As our previous storm settled out and high pressure sat in, recreationists have begun to push into the mountains skiing, riding, and observing the snowpack. As one forecaster put it, our snowpack has "more crusts than on a Thanksgiving day dessert table."  Several iterations of dry weather, rain events, and snow events have made our early season snowpack into a stack of faceted crusts.  While the crusts themselves don't pose a threat, once they get buried by a slab, it is time to take heed.  

A decent amount of snow fell last Tuesday snow totals ranging from 13 inches in the Whitefish Range to 6 inches by Marias Pass . While we received a handful of avalanche reports involving the new and windblown snow, the most significant avalanche reports came out of the upper elevations in Glacier National Park. Three very large (D3), persistant slab avalanches naturally occured with crowns 3-5 feet deep from high elevations. Check the report here.  On some of the uppermost, alpine locations, a thicker slab has been forming over mid-October weak layers without the stabilizing effect of our most recent rain event and subsequent crust.  

In the past few days of clear weather, the snow surface has deterioated and become weaker (See this observation and this observation).   Depending on your aspect and elevation,  surface hoar, near-surface facets, and sun crusts now blanket the snow surface. These layers don't immediately bond well to slabs: stay alert as new snow and winds come in over the next week.  As these winds crank up and snow accumulations increase over the weekend, we will have the snow available to transport to form fresh wind slabs. Signs of instability are snow blowing off ridgelines, cornice development, pillows, or shooting cracks. As snow begins to get moved around, it will be interesting to see how our persistant slab problem reacts with an additional load.  You can handle this uncertainty by reducing your exposure below alpine start zones and monitoring the structure of the snowpack.  If we see more snow than forecasted, watch for storm slabs to develop in wind protected terrain as well.  

This is an early season snowpack update. The FAC will continue to monitor conditions through the fall and post updates as conditions warrant. We anticipate daily forecasts and full operations to begin in December.