this layer of facets does not exist but the new snow has not yet bonded with the underlying crusts or other hard surfaces. These crusts and hard layers will allow avalanches today to run long distances today. Another factor making the new snow unstable is that warm temperatures during the storm yesterday allowed the new snow to form a more cohesive slab. With more snow overnight, these slabs have gotten thicker. Today avalanches to be larger, more cohesive and avalanches easier to trigger than they were yesterday.

Photo of a slope not steep enough to slide cracking in Porter Fork. This is an obvious sign of instability. (Photo: Mletschnig)
Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Likely
Dimensione
2
Overnight winds were strong. Westerly winds hit speeds of 80 mph and should continue to gust up 45 mph throughout the day. The increased westerly winds will be moving enough snow to continue creating fresh wind drifts at the mid and upper elevations, primarily on aspects facing East, but cross-loading is possible on any aspect. These slopes can be loaded from the top of ridges or across the sides of other ridges. 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.

Special Announcement

Discounted lift tickets - Thanks to the generous support of our Utah ski resorts and Ski Utah, all proceeds from these ticket sales go towards paying for avalanche forecasting and education! Get your tickets here.

Recent Activity

Natural avalanches are occurring. Early this morning, around 0200 a natural avalanche cycle occurred in Little Cottonwood Canyon with some avalanches hitting the road.

Yesterday, ski patrols triggered both shallow soft slabs and loose snow avalanches within the new snow using ski cuts and explosives.

In the backcountry, widespread cracking and avalanches were reported. The avalanches from yesterday include the following:

-Multiple avalanches on Reynolds Peak (Soft Slab - E - 9400’ - Skier Triggered), (Dry Loose- E - 9300’ - Skier Triggered)

-Emmas Ridge (Soft Slab - N - 10000’ - Snowboarder Triggered)

-Highway to Heaven (Soft Slab - E - 10200’ - Skier Triggered)

-Catchers Mitt (Soft Slab - E - 9400’ - Snowboarder Triggered)

-Big Water Gulch (Soft Slab - N - 8800’ - Skier Triggered)

-Flagstaff Ridge (Soft Slab - S - 9800’ - Snowboarder Triggered)

-Grizzly Gulch (Soft Slab - NW - Skier Triggered)

Confused about locations? Steve Achelis has a great map and web page and app. Wasatch Backcountry Skiing Map. Check it out.

Across the board, these new snow avalanches were shallow soft slabs, 5-8 inches deep. All of these avalanches were easy to trigger and ran far and fast.

Great photo of a soft slab avalanche that occurred on Reynolds yesterday. (Photo: M. White)

Snow and Weather

This morning, mountain temperatures are in the upper teens and low-20s F at trailheads, and low teens F at upper elevations. Winds have dropped off a bit, and are currently west-northwesterly and northwesterly averaging 5-15 mph with mid-elevation gusts of 30-35 mph and upper elevation gusts up to 50 mph. Last night upper elevations gusts hit over 80 mph. It is still lightly snowing.

24-hr storm totals are:

Little Cottonwood Canyon: 15-19” snow (1.50”-1.95” water)

Big Cottonwood Canyon: 12”-23” snow (0.90” - 1.90” water)

Park City Ridgeline: 12-15” snow (1.20” water)

Today, short periods of snow showers will continue and bring another 4-7 inches of snow before the evening. Mountain temperatures will be in the low to mid-20s F, and winds will continue to west-northwesterly and northwesterly, averaging 10-25 mph, with gusts of 25 to 45 at the highest ridgelines.

Additional Info

LOOKING BACK:

Before this storm cycle, 2-4” rested on top of 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. In some places a combination of warm daytime temperatures and sunshine healed this layer. In other places this layer survived and has been buried.

The problem with this layer is that many slopes will remain unstable and will easily produce avalanches. Other slopes that do not have this layer will stabilize much more quickly in coming days.

General Announcements

CLICK HERE FOR MORE GENERAL INFO AND FAQ

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