Bollettino valanghe

Moab

Utah Avalanche Center
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Pericolo valanghe

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  • Limite del bosco
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In sintesi

A MODERATE danger existson all aspects above treeline where human triggered avalanches involving slabs of wind drifted snow are possible. Isolated drifts may also be found at lower elevations in wind exposed terrain. Be on the lookout for smooth, rounded deposits of wind drifted snow on the leeward sides of ridge crests and terrain features. Cracking is a sign of instability.

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. Most other terrain has generally LOW danger.

Problemi valanghivi

  • Wind Slabs

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

    Moderate NW winds and 5" of new snow Tuesday, has kept the threat of human triggered avalanches involving wind drifted snow alive on all aspects above treeline. Be on the lookout for unstable slabs of wind drifted snow on the leeward sides of ridge crests and terrain features such as gully walls and sub-ridges in wind affected terrain. Fresh drifts often have a smooth, rounded appearance and cracking is a sign of instability.

    Older drifts that formed over the last few days have stiffened up and are now mostly stuck in place, but steep slopes that have a smooth, rounded, "fat" appearance should still be approached with caution. 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 quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    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 last week's 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 the most recent 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

Geyser Pass Road update: Bulldozer work is expected to continue through Thursday with the road re-opening on Friday.

Recent Activity

No new avalanches have been reported since the one we observed last Thursday. For a complete list of avalanches see the La Sal Avalanche database here.

Snow and Weather

24 Hour Snow T" 72 Hour Snow 5" Season Total Snow 174" Base Depth at Gold Basin 80"

Winds on Pre Laurel Peak NW 15 G25 Temp 10

Weather

We remain under the influence of northwest flow. A weak shortwave brought trace amounts of snow to the mountains last night. Look for decreasing clouds this morning with clear skies later today. Northerly winds will blow in the 15-20 mph range with high temps at 10,000' in the low to mid teens. Thursday will be sunny and dry. No significant storms are in the near future.

General Conditions

5" of new snow on Tuesday provided a nice refresh and conditions remain quite good below treeline. Shifting winds over the past several days have blown and drifted snow on to all aspects above treeline. Be on the lookout for unstable slabs of wind drifted snow on the leeward sides of ridge crests and terrain features such as gully walls and sub-ridges in wind affected terrain. The November persistent weak layer (PWL) was given a significant load test last week. We observed one large avalanche that failed on the weak layer. The odds of triggering this kind of avalanche with the weight of a skier or rider are 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.

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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