Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A large, natural slab avalanche occurred yesterday on East Beckwith.  Heightened avalanche conditions exist where you find drifted snow on leeward terrain features.  Slab avalanches could break in the fresh drifts or deeper in the snowpack beneath older hard slabs.  Additionally, you can easily trigger loose avalanches on sheltered northerly-facing terrain.  Take a cautious approach if recreating in drifted terrain by reading loading patterns and making slope-specific judgments to avoid triggering a dangerous slab avalanche. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Strong northwesterly winds last week raked the mountains and mixed into typically more sheltered locations.  The incremental wind drifting built hard slabs ranging from just a few inches to several feet thick that is now buried and obscured by recent storm snow.  Although you can find these slabs at any elevation, we've seen the most significant wind loading and slab formation occurring nearing treeline, especially in terrain with large fetches favored by northwest winds.   These slabs are slower to heal because they formed above exceptionally weak facet layers.  They can also be remotely triggered from below or adjacent to steep slopes where the drifted snow spans onto lower slope angles.   The problem is localized to leeward terrain features behind tree fences, on the lee sides of ridged terrain features, and in concave catchments such as gullies.   Collapses and shooting cracks are clear warning signs of the problem.  Give wind-loaded terrain a wider berth than normal as surface clues have been buried by the recent storm snow: there have been several near misses this week with some slides breaking into lower-than-usual slope angles.

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Dry loose avalanches (sluffs) are a concern in wind-sheltered terrain on the north half of the compass.  Where the snow surface is weak and cohesionless, you can easily trigger sluffs that entrain the top 8" to 14" of loose snow on slopes steeper than 35 degrees.  The recent storm has increased the snow available for loose avalanches to entreain.  Ski cuts, moving across the fall-line while descending, or choosing lower-angled slopes are effective techniques to manage this problem. These point-release avalanches will accumulate more mass in long-running, steep terrain. Use caution above gullies where an avalanche can pile more deeply and above trees and cliffs where the consequences of getting caught in a sluff will be magnified. This problem is most common in sheltered terrain below treeline, but you can also trigger sluffs on some near treeline slopes and a few above treeline slopes.    

Avalanche Discussion

Wednesday's storm delivered 2 to 9 inches of snow.  The Northwest Mountains accumulated 4 to 9 inches with the highest totals in the Ruby Range.  The Southeast Mountains picked up 2 to 5 inches of storm snow.  Winds initially from the southwest then later the north/northwest redistributed the new snow to leeward terrain features forming a new round of slabs at the surface.  Your primary concern today should be to manage the new wind-drifted slabs and older, hard slabs stacked below.  A secondary concern is managing loose avalanches in sheltered terrain.

Wind Drifted Terrain:  Leeward terrain features will have formed fresh slabs at upper elevations that could be sensitive to the weight of a person.  Fresh wind-drifted slabs will be the largest and most concerning for areas that accumulated the most storm snow in the Northwest Mountains.  Finding more than about 7 inches of drifted snow is a good clue that you have found a potential Wind Slab.  Cracking or collapsing is a clear sign of instability that you should heed.  Keep in mind that there are older hard slabs (Persistent Slab problem) stacked beneath the recent storm snow.  Here are a few recent examples of Persistent Slab avalanches from Schuylkill Ridge, Wolverin Basin, and East Beckwith.  The details of the East Beckwith slide are hard to make out in the image, but the avalanche was clearly large enough to kill you.  Take the time to read through the Persistent Slab description above and watch the video to get a clearer picture of the necessary ingredients.  Make sure your primary goal today is to avoid triggering one of these dangerous hard slabs.

Sheltered Terrain:  You can be confident that steep, sheltered terrain facing the north half of the compass will produce loose avalanches.  The new storm snow has added a bit more volume for loose avalanches to entrain.  In general, these avalanches are not big enough to bury you outside of a terrain trap but could carry you into trees, rocks, or cliffs.  Ski cuts and moving across the fall line are simple techniques to prevent being taken for a ride. 

Regioni coperte