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. Uncertainty is best managed through conservative terrain choices.
Watch for wind-affected areas where deeper pockets of new or recent snow are cohesive and could react to human triggering.
Be aware that slab avalanches could step down to deeper layers producing larger-than-expected avalanches.
A widespread crust formed in late December is found down 50 -70 cm. In some areas preserved surface hoar crystals overlie this layer; 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 .
The snowpack structure, with its mid and basal problems, mean avalanche reports remain relevant, even if several days old.
On Monday cornice chunks released slabby pockets in cliffy terrain below.
On Saturday 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, intentiionally, 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.
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.
Last week's 20-30 cm of snow and southerly winds means wind slabs may linger. Below 1900 m there was a mix of rain and snow which is freezing into a crust.
Mid-pack: 50 to 70 cm down is a crust formed in late December -- this appears to be the snowpack's primary critical layer. 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.
Tuesday Night: South wind strengthens to moderate, strong at high elevations. Trace to 5 cm of new snow. Freezing level near 1000 m. Treeline temperatures around -5 C.
Wednesday: Moderate to strong southwest wind at high elevations, lessening to moderate in the afternoon. 5 to 10 cm of new snow. Freezing level 1000 m, briefly rising to near 1300 m late in the day. Overcast. Treeline temperatures around -5 C.
ThursdayMix sun and cloud. Dry. Cooler with treeline temps around -10 C. Light west wind.
FridayMix of sun and cloud. Dry. Treeline temps around -5 C. Light southwest wind.
More details can be found in the Mountain Weather Forecast.
