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Avalanche Forecast

Archived

Nov 25th, 2016–Nov 26th, 2016

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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Human triggered avalanches will become more likely above treeline in areas that experience significant wind loading. Storm slabs should be less sensitive on Saturday but use caution while navigating avalanche terrain and take it slow, the season is just beginning! 

Detailed Forecast

A warm front lifting north Friday night should bring light precipitation to the Cascades, except locally heavier near Mt. Baker through late Saturday morning.  Along with the precipitation, there should be a moderate warming trend even in the Cascade Passes through mid-day Saturday. 

Warmer temperatures and time will help the most recent snow settle and recent storm slabs should become less reactive to human triggering. Rain below treeline should have a limited effect on the avalanche danger due to the shallow snowpack and abundance of terrain anchors. The avalanche danger will be rated higher in the Mt. Baker area where heavier precipitation is expected. Expect the avalanche danger to be locally lower in the Cascade Passes were there is less snow and more terrain anchors. 

Wind slabs found above treeline should be the most sensitive avalanche problem on Saturday. Strong winds above crest level will transport snow to lee aspects, loading mainly NW through SE aspects.  

Use caution at lower elevations where creeks, rocks and other early season terrain hazards lurk just below the surface; your body and equipment will thank you!  

Snowpack Discussion

Mt. Baker was the hands down winner over the last 48 hours, with almost 4 feet of snow through Friday afternoon! Crystal, Chinook and Paradise also did quite well with 1-2 feet over the same time period. Lower storm totals were seen elsewhere including the Cascade Passes.  

Along the west slopes of the Cascades we heard from Crystal mountain pro-patrol today. Morning avalanche control work at Crystal produced widespread 8-10" storm slabs that released within the new storm snow. Storm slabs were the most sensitive in areas with the least wind effect. We also heard from the NPS ranger at Paradise that a skier triggered storm slab caught and carried a skier on a SE aspect of Mazama Bowl Friday afternoon. The shallow slab was about 10 cm (4") deep, 30 m across and ran 25 m vertically, failing within the storm snow. The skier went for a ride but was uninjured. We expect that in the Mt. Baker area where due to the higher storm totals, storms slabs were more reactive and deeper. 

Below treeline new snow has begun to cover terrain anchors and fill in creeks, though many areas need more snow to transform the landscape to full winter conditions. This particularly applies to the Cascade Passes where the snowdepth is still quite shallow.  

It's early season and the forecasts are based on limited field observations. Keep that fact in the forefront of your mind if entering avalanche terrain this weekend. 

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.