Problem #1: Wind Slab
New snow from the 25th-26th (about 30cm deep above 3500ft) has had time to settle and bond, but it still sits on a layer of weak snow over an ice crust. This layer could still be reactive, especially in places where the wind deposited snow during the last storm and formed a harder slab on top of the weak snow. Look for slabs below cornices, near ridgelines and along lee slopes in gullies. Wind slabs are made of denser, wind affected snow and can sound hollow and/or drum like.
Problem #2: Storm Snow
Light snow flurries over the next few days will bring some much needed snow to the mountains, although the new snow will not bond well with the old snow surface. Look for signs of blowing snow that will indicate slab formation and use caution around areas where wind is depositing new snow. With only 1"-2" of snow forecast to fall, these avalanches will likely be small and shallow, although in steep terrain or near rocks, cliffs and gullies, the consequences of these avalanches could be high.
Above 3500ft, snow depths generally range from 30-130cm. In the deeper areas, we have a well-bonded midpack frozen solidly to the ground. It hasn't been terribly cold so far this year, so facetting between rain crusts has been minor so far. One exception is in high wind-swept areas where the snow is only about 30cm deep. In these areas, there are weak 2-3mm facets at the ground.
There was a widespread avalanche cycle on Nov. 26th, as the last storm warmed up bringing rain-on-snow up to 4500ft. D2-D3 Wet slabs occurred on all aspects above 3500ft. Crown depths were around 30cm, with the failure layer being weak/facetted snow sitting on our previous rain crust.
We had a very wet October and November, with snow levels about 1,000ft above average, near 3500ft. Above that level there was good accumulation, with almost nothing below it. December has started off with some drier and cooler weather although that should change beginning today.
( *star means meteorological estimate )
If you get out riding, please send in an observation!
Start the season with fresh batteries in your beacon, and do a rescue practice with your partners. Always carry a beacon, shovel, and probe, and KNOW HOW TO USE THEM.
Practice good risk management, which means only expose one person at a time to slopes 30 degrees and steeper, make group communication and unanimous decision making a priority, and choose your terrain wisely: eliminating unnecessary exposure and planning out your safe zones and escape routes.
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