Bollettino valanghe

Salt Lake

Pubblicato il Feb 19, 2024valido fino al Feb 20, 2024Utah Avalanche Center

Pericolo valanghe

Alta quota
Limite del bosco
Sotto il limite del bosco

Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The avalanche danger is CONSIDERABLE at upper elevations where it may be possible to trigger a wind-drifted snow avalanche near ridgetops and on the leeward side of terrain features. Mid-elevation slopes have a MODERATE danger where we have had reports of avalanches failing on a new/old snow interface that was buried on Valentine's Day. This storm interface has been associated with a crust in many locations and we have seen avalanches failing 1'-2' deep on west-south-southeast aspects. This avalanche problem is spotty-meaning that a snowpit in one location may not tell you if the slope you want to travel on has this buried layer. Dig on slopes you wish to travel on to determine if this interface is present.

Sunny skies and filtered clouds could warm the snow surface particularly at lower elevations out of the wind zone, where you could see wet loose avalanche activity on the snow surface. Careful snowpack evaluation, cautious route-finding, and conservative decision-making will be essential today and if in doubt choose terrain less than 30 ° in steepness.

Problemi valanghivi

Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Likely
Dimensione
2
As winds increase throughout the day expect to see sensitive slabs of wind-drifted snow on all upper-elevation and mid-elevation terrain features. These drifts could be 6-24 inches deep and up to 150 feet wide. Watch out for signs of wind-drifted snow, such as pillow-shaped deposits, and avoid those slopes. Cornices are a sign of wind-loading. Watch for traffic below you before tickling any fresh cornices and be careful as they could break further back than you expect.
Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Unlikely
Dimensione
3
The early season persistent weak layer (PWL) avalanche problem is moving in the right direction as more snow is added to the snowpack, and this weak layer near the ground continues to gain strength. The last hard slab avalanche reported on this layer was February 15th on a northwest facing slope at 10,500' that most likely loaded from the southerly wind event. If an avalanche were to be triggered in the PWL, it would be 4-6 feet deep and well over a hundred feet wide. The Valentine's Day storm buried facets, weak stellar crystals, and surface hoar on many slopes. On Friday, Drew went to 10,420' to investigate this layer and yesterday I went and looked at an avalanche reported from Saturday on Davenport Hill. On east-facing slopes, collapsing was apparent, mainly due to facets, broken stellars, and small-diameter surface hoar associated with a buried melt-freeze crust.

Overwhelming avalanche activity on Saturday, let us know that southeasterly and easterly facing terrain is the current bulls-eye terrain for this issue. Due to this weak interface, remote triggering an avalanche from a distance remains possible.
Loose Wet
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Possible
Dimensione
2
Warm temperatures and sunny skies this morning will increase the likelihood of seeing wet loose avalanches entraining the newest storm snow. This will be more likely in locations out of the wind zone. If you start to see snow falling off of rocks or loose wet snow on steep terrain it's time to move to colder snow. Many roofs in mountain neighborhoods are still capped with storm snow and we may see some of these roof lines shedding this snow today. Keep an eye out for children playing or adults working around the house as they may be impacted by snow sliding off of roofs.

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Recent Activity

Yesterday we had reports of wind-drifted snow avalanches near ridgelines and soft slab avalanches within the newest snow on steeper terrain. Late yesterday afternoon a party was involved in an avalanche on the Petticoat above the Alta Summer Road. This avalanche was 2' deep and ran 250' vertical running on small grained facets on top of a melt-freeze crust. We had a report of a skier triggered wind-drifted snow avalanche in Rocky Point that was 2.5' deep and ran 300' vertical feet, and a report of an avalanche in one of the Wolverine Chutes 75' wide running the full length of the chute. Any of these avalanches would have been deep enough to bury a backcountry traveler. This was a busy weekend in the backcountry, with over 25 avalanches reported in the Salt Lake, Ogden, and Provo area mountains since Friday. Many of these avalanches failed at the interface with the old snow surface. Some of these areas have a firm melt-freeze crust with small faceted grains at the interface between the new and old snow. The stubborn and unpredictable nature of these avalanches is shown in the video below of the third skier on the slope triggering an avalanche off of the Park City ridgeline.

Video of the Conehead Avalanche off the Park City Ridgeline, 10,000' - SE Aspect- M. Fischer

Snow and Weather

This morning, under clear skies trailhead temperatures are in the 20's° F and the highest ridgelines are in the high teens °F. Winds are blowing from the southwest 15 gusting to 20 MPH at the lower ridgelines and from the west 20 gusting to 35 MPH at the 11,000' ridgelines. Last night's storm cleared out with one final burst of snow for most of the forecast region with accumulations of 5"-12" of snowfall and .4"-.75" of water. Yesterday there were reports of great travel on all aspects.

Today, will start out with clear skies, mild temperatures 36°-41° F and winds blowing from the south-southwest 25 gusting to 30 MPH at the 9,000' ridgelines and 30 gusting to 45 MPH at the 11,000' ridgelines. Clouds will increase this afternoon as wind speeds ramp up and we can look for 1"-3" of new snow and .10"-.25" of water by late afternoon. As the sun moves out and the clouds move in you may experience some green-housing on all aspects and elevations which could lead to wet loose avalanches.

Our partners at the National Weather Service have issued a Winter Weather Advisory from 5pm this afternoon through 10pm Wednesday night. Read more 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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