Several loose wet avalanches were observed yesterday on E and S aspects in steep rocky terrain during the first major warming event to affect the snowpack in recent weeks. Most ares had a good solid refreeze overnight. Light winds may help keep the snow surface cool at upper elevations. That’s all good news for the likelihood of wet instabilities today. But as temperatures climb a few degrees warmer this afternoon loose wet avalanches will still be possible. By mid day on steep sunny slopes water saturated snow may result in wet sloughs. Even smaller and slow moving point releases can be hard to escape and can carry you into a dangerous situation, like a terrain trap. Time your day to be off of solar aspects before they get too warm. E aspects will warm first, then S, then W as the sun moves across the sky. Lower elevation northerly aspects may warm just enough for small loose wet avalanches where rocks and trees reflect the heat back down at the snowpack.
Persistent weak layers of sugary faceted grains in the snowpack continue to show potential for failure under stress. Going off of what little information we had, we have been concerned about sugar snow that was buried deeply by the recent storm on 3/1-3/4. Those areas where weak snow is buried over a meter below the surface seem to be trending less and less likely to result in an avalanche. However, snowpack tests continue to indicate the possibility for failure where facets are buried less than a meter deep. That’s concerning because at that relatively shallow depth an unlucky rider might still be able to trigger a large avalanche. Avalanches released from a rider’s tracks as recently at 3/8 near TJ Lake in Mammoth, so the problem isn’t going away yet. To hedge your bets, dig down and perform your own stability assessments if you intend to play on W-N-E aspects that had snow prior to 3/1, especially if brush and small trees that could act as anchors in the slab are sparse or covered over. It’s a good idea to know what these layers are doing before more snow comes later this week, adding more weight to the top of the snowpack.
In isolated areas where the slab above the facet layer will be warmed today, on E and W aspects, melt water may trickle into the sugary snow and weaken it further. Don’t play on slopes after they begin to show significant warming. Sinking deeply into wet snow and large rollerballs are good clues. Dig down and know what the snowpack looks like under your feet.