Southeasterly winds kicked up yesterday averaging 5-10 mph with gusts into the high teens. This may have formed very shallow, small wind slabs in leeward terrain. Hopefully the wind was enough to knock over/blow away some of the surface hoar in exposed terrain but that is probably wishful thinking. In anticipation of snow, we have been closely mapping the surface conditions as well as watching for new surface hoar growth. Surface hoar has been observed from valley bottoms to the Alpine and is resting on a variety of surfaces. There is a stout sun crust on southerly facing slopes. On shaded aspects 4-8″ or so of soft near surface facets sit over a firmer base. Along ridgelines and areas affected by the NW wind events there is hard sastrugi, wind crust and/or rime crust. This set-up does not bode well for bonding when then next loading event does occur and the surface hoar gets buried. Cloudy skies, light winds and a chance of snow today should not change the avalanche danger yet. However, watch for changing conditions if more snow falls than forecasted.
Today will be another day of Normal Caution (LOW danger). In addition to looking for mini wind slabs here are things to keep in mind if you are headed into the backcountry:
- Glide avalanches – These types of avalanches are highly unpredictable and not associated with human triggers. It’s always best to watch for and limit exposure under glide cracks.
- Dry-loose sluffs – Watch your sluff on steep shaded slopes.
- Cornice falls – As always, give cornices a wide berth.
- An outlier slab avalanche – Although it is unlikely a person could trigger a slab avalanche, the mountains can harbor surprises, especially in thin snowpack areas. South of Turnagain in the Summit Lake and Silvertip zones there is a shallow snowpack with a generally poor structure. A variety of old weak layers (facets and buried surface hoar) sit in the mid and base of the snowpack. The most suspect place to trigger an avalanche is steep terrain with old, hard wind slabs sitting on weak snow.
- Considering the consequences before entering into committing terrain and maintaining good travel protocol are good habits to keep on LOW danger days.
Surface hoar on a wind crust, Twin Peaks, 3-4-19.
Surface hoar at 1600′ on Tenderfoot, 3-1-19. Photo: Jacob Kayes
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