Northwest Mountains

Warm temperatures today may keep the threat of large naturals breaking on weak layers near the ground ongoing in isolated areas.    Be extra cautious of traveling on or below steep, sunbaked slopes where the snow surface is getting moist, especially later in the day.   Avalanches can break wider and larger than you might expect.  On any aspect, sunny or shady, it is possible to trigger a deadly avalanche, especially in terrain where the snowpack is thinner and more variable in depth.  Continue to travel cautiously: buried weak layers have produced a number of very large avalanches this week in the Northwest Mountains.

Patience is a virtue.

The constant stream of large to very large persistent slabs continued yesterday.  We observed fresh slabs on Bellview (D3) and Whetstone (D2.5) that likely ran on Monday night from windloading.  Irwin explosively-triggered several large persistent slabs on the Upper Upper Westwall.  And yesterday afternoon, a smaller slab was triggered by warming on WSC Peak.   We've observed quite a few large persistent slabs releasing on the southern quadrant of the compass this week, a result of northwesterly winds.  With relatively warm temperatures last night into today, the potential for large, warming-related persistent slabs to release naturally exists on sunnier aspects.  These could be triggered by small wet loose avalanches or as the snow surface starts to get wet.    We're showing a higher danger rating in the Southeast Mountains, which have seen substantially more natural activity in the past week.  In the Northwest Mountains, we've seen more improvements in the snowpack structure and fewer persistent slabs.  However, the slabs that have released have been very large.   

Pronounced weak layers from our December and January dry spells have plagued us all season.  They are now buried 2 feet deep in the shallowest parts of our forecast area, and 6 feet deep or more in the deepest parts.  The persistent slab structure is ugly in the Southeast Mountains, and scary large in the Northwest Mountains.  Despite these poor structures, we are seeing diminishing signs of instability underfoot as we distance ourselves from the last major snowfall event and widespread cycle about a week ago.   Weak layers are deeper and harder to impact, and some slopes are starting to adjust.   As the danger starts to trend down, it is important to remember that the downtrend is because of the decreasing odds of an avalanche, not because the consequences have decreased.   In the game of Russian Roulette, there were 4 or 5 bullets in the chamber in early to mid-February. Now there are 1 or 2.  All bullets are equally deadly.   If you choose to ride avalanche terrain, careful snowpack assessments and terrain selection will reduce the odds of an avalanche even further.   Slopes that have recently shed their slabs offer safer options. Slopes with deep and uniform snow coverage offer lower-risk options. You can find more slopes that fit that description in the Northwest Mountains.  However, trigger points and weaknesses in the slab aren't always easy to identify (See this video from Whetstone yesterday).  The most tried and true way to remove all of the bullets from the chamber is on slopes less than 30 degrees that don't connect to steeper terrain above.