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 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The avalanche danger is MODERATE and human triggered avalanches involving slabs of wind drifted snow are possible on all aspects primarily above treeline. Isolated drifts may also be found at lower elevations in wind exposed terrain so keep your eyes out for smooth, rounded deposits of wind drifted snow.

On northerly aspects, a low probability/high consequence scenario remains for dangerous, human triggered avalanches failing on a buried persistent weak layer. Thinner snowpack areas, and areas of very steep, rocky, radical terrain are where you are most likely to find this problem.

Problemas de aludes

  • Wind Slabs

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

    With plenty of snow available for transport, moderate to strong ESE winds yesterday created fresh slabs of wind drifted snow on the leeward sides of ridge crests and terrain features in wind exposed terrain. Increasing northerly winds today will continue to blow and drift snow. Be on the lookout for fresh drifts on all aspects primarily above treeline, but also in any area exposed to the wind. Recognizable by their smooth, rounded appearance, wind drifts may also sound hollow underneath.

    Older drifts that formed mid-week will be covered up now, and though they have mostly stabilized, steep slopes that have a smooth, rounded, "fat" appearance should be approached with caution, especially on slopes with steep convexities. In very isolated, thinner snowpack areas, an avalanche triggered in the wind drifted snow could to step down to the November PWL causing a deeper and much more dangerous avalanche.

  • Persistent Slabs

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

    If you've been following along, you know that The November persistent weak layer (PWL) has been gaining strength and is deeply buried in most areas. Prior to this storm event, the last round of avalanches failing on this weak layer was during the New Years storm cycle. Before putting this problem to bed so to speak, we wanted to see what this latest load of heavy snowfall would do, and lo and behold, it produced a very large avalanche. Avalanche activity was not widespread, and stability tests indicate that the odds of a skier or rider triggering this kind of avalanche are unlikely, however it still may be possible in outlying areas that have a combination of radical terrain and a thinner, weaker snowpack, particularly on slopes facing the north side of the compass.

    Photo illustrates what is now a thin weak layer of faceted snow about a meter below the surface. The weak layer used to be much thicker, and then snow beneath was much weaker and looser. Time, and compressive weight from above has helped to strengthen this layer, but it was still capable of producing an avalanche under the stress of a rapid, heavy load.

    In most areas, the weak layer is deeply buried, and hence very difficult, if not impossible to affect by the weight of a skier or rider. The trick then, is to avoid areas where the snowpack is thinner such as in wind exposed terrain, along slope margins and near rocky outcrops, and in areas of very steep, rocky, radical terrain.

Special Announcement

Road Conditions: The road is plowed but it is extremely narrow with high banks, and much of it is one lane only. You may have to back up a significant distance if you encounter a vehicle from the opposite direction. Widening is scheduled for Monday.

Grooming: All trails were last groomed on Thursday.

Recent Activity

In our travels on Thursday we encountered a large avalanche (detailed in the video above) that failed on the November persistent weak layer sometime during this week's storm cycle.

This avalanche occurred on a steep northerly aspect near treeline in an area that has a thinner, weaker underlying snowpack. The starting zone is susceptible to heavy windloading and the terrain is fairly extreme with a steep convexity at the fracture line.

For a complete list of avalanches see the La Sal Avalanche database here.

Snow and Weather

24 Hour Snow 0" 72 Hour Snow 13" Season Total Snow 169" Base Depth at Gold Basin 80"

Winds on Pre Laurel Peak ESE 5-10 Temp 5

Weather

A rare day of sunny skies is on tap but it's going to be chilly up there. Temperatures are currently in the single digits with highs for the day creeping up into the low teens at 10,000'. Adding to the chill will be increasing northerly winds averaging 15-20 mph along ridge tops with higher gusts. Tomorrow look for increasing clouds ahead of a weak low pressure system that will again track through northern AZ into NM bringing us a chance for light snow Sunday night. A mostly dry, NW flow is setting up for the week

General Conditions

SNOTEL sites are not showing any new snow since yesterday, but I'm getting reports of several inches of new in isolated areas at upper elevations. All told, the mountains have received almost 3' of new snow this week. The new snow is settling out rapidly but conditions remain excellent in sheltered areas. Strong ESE winds yesterday drifted the abundant available snow on to leeward aspects. Slabs of wind drifted snow will less sensitive today but they still pose a threat, and steep slopes with recent deposits of wind drifted snow should be avoided. For more information see this observation from Nate Ament and Travis Nauman who were up getting the goods yesterday.

The November persistent weak layer (PWL) has just been given a significant load test and in our travels on Thursday we found an area where it failed producing a large, long running, un-survivable avalanche. The odds of triggering this kind of avalanche with the weight of a skier or rider are growing increasingly unlikely, however it still may be possible in outlying areas that have a combination of radical terrain and a thinner, weaker snowpack.

For more snowpack information see a complete list of observations here.

Snowpack and Weather Data

Gold Basin Storm Stake (10,000')

Gold Basin SNOTEL site (10,000')

SNOTEL site near Geyser Pass Winter Trailhead (9600')

Wind Station on Pre-Laurel Peak (11,400')

NWS forecast for the La Sal Mountains.

Additional Info

What's happening to the persistent weak layer? Salt Lake forecasters Nikki Champion and Dave Kelly discuss what has happened to it in the Wasatc Mountains. Down here in the La Sals we are trending toward this scenario.

General Announcements

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. This forecast will be updated by 7:30 tomorrow morning.

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