Boletín de aludes

Moab

Utah Avalanche Center
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Peligro de aludes

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The avalanche danger remains MODERATE today with several potential problems.

  • Wet Snow Without a freeze for several nights, sun-exposed slopes will become wet, sloppy, and susceptible to avalanches. Signs of instability include roller balls, pinwheels, and small point release sluffs. Stay off of and out from under steep slopes when these signs are present.
  • Persistent Weak Layer Deep and dangerous human-triggered avalanches failing on a layer of sugary, faceted snow remain possible primarily on steep slopes near and above treeline that face NW-N-E-SE. This is becoming a low probability/high consequence situation. Shallow areas along slope margins and near rock outcroppings or sparse trees are potential trigger points.
  • Wind Drifts Isolated, unstable wind drifts may exist on the leeward sides of ridge crests and terrain features in upper elevation, wind exposed terrain. Avoid steep wind drifted slopes.

Problemas de aludes

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2

    Overnight temps remained warm and it barely froze at 10,000', making this the third night in a row without refreezing. As the day heats up, so will the likelihood for wet avalanches, especially human triggered. The most dangerous slopes include steep terrain on southerly and westerly aspects in the afternoon, especially in lower elevations and wind-sheltered areas. Best practice is to stay off of steep slopes that are unsupportable, especially if they are wet and sloppy.

    The surface of the snow may be hiding wet snow underneath. Take time to dig down and investigate whether the underlying snow is wet or moist. On southerly aspects with strong melt-freeze crusts, water could percolate down until reaching an impermeable layer and produce a wet slab avalanche.

    This is a 1-cm thick percolation column on a west aspect at 10,100'. It suggests that over the last few days, the snow has warmed enough to start channeling melt water down into the lower snowpack. This will help stabilize the snowpack, but without overnight freezing, this water makes the snow weak and could lead to wet-slab avalanches.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    3

    Poor snowpack structure exists with consolidated slabs resting on buried persistent weak layers of loose, sugary, faceted snow on west through southeast aspects near and above treeline. The most dangerous areas are on slopes near and above treeline that face NW-N-SE where wind drifted snow has created slabs 1'-3' deep on top of these buried weak layers. These avalanches are becoming harder to trigger but once released, they will be large and destructive. Likely trigger points include shallower areas along slope margins, around sparse trees or rock outcroppings, or on repeat running slide paths.

    Yesterday, several extended column tests produced propagation (two did not) under hard loading steps near and above treeline on westerly aspects. (ECTP Hard x 4 and ECTX x 2). Consistent with the entire season, basal weak layers of facets and depth hoar comprised the weak layer of concern. I suspect this may be related to the relatively warm snow temperatures, where cold, stiff-snow produces more of a bridging effect, and warm/moist snow allows the weak layer to be more easily affected. In any event, although it feels like springtime, higher elevation shady slopes are still very much transition from the depths of winter and contain hard slabs on top of weak facets/depth hoar.

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1

    Strong southerly winds have created fresh deposits of wind drifted snow upper elevations. Look for fresh drifts on the leeward sides of ridge crests and terrain features like sub-ridges and gully walls. On steep, northerly aspects, wind drifted snow has added additional stress to buried persistent weak layers so it isn't merely a question of identifying and testing for wind slab instability. The bottom line is that steep, wind loaded, northerly-facing terrain is where you are most likely to trigger a deep and dangerous avalanche.

Special Announcement

The Geyser Pass Roadis down to the dirt on the lower third. The upper third is a sloppy slurry of mud and melted snow.

The Lower Utah Nordic Alliance (LUNA) groomed and set classic track into Gold Basin on Thursday. Traffic over the weekend has roughed up the surface.

Snow and Weather

24 Hour Snow T" 72 Hour Snow T" Base Depth in Gold Basin 46" Wind S 20-25 G40 Temp 29F

Southwest flow ahead of a strong low pressure system will bring increasing clouds, a high near 37 F (10,000'), and southwest winds ranging from 20-30 mph with gusts into the 50 mph range. Overnight temps remained warm and it barely froze at 10,000', making this the third night in a row without refreezing. Yesterday and overnight, southerly winds ranged from 25-50 mph. Looking towards the end of the week, the low pressure system is expected to make its way into the desert southwest bringing cooler and unsettled weather for the rest of the week starting tomorrow evening.

NWS Weather Forecast.

Wind, temperature, humidity on Pre Laurel Peak (11,700')

Snotel site near Geyser Pass Trailhead (9600')

Storm totals at the Gold Basin study plot (10,000')

Snowpack Discussion

Warm temperatures are promoting bonding and consolidating the snowpack, but without overnight refreezes, sunny, lower elevation areas contain weak snow. Avoid slopes that do not have a supportable crust and check for moist snow underneath thin crusts. Today with high clouds, we may see a bit of a greenhouse effect and many slopes will become dangerously weak, producing loose wet avalanches or possibly wet slab avalanches.

Strong winds have kept upper-elevation slopes cool, however, this is where you can find newly formed wind-drifts resting on fragile weak layers of faceted snow, primarily NW-N-E-SE.

General Announcements

This forecast is from the U.S. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.

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