Northwest Mountains

Another foot of snow and transportable wind speeds are testing the snowpack again.  Destructive natural avalanches releasing from the alpine are a serious concern; avoid travel on or in the runouts of leeward start zones.  We have a dangerous setup of dense slabs several feet thick over a widespread weak layer.  On slopes that didn't recently avalanche, slabs are reactive to human triggers at all elevations.   Make conservative terrain choices to combat the threat of unusual behavior with our problematic buried weak layer under distress.  

The final pulse of snowfall this morning will bring current storm totals over a foot.  Snowfall totals over our January weak layer are about 50" at CBMR and 95" at Irwin.  The current snowfall and windloading will bring the snowpack back to, and potentially past, its breaking point in terrain that didn't recently avalanche.  The avalanche danger is straddling the high end of Considerable (Level 3) and low end of High (Level 4), with some uncertainty of how much natural activity will result today.  Given the already extensive cycle over the weekend and a relatively smaller loading event in comparison, I'm not expecting natural activity to be as widespread as what we've already documented.  However, some slopes will be at their natural breaking point today, especially windloaded terrain across our forecast area, or sheltered slopes in the shallow zone.  With an extra foot of snow in the past 24 hours, we're expecting conditions to be very sensitive to human triggers in parts of the Southeast Mountains, where this storm is both overproducing and a relatively bigger punch on the snowpack compared to total snowfall this month and this season.  An Avalanche Warning is in effect for the Southeast Mountains.   A forecaster in Cement Creek yesterday turned away from fieldwork objectives at the narrows due to constant booming collapses under a 3-foot slab.  The Northwest Mountains got hit by almost twice the water weight last week, so the snowpack is expected to hold up a bit better to the current loading.  We're showing High danger there in the alpine to cover some uncertainty; if paths start releasing again on windloaded slopes, they'll be up to D3 in size.  

Patience is the name of the game right now.  Our shallow and weak snowpack has been put through the ringer in the past week, and this is another hit.   With relatively quieter weather in the coming week, the danger will be on a decreasing trend after today.