Bollettino valanghe

Provo

Pubblicato il Dec 24, 2020valido fino al Dec 25, 2020Utah Avalanche Center

Pericolo valanghe

Alta quota
Limite del bosco
Sotto il limite del bosco

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

In sintesi

Today there is a CONSIDERABLE avalanche danger at upper elevations. There is a persistent weak layer of old faceted snow underneath recent snow that will fracture and produce avalanches. There are also fresh slabs of wind drifted snow that will avalanche. The simple solution is to avoid avalanche terrain and ride slopes less than 30 degrees in steepness. At mid elevations, the avalanche danger is MODERATE.

Below 8,000', there is a LOW avalanche danger simply because there isn't enough snow.

Problemi valanghivi

Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Likely
Dimensione
2
A persistent weak layer (PWL) of faceted snow exists in the middle of the snowpack on most slopes except ones facing south and southwest. There is just barely enough of a slab of snow on top of this weak layer to create an avalanche. Becuase the snowpack is so thin, it will continue to facet and weaken. Avalnache activity in the SLC area mountains has been a good preview to what will happen with the Provo area snowpack when more snow comes.

The bottom line is that triggering an avalanche on this layer is likely, and I would avoid avalanche terrain today, tomorrow, the next day, and for weeks to come. What makes an avalanche dangerous is the trauma it would cause sweeping you over rocks and other obstacles that are not buried yet.

Video below describes layers in the Provo area snowpack.
Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Possible
Dimensione
2
Very strong winds blew Tuesday afternoon and evening (80 mph gusts at 11,000 ft). In many places yesterday, winds calmed and the new snow made it hard to see evidence of these winds. In other places winds continued transporting snow yesterday. This morning's uptick in northerly winds should keep transporting snow.

Freshly formed slabs of wind drifted snow should still be able to produce an avalanche today. They will also add weight and stress to a buried PWL (see discussion above) and cause avalanches to break wider and farther because winds are very good at forming stiff, cohesive slabs of snow.

Photo of winds transporting snow along the Park City ridgeline yesterday (G. Gagne).

Special Announcement

Thanks to the generous support of our local resorts, Ski Utah, and Backcountry, discount lift tickets are now available.

Support the UAC while you ski at the resorts this season. Tickets are available here.

Recent Activity

Yesterday in upper Dry Fork ski guides reported a remotely triggered avalanche by another party that was 2-3 feet deep and 150 feet wide on a ENE aspect near 10,000 feet (no photo).

Local ski areas triggered a few more slides that broke into old facets.

Many groups in the Salt Lake area mountains yesterday reported collapsing and cracking and suspect anyone riding in the Provo area mountains would have experienced the same.

Photo (J. Mletschnig) of a shooting crack in Cardiff Fork yesterday.

Snow and Weather

Tuesday's storm delivered 3 inches of snow (0.07-0.2 inches of water). Very strong winds blew Tuesday evening at the start of the storm and generally eased by yesterday morning although they were still transporting snow in some areas.

This morning temperatures are mostly in the low teens F with some trailhead temperatures in the single digits F. Ridgetop winds are blowing 10 mph and gusting 20 mph from the northwest.

Today will have clear sunny skies under a ridge of high pressure. Winds will slowly ease through the day and temperatures will warm to near or above freezing.

The snowpack is 12-18 inches deep. Snowfall Tuesday night helped riding conditions although an ice crust from warm temperatures and a rime event on Sunday can be found under the new snow. Expect the snow on south facing slopes to get a little damp this afternoon.

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