North aspects in sheltered areas are holding excellent snow, and stability has been good this week. Heavy snowfall Saturday night will raise the avalanche danger for Sunday.
Problem #1: Persistent Slab
We currently have two different persistent-slab dangers to watch out for: 1) old facet layers, and 2) buried surface hoar.
1) For the old-facets problem: Location: All aspects, at elevations above treeline where the snowpack is thin/windswept.
One concern is in areas of thin snowpack, where old facets (1-2mm) lurk underneath the wind slabs that sit at the top of the snowpack. We had reports of whumphing on these facet layers last week, showing that they are sensitive to human weight. This is mainly a concern in thin areas near rocks, and especially ridgelines. You can avoid this danger by sticking to areas of deep, uniform snowpack. Pole probing can help you map out which slopes contain hard-over-soft layering, a sign of this persistent slab danger. Remote triggering is possible, so keep track of your group and manage your exposure carefully.
2) For Buried Surface Hoar: Location: ALL elevations, clearings in the trees, and specific slopes above treeline (mainly slopes sheltered from NW winds) where surface hoar formed over the last 3-4 weeks and wasn't blown away by NW winds.
There are areas of buried surface hoar lingering at one and three layers down (roughly 20-60cm deep). These dangerous weak layers will persist for several weeks until they can be crushed and flushed out by lots of heavy snowfall. Be sure to dig around in wind sheltered areas to look for "the thin grey line" and clean shears. Assume this weak layer to be present in wind-sheltered areas. Use extra caution in openings around treeline, and avoid wind-sheltered rollovers in the alpine.
The last activity was from last week's warm period, when ample natural wet slides came down from steep, sun-blasted terrain. These loose-wet and wet-slabs were mostly size D2 and occurring in the early afternoon. There were a few skier-triggered persistent slabs in White Pass, which ran on old facets around 60-90cm deep. This shows that south aspects really woke up during the warm weather.
Feb. 25-28 was unusually warm. Temperatures spiked up to 46F at 4600ft, and stayed above freezing for 48+hours, causing a wet slide cycle. Since then it has been clear and cold with occasional moderate NW winds. A strong front will move in Saturday, with heavy snow Saturday night. 1-2" of SWE is expected by Sunday night(1-2ft of new snow above 1000ft) with snow levels rising to around 1000ft Sunday.
( *star means meteorological estimate )
If you get out riding, please send in an observation!
Do a rescue practice with your partners. Always carry a beacon, shovel, and probe, and KNOW HOW TO USE THEM.
Practice good risk management, which means only expose one person at a time to slopes 30 degrees and steeper, make group communication and unanimous decision making a priority, and choose your terrain wisely: eliminating unnecessary exposure and planning out your safe zones and escape routes.
Forgot your password?
Lost your password? Please enter your email address. You will receive mail with link to set new password.
Back to login