Bollettino valanghe

Moab

Utah Avalanche Center
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Pericolo valanghe

  • Alta quota
  • Limite del bosco
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Strong northerly winds have deposited stiff, shallow wind slabs on all aspects near and above treeline and a MODERATE avalanche danger exists on steep slopes that have recent deposits of wind drifted snow. The danger is greatest on steep slopes facing W-N-E-SE where recent slabs of wind drifted snow have increased the likelihood for human-triggered avalanches failing on a buried persistent weak layer. In these areas, human triggered avalanches a foot deep or more are possible.

An outlying possibility also exists for full depth avalanches failing on weak facets near the ground. Minimize this type of risk by avoiding thin slope margins and areas of rocky, radical, northerly facing terrain.

Many slopes have thin cover and rocks, stumps, and logs are lurking just beneath the surface.

Problemi valanghivi

  • Persistent Slabs

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

    Recent and wind-drifted snow has added additional stress to buried persistent weak layers increasing the likelihood of human-triggered avalanches in some locations. The danger is greatest on steep, wind-loaded, northerly aspects near treeline and above.

    A layer of near-surface facets (NSF) formed during the long December dry spell. This layer is now buried about a foot deep and has been sensitive in recent stability tests. It is especially reactive in areas where the wind has drifted enough snow to form a stiff slab on top. Human-triggered avalanches are most likely to fail here first and could be 1-3 feet deep in drifted areas. It is important to carefully analyze any slope you are considering by digging down to see if the poor structure exists. Avalanches triggered on this weak layer could also step down into our second faceted weak layer at the base of the snowpack. Avalanches failing on this layer would be deep, dangerous, and possibly un-survivable.

    In the video below, Dave Garcia demonstrates the reactive potential in our primary layer of concern.

    In our travels yesterday, Dave and I investigated a SE aspect at 11,600' where we continued to find the December drought layer as well as facets at the base of the snowpack. Stability tests produced no results but the adage that "structure trumps test results" keeps me leary of this kind of terrain. See the snowpit below.

  • Wind Slabs

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

    Strong winds blowing from the north on Wednesday and Thursday have built stiff slabs of wind drifted snow on all aspects near and above treeline, with even some shallow slabs found below. Slabs are becoming more reluctant to release but there is still enough evidence of cracking and collapsing for them to be a problem. Below are some tips for identifying and avoiding wind slabs. Avoid steep terrainn where you can detect recent deposits of wind drifted snow.

    • Wind slabs often form on the lee-side of exposed ridges and in and around terrain features. Watch for and avoid drifts on gully walls, under cliff-bands, along sub-ridges, and in scoops, saddles, and sinks.
    • Drifted snow is stiffer and more compacted than non-drifted snow, and hard drifts often produce hollow, drum-like sounds when you walk on them.
    • Freshly formed wind slabs can be quite sensitive and are often remotely triggered.
    • Shooting cracks in drifted snow are a sure sign of instability.

Special Announcement

Geyser Pass Road: Surface is mainly snowpacked and icy. AWD with good tires required.

Grooming Conditions: LUNA Matt groomed Geyser Pass with Gold Basin and set classic track yesterday.

Recent Activity

See the avalanche database here.

Snow and Weather

6 A.M. Snow and Weather Data

24 Hour Snow: T" 72 Hour Snow: 0" Season Total Snow: 58" Depth at Gold Basin: 28"

Winds on Pre-Laurel Peak: NA Temp: 24° F Percent of Normal (SWE): 96%

Weather

Skies are cloudy and it appears that trace amounts of snow have fallen as yet another storm tracks by to the north. Light to moderate westerly winds will shift to the north, and skies will gradually clear throughout the day. High temps will be in the mid teens. Overnight temps will crater into the low single digits. Sunday will be mostly sunny and cold. The upcoming week looks dry and cold with nothing in the long range models beyond.

General Conditions

Strong northerly winds Wednesday and Thursday have done a number on the snow surface and even sheltered, northerly facing terrain below treeline was not spared. Jake Etter toured up the Laurel Highway and down through the North Woods yesterday where he found lots of wind affected snow. He observed cracking in stiff shallow wind slabs and some isolated collapsing. Read his report here. Dave Garcia and I toured around on the east side of the range and found a veritable moonscape of wind affected snow. We found some soft snow below treeline but it was very hit and miss.

We continued to track the December drought layer of faceted snow that's about a foot below the surface and confirmed it's existence on upper elevation, SE aspects. We also found a lot of very weak snow in shady areas that in some cases was faceted through to the ground. There is a lot of spatial variability out there now made all the more complex by the recent wind event.

Below treeline snow conditions. Jake Etter photo.

Moonscape under the east face of Mount Mellenthin.

Snowpack and Weather Data

Snowpack Observations

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

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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.

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