Alpine temperatures dip back down to a more seasonal sub-zero in a brief cooling trend Friday. The sun will be shining so still keep an eye on those steep south-to-west slopes in the afternoon, as solar triggered loose snow avalanches are still possible.
Although the alpine air temperature isn't as warm as previous days, loose wet avalanches may still be observed on steep sun exposed slopes in the afternoon.
A crust sits near the base of the snowpack. Although we haven't had any reports of avalanche activity on this layer during the recent warming event, there is potential for large avalanches to be triggered on this layer by:
Thursday night: Partly cloudy, light northwest wind, temperature inversion dissipating, freezing level valley bottom.
Friday: Mix of sun and cloud, light northwest wind, freezing level valley bottom with strong temperature inversion re-establishing in the afternoon with above freezing air 2000-3000 m.
Saturday: Sunny, light southeast wind, strong temperature inversion with above freezing air 2000-3000 m.
Sunday: Sunny, light southeast wind, strong temperature inversion with above freezing air 2000-3000 m starting to break down.
Loose wet avalanches up to size 1.5 were reported on steep solar aspects during the warmup on Wednesday.
Our eyes and ears in the mountains are limited this winter due to fewer professional observations. If you go out in the mountains, please share your observations on the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!
Solar radiation coupled with a strong temperature inversion has formed a melt-freeze crust on solar aspects at treeline and above. Alpine surfaces are predominantly wind affected, with soft snow still to be found in shady, protected areas at lower elevations.
A couple of layers of feathery surface hoar crystals exist in the upper snowpack. Just 10 cm below the surface, the first of these layers has likely broken down in areas where the surface warmed up on Wednesday. Another patchier layer of smaller crystals may sit beneath 20-40 cm of old wind slab.
The lower snowpack is characterized by a couple of crusts, the most notable of which is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky areas in the alpine.
