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RegisterMar 10th, 2019–Mar 11th, 2019
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Expect increasing clouds, warming temperatures, and strong southwest winds on Monday ahead of an approaching frontal system. Watch for blowing snow and fresh drifts in leeward upper elevation terrain. You can trigger a slab avalanche on convex slopes and recently wind loaded features 35 degrees and steeper.
The weekend weather was gorgeous - sunny skies, calm winds, and highs in the mid-30s at the 5000ft level. The Mt. Baker/Hwy 542 areas experienced high use, and the recent snow was reactive to human traffic in specific areas. Several avalanches were triggered by skiers and riders on Friday and Saturday, while avalanche activity tapered off on Sunday. Avalanches failed on the old/new snow interface, breaking about one foot deep. Most avalanches were small (D1) and occurred in north facing, upper elevation terrain on convex rollovers steeper than 35 degrees. Two reported avalanches on Friday on Shuksan Arm were large enough to bury a person (D2) and broke 200ft wide and ran 500-1000ft downslope. The strong March sun caused small wet loose slides on solar aspects at all elevations. Loose dry sluffs were also triggered by skiers and riders and ran far and fast in steep shaded terrain.
A skier-triggered storm slab avalanche (D1.5) on Shuksan Arm, north aspect, 5200ft. 03/09/19 Adam U Photo.
March 10, 2019
February started stormy and cold with very active avalanche conditions on persistent weak layers. The month finished with continued cold temperatures but drier weather allowed avalanche activity to taper off. Persistent weak layers that were buried early in the month (Feb 8th) are now unreactive, though you can still find the grains.
Aside from the series of storms in early to mid-February, most regions have measured relatively light snow accumulation in the past 3 weeks. Snow has stayed soft especially on shaded slopes and faceting and surface hoar have been plentiful. While there has been plenty of sunshine since mid-February, very cold temperatures have kept melt-freeze crust to a minimum on sunny slopes.
A natural loose wet avalanche (D1.5) on a southeast aspect of Lichtenberg Mtn at 5,400ft. 3/10/2019. Photo: Josh Hirshberg
Recent Avalanches
Our attention shifted to the upper snowpack. Recent avalanche problems have largely focussed on wind transported snow and weak snow surfaces on both dry, shaded slopes and sun-exposed aspects. In some locations, a weak layer of surface hoar and facets was buried on March 6th. We’ll keep an eye on this interface as we move into the future.
A skier-triggered storm slab avalanche (D1.5) on Shuksan Arm, north aspect, 5200ft. 03/09/19 Adam U Photo.
Moving Forward
As we move further into March, there are two points to consider:
The strength of the March sun: As the sun creeps higher into the sky and the days grow longer, the sun can have a greater impact on the snow surface. When the sun comes out, expect things to change quickly. You may see avalanches conditions change with natural loose avalanches originating from sunny slopes, surface snow becoming thick and heavy, and slabs taking on a moist to wet snow character.
Weak surfaces: facets and surface hoar have blanketed snow surfaces in many zones. Any significant snowfall will bury well-developed and widespread persistent weak layers. Recently, most storms have not delivered enough precipitation to cause a problem.