Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

Overnight snow totals are in the 3.5 to 5-inch range for the SE Mountains. That snow combined with southwesterly winds overnight to form fresh wind slabs on the lee side ridgelines and cross-loaded terrain features.  In wind-sheltered areas, you can expect to encounter more of a loose snow avalanche problem. Take time to investigate these avalanche problems today, and make a plan to manage them in the terrain you want to ride. There remains a possibility of triggering an avalanche that breaks deeply into the snowpack. The most suspect areas for those persistent slabs would be areas with a weaker-than-average snowpack or some northwesterly wind-exposed terrain. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    In the Southeast Mountains, the last round of persistent slab avalanches occurred on March 16th. The most prominent weak layers are surface hoar buried a couple of feet deep and depth hoar near the ground. After another week of mild weather and no recent loading events, this avalanche problem has continued to slowly become less reactive in the big picture. Poor snowpack structure still exists in some areas and is commonly associated with a total snowpack height between 80 and 170cm. Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.   Triggered slab avalanches are unlikely on southerly aspects, or areas where the snowpack is consistently deeper than 200 cm.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem.

    A large persistent slab on Mt. Crested Butte that ran on 3/16.  This slope is shallow, variable in depth, and on the north half of the compass: a combination of ingredients you want to avoid.  

  • Wind Slabs

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

    Last night, the Cinnamon Mtn weather station at 12,000ft recorded southerly winds in the 20 to 30mph range with gusts in the 40's and 50's. While other weather stations recorded notably lighter wind speeds. Forecasted winds eventually become light and back to the west and northwest today. Fresh wind slabs have formed on the lee sides of ridgelines and cross-loaded terrain features. Plan to either avoid wind-loaded terrain today or investigate how reactive and large those slabs are before committing to wind-loaded terrain. 

    Example of a wind slab that formed in a cross-loaded gully.

Avalanche Discussion

Here are the 5am Snow Totals:

NW Mountains: Schofield Pass 7" snow and .6 to .9 SWE. Elkton ~5" snow. Irwin ~4" snow and .4 SWE.  

SE Mountains: Brush Creek 11,000ft 5" snow. CBMR 3.5" snow and .3 to .4 SWE. Upper Taylor 5" snow and .5 SWE.

The most likely to encounter avalanche problems today will be fresh wind slabs. Given the current amount of snow and decreasing wind speeds today, most of those wind slabs will be small in size. The Ruby Range and areas with a big fetch of snow avalible for transport, could be holding large wind slabs. These slabs have formed over crusts and some small facets on northerly-facing slopes. Forecasted winds pick back up into the 20's from the NW to N, later this afternoon and overnight with more snow in the forecast. 

The last persistent slab avalanches were observed on March 8th in the Northwest Mountains, and more recently on March 16th in the SE Mountains. Concerns for additional persistent slab avalanches have mostly been for areas with a relatively shallow snowpack where persistent weak layers have remained more pronounced. The persistent slab problem rose was trimmed to cut out areas that have seen recent meltwater draining into the snowpack, and now those old snow surfaces have started to refreeze. Both forecast areas made it through the last week of warm weather without any slab avalanche activity. It would have been nice to see some cornices fall and test some slopes, but we weren't so lucky. The problem rose now covers northerly facing slopes at near and above treeline elevations. Many below treeline slopes formed crusts or saw water running deep into the snowpack. Isolated exceptions would include a few due north to northwest facing slopes at lower elevations. The most suspect slopes are likely northwest-facing above 11,000ft, as those areas will more commonly have a shallower total snowpack height and more pronounced weak layers.

Regioni coperte