The March sun can really pack a punch and destabilize the upper snowpack. Natural and human triggered avalanches remain likely.
Conservative travel habits and patience is key, especially when dealing with a persistent weak layer deeper in the the snowpack.
A persistent weak layer of facets on a crust exist 50 cm below the surface and has been touchy to human triggers, especially on northeast aspects at treeline (1700-1900 m). Remote triggering (from a distance away) is possible and a few size 2-2.5 avalanches failed easily on this layer Wednesday.
30 to 50 cm of recent storm snow has blanketed upper elevations. The likelihood of triggering a storm slab increases in steep or convex terrain and in wind loaded areas.
Looming cornices have grown large during the recent storm. They could pose threat from above and below, and weaken when the sun is out.
The warm spring sun may easily trigger loose wet avalanches at all elevations, especially on south facing slopes.
Change is in the air with a strong ridge set up through the weekend. This will bring clear and sunny skies, light northerly wind, and rising freezing levels.
Thursday Night: Some cloud cover with light northwest winds. Freezing levels dropping to 1000 m.
Friday/ Saturday: Mix of sun and cloud. Ridgetop wind light to moderate from the northeast and alpine temperatures near -4. Freezing levels (diurnal) 1000 m overnight and 1500 m during the day.
Sunday: Sunny skies with freezing levels rising to 2000 m during the day. Ridgetop wind moderate from the North and alpine temperatures possibly rising to 0 degrees.
No new avalanche observations by Thursday afternoon.
On Wednesday, a natural avalanche cycle up to size 3 was reported from the recent storm. A few skier controlled and remotely triggered (from as far away as 40 m) avalanches were also reported. These persistent slabs failed on the mid-February facet/ crust interface buried approximately 50 cm down. They caught people by surprise, but no involvements occurred.
30-50 cm of wind affected, storm snow sits over a variety of surfaces including sun crusts on solar aspects, a thick rain crust in windswept terrain and facets in shady, sheltered terrain. The recent storm snow has a decent bond in some areas, but a poor bond exists on northerly slopes (NW, N, NE, E) at treeline and in low alpine elevations (1700-2000 m) where the mid-February facet/ crust persistent weak layer has been touchy to skier triggers. Whumphing and remotely triggered avalanches have been failing on 3-5 cm of facets sliding on a hard melt-freeze crust. Some surfaces in windward alpine terrain have been scoured down to this firm crust.
Large and looming cornices have grown during the recent storm.
A crust/facet/surface hoar interface formed late-January is buried down 40-100 cm. This layer was most reactive between 1700 m and 2000 m. While this layer has been dormant in most of the region lately, large loads such as heavy snowfalls and cornice falls could wake it up and produce very large avalanches.
