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Avalanche Forecast

Archived

Nov 26th, 2012–Nov 27th, 2012

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Rockies.

This bulletin is based on a very small amount of stale data. Significant variations in conditions exist. Check out the Forecasters Blog for further details on interpreting early season bulletins.

Confidence

Poor - Due to limited field observations

Weather Forecast

Tuesday looks very similar to Monday.  Alpine temps should clock in at -7 with light SW winds.  The surface ridge that the region has been under breaks down beginning Wednesday.  Look for slightly warmer alpine temps on Wednesday along with a chance of precipitation in the afternoon.  I'm currently expecting 5 - 10 cm of snow late in the day Wednesday.  Thursday may deliver a bit more snow, check back for more details tomorrow. 

Avalanche Summary

There has also been a couple second hand reports of large whumphing in the Harvey pass area and triggering large size avalanche that could have run on the lower November crust.? If you and your friends have been out exploring and riding in the backcountry, and have some observations to share please send us an email to [email protected]. Lizard range info: Several Natural size 2.0 avalanches were reported on N-E aspects @ 1900m-2100m. Explosives control also produced size 1.5-2.0 avalanches on N aspects near the same elevation bands. These avalanches initiated in the current storm snow, and did not step down to deeper instabilities.

Snowpack Summary

Snowpack observations and information are extremely limited, and conditions across the region vary. In the alpine I suspect 100 + cm of snow, and treeline seeing an average around 90 cm. Storms slabs and wind slabs likely exist in alpine and treeline elevations. An early season (Nov 8) rain crust has been reported to exist around 2000 m and above on NW-NE aspects. I have no further information in regards to this crust, how deep its buried or reactive it may be. I do know that it has been a reactive sliding layer in other regions to the North, which makes me suspect this could be a problem also in the South Rockies. In the alpine I suspect 100 + cm of snow, and treeline seeing an average around 90 cm. Below treeline snow levels may just be reaching threshold.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.