Avalanche danger will increase in the afternoon as temperatures rise at upper elevations. Use extra caution where recent snow is experiencing sun and rapidly warming temperatures for the first time.
A sharp rise in temperature coupled with solar radiation on Tuesday afternoon, will promote rapid settlement and accelerated slab development in the recent storm snow. Be especially cautious where new snow may sit over a crust (south aspects) or surface hoar (wind sheltered areas around treeline).
A rapidly warming snow surface may release small loose wet avalanches, especially on steep sunny aspects. Pinwheeling is a good indicator of this type of instability.
Monday night: Clear, light northwest wind, freezing level 500 m.
Tuesday: Sunny, light northwest wind, freezing level 1000 m with an above freezing layer developing 1500-2500 m.
Wednesday: Sunny, light southeast wind, freezing level 3000 m.
Thursday: Increasing cloud, light south wind, freezing level 1000 m.
Natural, skier triggered and explosive triggered storm and wind slab avalanches were reported size 1.5-2.5 during and after the storm on Monday. Crown depths generally ranged 20-50 cm, with a 120 cm deep crown observed in a heavily wind loaded feature.
Tuesday we may see more storm slab avalanches due to rapidly warming temperatures and sun in the afternoon. They may be especially reactive where recent snow sits over a crust or surface hoar. Loose wet avalanches are also be possible, especially on steep solar aspects.
Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!
15-25 cm of recent snow sits over a thin melt-freeze crust on south aspects and surface hoar in wind sheltered areas around treeline. Fat pockets of wind loaded snow may be found in lee features at upper elevations.
The snowpack depth varies substantially with elevation. Below treeline 30 to 70 cm, 80 to 100 cm near treeline, and around 150 cm may be found in the alpine.
The mid to lower snowpack contains a series of crusts, the most notable of which is also the deepest, sitting 30 cm above the ground at elevations above 1500 m. This crust may have a thin overlying layer of weak faceted grains and/or surface hoar crystals, especially in sheltered areas around treeline. There is uncertainty as to whether these layer will be a concern going forward.
