Bollettino valanghe

Ogden

Pubblicato il Dec 15, 2024valido fino al Dec 16, 2024Utah Avalanche Center

Pericolo valanghe

Alta quota
Limite del bosco
Sotto il limite del bosco

Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The avalanche danger is CONSIDERABLE on upper-elevation slopes facing northwest, north, northeast, and east, where it's likely to trigger a persistent weak-layer avalanche. Here, avalanches may be triggered from a distance (remotely) and could be large enough to bury a human. We also have a MODERATE avalanche danger for both hard and soft slabs of wind-drifted snow across many aspects and elevations due to the strong wind.

Today, careful snowpack evaluation, cautious route-finding, and conservative decision-making will be essential.

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
On almost all shady slopes across the mid and upper elevations, we have weak and faceted snow (weak layer). Weak snow with heavier, more dense snow on top = avalanches.

Natural and human-triggered avalanches will remain likely today across the upper-elevation wind-loaded terrain. These avalanches could be 1-2 feet deep, up to 100 feet wide, and large enough to bury a human. Today, an avalanche can be triggered remotely, meaning from a distance. I would stick to terrain under 30 degrees in steepness with nothing above or adjacent to you that could avalanche.

Photo: Gagne & Brandt showing our slab over faceted snow.
Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Possible
Dimensione
2
Yesterday's and today's elevated wind will continue loading some slopes while stripping others. In any case, be on the lookout for wind-drifted terrain and avoid areas where the snow looks pillowy, rounded, or hollow like a drum. Today, you will be able to find both hard and soft slabs of wind-drifted snow on a variety of aspects and elevations.

If you trigger a wind-drifted snow avalanche, it's likely to fail within the storm snow or break deeper into faceted snow, making it much larger and more dangerous.

Photo: Gagne & Brandt showing wind drifting on Cutler Ridge.

Additional Info

Video: Greg showed us full propagation in an extended column test on Cutler Ridge yesterday.

Special Avalanche Bulletin

What: Heavy snowfall and drifting by strong winds will cause dangerous avalanche conditions to develop this weekend in the mountains of northern Utah.

When: In effect from 6 am MST this morning through 6 am Monday morning

Where: For the mountains of Northern Utah and Southeastern Idaho, including the Wasatch Range...Bear River Range... and Western Uinta Mountains.

Impacts: Dangerous avalanche conditions will develop on many slopes today. People are likely to trigger avalanches by being on or below slopes steeper than 30 degrees. Avalanches could be triggered remotely (from a distance) or from below.

What to do: Avoid traveling on or underneath steep north-facing terrain at mid and upper elevations in the backcountry. Carry and know how to use avalanche rescue equipment.

Recent Activity

During yesterday's peak winds, we likely saw a natural avalanche cycle within the storm snow. In some cases, with enough wind loading, avalanches broke into weaker faceted snow (pic below). Backcountry observers noted isolated shallow wind-drifted snow on ridgelines. They also noted cracking and collapsing within the snowpack. Snowpack tests showed propagation across the columns. See Gagne and Brandt observation HERE or the video below.

Photo: Van Silver showing a natural avalanche north of the Divide on the Ben Lomond ridgline.

Snow and Weather

Overnight, the headline continued to be the southerly wind, which wreaked havoc across the upper elevations, averaging 20 to 30 mph with gusts into the 40s and 50s.

This morning, it's beginning to snow (heavy in places). This brings the three-day storm total to roughly 6 to 12 inches of snow (0.34"-0.80" swe). It's tough to add up as all the snow was blown from the boards. Ben Lomond just had a reading of 0.40 inches of water in an hour. That's impressive, and if it's true, there is likely a natural avalanche cycle happening now at that location.

The wind has veered west and continues to blow 15 to 25 mph, with gusts into the 20s and 30s along the upper ridgelines. On Ogden Peak it's currently blowing 30-40 mph gusting to 52. Current mountain temperatures have cooled and range from 20 to 30 °F.

Today, we can expect snowfall in the morning hours, with hopefully 3 to 7 inches (0.20"-0.45" swe) of new snow throughout the day. Ben Lomond already beat this forecast. The wind will remain from the west and northwest, at times averaging 10-20 mph with gusts into the 20s and 30s. Mountain temperatures will remain cold as this storm ushers in colder air, with daytime highs topping out in the mid to upper 20s °F.

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