New snow and winds will keep avalanche danger considerable near and above treeline. Triggering small to large wind slab avalanches is likely near and above treeline. On north, northeast, and northwest slopes, these avalanches may then step down, triggering deep persistent slab avalanches that are very large and likely unsurvivable. Avoid wind loaded, rounded, pillowed, rippled, and corniced slopes steeper than 30° near and above treeline.
For less avalanche hazard, seek southerly and westerly slopes with no recent wind loading.
Near and above treeline, expect continued development of wind slabs on leeward slopes and terrain features. Avoid wind loaded, rounded, pillowed, rippled or corniced slopes, as these may have new sensitive wind slabs. Wind loading and small cornice releases were observed in treeless areas below treeline on Friday. Pockets of moderate avalanche danger may exist in areas below 10,000'.
The likelihood of a single backcountry traveler triggering an avalanche in deeply buried persistent weak-layers is probably unlikely, however the consequences will be high, with avalanches likely breaking wider, deeper, running further than expected, and possibly destroying trees that are 30-40 years old. However, it is possible for a traveler to trigger a wind slab avalanche that then steps down, triggering a deep persistent slab avalanche that is larger and likely unsurvivable.
North, northeast, and northwest slopes near and above treeline should be considered highly suspect and avoided, or travelled on with the utmost care and consideration. You are most likely to trigger these avalanches in areas with a shallower snowpack (< 1 meter) where the weight of a traveler can initiate propagation on the weak layer.
So far this season, four known natural persistent slab avalanches have occurred on ~northern and northeasterly slopes, with starting zones between ~11,000' and ~11,800'.
Sometime around January 16, an approximately 1.5m thick (possibly thicker) hard slab avalanche occurred in the Silverton Avalanche Path, a northeasterly slope of Fremont. See photo, and get more information here. Additionally, evidence of a second avalanche from the same storm cycle was reported in Jay's Slide (~northerly aspect). See photo. Both of these avalanches likely failed in depth hoar near the ground, similar to the HS-N-R3-D3-O avalanche on Fremont, during the New Year’s storm cycle.
Yellow arrow: Crown line in Silverton Path. Estimated at HS-N-R2-D2-U. Likely failed at depth hoar near the ground, and likely occured on MLK day, January 16, 2023.
Another avalanche was confirmed with field observations on January 19. Crown line (shown by black arrow) is just barely visible in this photo. Occurred in Jay's slide path, and estimated HS-N-R2-D2-U. Likely failed in depth hoar near the ground, on ~January 16.
January 18 photo by Troy Marino.
Based on observations on Wednesday and Thursday, at least four natural D2 avalanches occurred during the MLK storm cycle; https://kachinapeaks.org/Observations/#/view, and there were probably other avalanche occurrences. These all occurred on ~northerly and northeasterly aspects, near and above treeline. Keep this in mind as you plan your tour this weekend. Don't let all the powder and sunny blue sky cloud your good judgement.
For more information on the Avalanche Danger Scale, watch this video!
