Problem #1: Storm Snow
Location: All aspects and elevations. Slopes 27 degrees and steeper. Storm totals are between 10-24" so far (highest amounts in the Transitional Zone), and around 4" additional is likely through the next 24-hours. Winds have been pretty light, which bodes well for quality of skiing. However, as you climb above 3000-4000ft keep an eye out for more wind effect from moderate south winds that were blowing at mid-levels above the inversion. Anywhere the new snow is wind loaded it will be slabby and prone to natural and human triggering. These storm slabs may be 30-90cm thick. Steep terrain will be actively flushing new snow through gullies. Avoid all terrain steeper than 30 degrees until this new snow has some time to settle. If you venture on to steeper slopes, watch carefully for any slabbyness or wind effect that could cause propagation across a slope. Carefully avoid convexities and any terrain traps.
Problem #2: Persistent Slab
Location: All wind-sheltered slopes. Areas of surface hoar formed around Dec.1st, and again on the 14th, mainly on wind-sheltered slopes (including sheltered high alpine bowls). These patchy but dangerous weak layers may be lurking between 20-80cm deep, depending on wind loading and exposure. The exact distribution of this dangerous weak layer is unkown, and the only way to find it will be to dig a shallow pit and shear off the new snow to carefully look for flat, shiny hoar crystals. That said, one snow pit may not be representative of a whole slope. Surface hoar layers are notoriously tricky to map out. It would be best to assume this layer exists on sheltered terrain (especially near treeline) and to assume it will be easy to trigger an avalanche on this layer. This is not a good time to be riding large or complex terrain. Wait until we have more data about this layer's distribution. Surface hoar layers do not bond over time, and must instead be crushed or flushed out by a major storm cycle. Use extra caution out there and please send in any observations.
Sporadic natural storm slab avalanches were observed from the last week, size D2-D3 on wind loaded lee aspects and gullies (above 3000ft). Crowns were around 60-90cm thick.
Light-moderate snow will continue to add up through Wednesday, with snow levels remaining at sea level.
( *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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