Bollettino valanghe

Provo

Utah Avalanche Center
Vedi sulla mappa

Pericolo valanghe

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco
Open full map
Non aggiornato — questo bollettino è scaduto 8 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

For today the avalanche danger is MODERATE at the upper elevations. Watch for fresh wind drifts on all aspects at the upper elevations. There also exists an isolated chance of triggering a larger avalanche breaking down near the ground in thinner snowpack areas above about 9500' on aspects facing northwest through east. Elsewhere the hazard is LOW.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    Westerly winds have increased since 7 PM Sunday, and you can expect to find fresh wind drifts at the upper elevations, especially above 10,000'. Although these drifts will be mostly on easterly aspects, cross-loading is possible on all aspects. Any fresh wind drifts your encounter are likely to be smaller pockets, however the excellent observation we received on Saturday from the UFO Bowls indicated sensitive wind drifts, where some drifts propagated 50' wide and running several hundred feet downslope.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    3

    We had hoped our persistent weak layer of weak, faceted snow down near the ground had settled down for a long winter's nap, but Saturday's Days Draw avalanche was a reminder that this problem still exists on very isolated slopes at the upper elevations, facing primarily north and northeast, but I also am suspicious about east as well. On slopes where the snowpack is deep (3-4'), this weak layer has adjusted to the load and the slab on top is strong. However, in thinner snowpack areas (1-3') this layer is still weak. The average depth of the Days Draw avalanche was 12-24".

    There are two reasons some slopes have a thinner snowpack: they avalanched previously (known as "repeaters") or they are in areas that have received less snow this month. The slope in Days Draw appeared to have been a repeater from late November. The photo below shows the snowpack structure of the crown on the Days Draw avalanche, where the very weak layer of faceted snow down near the ground is clearly visible.

    When I visited the Days Draw avalanche yesterday, I was expecting to find the northeast facing slope wind-loaded from recent westerly winds. But there was no wind loading. Other slopes that have this poor structure on a thin snowpack have likely been wind-loaded, adding additional stress to the weak layers below, and are just waiting for the unexpecting rider to hit the sweet spot.

    What to do? There were many tracks on the slopes adjacent to the Days Draw avalanche, so tracks are not an indication of stability. However we do know this weak structure exists on slopes with a snowpack less than about 3' deep on slopes facing north through northeast above about 9500'. Avoid these slopes and you avoid the problem.

Special Announcement

The new UAC IOS mobile app is now available on the app store. Check out the new "My Weather" feature.

Recent Activity

No avalanche activity was reported from the Provo mountains on Sunday. The most recent activity we have heard of was on Saturday in the UFO Bowls with fresh wind-loading on east aspect at 10,000'

Yesterday, my partner and I visited the avalanche in Days Draw (Avalanche Observation) that was triggered on Saturday December 22. This occurred in the Salt Lake area mountains. What was notable about this avalanche was that it failed on a layer of early-season facets, and had not been recently wind-loaded. This was on a NE-facing slope at 9900' in steep, rocky terrain with a thin snowpack. The crown averaged 12-24" and it propagated approximately 75'. More comments under avalanche problem #2 about how this avalanche occurrence relates to the current avalanche forecast.

Snow and Weather

Skies are overcast with light mountain snow showers. Overnight a trace to 3” of snow has fallen in the Provo mountains. South westerly winds have increased since Sunday evening, and are averaging in the teens with gusts in the 20’s and 30’s mph at the mid and upper elevations.

I guess we weren't as good as I thought we've been. We may pick up another trace to 2” of snow before partial clearing this afternoon. Winds will be westerly, averaging in the teens and 20’s mph, with gusts in the 30’s mph at the higher elevations. Winds are expected to diminish as the day progresses. Mountain temperatures will be in the 20’s F. We may pick up another trace to 2" overnight, and a few inches possible later on Christmas night. A chance for snow showers later this week, with colder temperatures.

General Announcements

CLICK HERE FOR MORE GENERAL INFO AND FAQ

This information does not apply to developed ski areas or highways where avalanche control is normally done. 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.

Regioni coperte