Lawinenlagebericht

Gunnison

Crested Butte Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Open full map
Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Snowfall and westerly winds formed stiff slabs of drifted snow on leeward terrain that may remain sensitive to the weight of a person.  These slabs will be harder to visually identify today as an inch or two of snowfall overnight has obscured previous surface textures.  Expect to find wind-drifted slabs below ridge tops, underneath cornices, and tucked behind terrain breaks or in cross-loaded gullies.  You can find safer terrain options in sheltered areas where winds are less likely to have formed slabs.  Very steep sheltered terrain can produce small loose avalanches that could pose a threat if you are carried into rocks or trees.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    New snow combined with strong southwest to west winds has created stiff Wind Slabs. In many areas, these slabs will be small in size, but in snow favored areas of the Ruby Range and the northern Elk Mountains, these slabs could become 14 to 20 inches thick and large in size. This avalanche problem will be the most widespread on the lee sides of ridgelines and cross-loaded terrain features at near and above treeline elevations. This avalanche problem will be less common at below treeline elevations and exist on a few cross-loaded terrain features. A wind slab is classically represented by a rounded or lens-shaped snow deposit, where additional snow has accumulated on the lee side of the terrain feature.  Shooting cracks, active snow transport, and fresh cornice formation all point to Wind Slab formation.

    4/13 - A small triggered Wind Slab from Wednesday below a roll in a near treeline basin.  Expect big, leeward slopes in the alpine to be capable of producing much larger avalanches than pictured here.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1.5–2

     Slab avalanches breaking into old weak layers several feet deep have become unlikely, but not impossible.  Higher elevation, northerly facing terrain still holds a dry, winterlike snowpack; thus we can't completely eliminate the potential for a rare but large slab avalanche on these aspects.  The most suspect terrain is where snow coverage is shallower,  especially on convex, unsupported slopes or near rock bands. You are most likely to trigger a slide from a shallower spot on the slope.  If you are skiing or riding in that type of terrain, reduce your group's exposure during uphill travel and choose appropriate safe zones from a large avalanche while descending.  Let your friend wrestle their stuck snowmobile off of suspect slopes by themselves.  A recent very large avalanche near Snowmass (observed 4/14) keeps this unlikely problem lingering in the minds of forecasters.

    Example of our most recent persistent slab avalanche that likely failed around March 30th.  This large avalanche highlights the type of terrain that remains most worrisome:  northerly, rocky, and unsupported.  

Avalanche Discussion

The greatest hazard today comes from wind-drifted slabs that formed over the past week.  Areas in the Northwest Mountains received the most snowfall this week and thus have the largest potential avalanches but consistent west to southwest winds were an equal opportunity for both the Southeast and Northwest Mountains.  Expect to find a similar distribution for Wind Slabs in both forecast zones but a slight increase in size in the Northwest Mountains.

The avalanche danger rating dropped to MODERATE (level 2 of 5) above treeline today.  This is due to a decrease in sensitivity to the Wind Slab avalanche problem.  On Wednesday, CBAC staff noted that it was easy to find signs of instability and trigger avalanches on drifted terrain features, and yesterday, signs of instability decreased and snow surfaces felt much stiffer than Wednesday.  Overnight an inch or two of new snow has obscured some of the evidence of the previous wind-loading making it a bit harder for you to visually identify the suspect slabs.  There is clear evidence of stronger snow above softer snow in drifted terrain features so appropriate travel advice suggests avoidance as the safest strategy.  Continue to treat upper elevation leeward terrain as suspect, and do not expect to see signs of instability before you potentially trigger a Wind Slab.

Sheltered terrain offers 'safer' avalanche conditions due to a lack of slab formation in the recent storm snow.  However, you can still trigger small loose avalanches on very steep sheltered slopes and the few inches of new snow overnight will add a bit more volume for loose avalanches to entrain.  Yesterday a skier was caught in a 'sluff' while descending a very steep sheltered slope on Schuylkill Ridge, but thankfully walked away without injury.  Even though the danger is LOW at low elevations, small loose avalanches remain possible on very steep terrain around 40 degrees or more.  Consider using ski cuts and traveling across the fall line to reduce the chances of getting caught up in a small loose avalanche.

Abgedeckte Regionen