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RegisterMar 13th, 2019–Mar 14th, 2019
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Avalanche conditions will be improving Thursday. However, there are enough uncertainties to keep your radar on alert as you travel. Clouds are likely to limit Loose-Wet avalanches but even filtered sunshine and rising freezing levels may be enough. Watch for rollerballs or wet surface snow as signs of potential wet avalanches. Older wind slabs are gaining strength but avoid open slopes greater than 35 degrees showing obvious signs of recent wind drifted snow where you could still trigger an avalanche.
The only avalanches reported from the adjacent West-North zone Wednesday were small loose avalanches. Several natural loose wet avalanches occurred on steep sunny slopes, while human triggered loose dry avalanches occurred in very steep shaded terrain. The recent storm snow seems to be bonding well to the old snow interface. The strong March sun made quick work affecting the surface snow. Any slope that received sunshine Wednesday will show signs of a new surface crust.
Thursday’s avalanche forecast is a bit tricky. We expect overcast skies, however, it’s March, and the sun is strong. It won’t take many sun breaks, or thinner clouds to cause conditions to change quickly. Make frequent weather observations, be alert to changes in the weather that differ from the forecast, and be ready to alter your plans if observations don’t line-up with the forecast.
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.