Avalanche hazard may seem to be improving under foot; however, be mindful that deep instabilities remain. Hurley and Birkenhead are the bulls-eye for a poor snowpack structure. Despite the MODERATE hazard rating, this problem is best managed through conservative terrain choices.
Watch for wind-affected areas where pockets of wind slab may linger.
Be aware that slab avalanches could step down to deeper layers producing larger-than-expected avalanches.
A widespread weakness from late December is found down 50 -70 cm. In some areas preserved surface hoar crystals sit on a crust; in some areas it's just a soft, weak, rotting layer in the mid-pack. This weak layer has been most reactive in the central and northern parts of the region, particularly around Hurley and Birkenhead .
No new avalanche reports Tuesday.
On Monday cornice chunks released slabby pockets in cliffy terrain below.
Last Saturday (4 or 5 days ago) Hurley was the bulls-eye for avalanche activity on persistent weak layers in the middle and bottom of the snowpack. Surface hoar on the Christmas crust was releasing naturally, intentionally, remotely, and with direct human triggers on gentle slopes near treeline (1800 to 1900 m) with crowns up to 80 cm thick. Some natural avalanches size 3 to 3.5 and ran full path from the alpine to valley bottom. Although not very recent, they remain instructive about what's portentially lurking in the snowpack's structure.
Thanks for the observations and please continue to post your reports and photos to the Mountain Information Network. It is really helpful for forecasters!
The region's generally weak snowpack structure remains.
Surface: At high elevationss here may be some lingering old wind slabs. At lower elevations last week's rain or wet snow has frozen into a crust.
Mid-pack: 50 to 70 cm below the surface is the late December weakness -- this appears to be the snowpack's primary critical layer. In some areas it's a crust and it's noteworthy that between 1900 and 1700 m surface hoar can be found above this crust which was reactive last week. This crust varies in thickness with terrain and elevation; in many places it's more of a soft-weak-rotting section of the snowpack.
Lower-pack: There is a widespread weak layer of facets and depth hoar at the bottom of the snowpack. Snowpack depths around treeline are about 150 cm deep.
Wednesday Night: Dry. Clearing. Cooling with alpine temps around -10 to -15 C. Light westerly wind.
Thursday: Dry. Mostly sunny. Alpine temps warming to around -10 C. Light westerly wind.
FridayDry. Mix of sun and clouds. Alpine temps around -5 to -10 C. Light westerly winds.
SaturdayIncoming weather bringing around 5 to maybe 10 cm of snow, moderate to strong southwest winds, and alpine temperatures around -5 C.
More details can be found in the Mountain Weather Forecast.
