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Avalanche Forecast

Archived

Jan 7th, 2020–Jan 8th, 2020

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

Regions

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Natural avalanche should become isolated or end by early Wednesday as temperatures cool and precipitation relents, but dangerous avalanche conditions linger. A fresh storm slab sits on either a refreezing upper snowpack or adds to a 3-4 ft existing storm slab if you venture above 5500 ft. With uncertainty surrounding how quickly the snow will heal, and serious danger from slopes above, stay safe by avoiding open slopes steeper than 35 degrees.

Discussion

Take a moment to appreciate the magnitude of this event. Mt. Baker Pro Patrol reported widespread size 2-2.5 and even some size 3 avalanches ran naturally Monday and Tuesday, with numerous large avalanches also released by mitigation at the ski area. Significant features on Shuksan Arm, Hemispheres, and in Bagley Lakes all ran long distances.

Since the last rain crust formed at the end of the evening last Friday 01/03, Mt. Baker (Heather Meadows) added about 40” to their snowpack, before the snow changed to rain as the snow line crept up to 6000 ft on Tuesday. This addition of snowpack came with about 6” of water with two inches of rain received on Tuesday;  making for an impressive 13” of water equivalent since 4 AM on 12/31. The primary driver of the intense avalanche cycle was the volume of snow, but secondarily, the avalanches were more reactive because Monday’s low-density snow was rapidly loaded by an increasingly heavy slab. Rain ultimately completed the widespread cycle, changing the character of the avalanches. By Tuesday, the wet avalanches were gauging 3-4 ft deep through the entire volume of snow since last Friday.

Snowpack Discussion

New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.

Problems

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.