Selkirk Mountains

The return of cool temperatures and snowfall to the mountains drive our avalanche problems today. New snow and wind from the west through southwest will continue to build wind slabs over a stout crust of refrozen snow on the leeward side of ridges and terrain features at upper and mid elevations. Look for new cornice growth, Styrofoam textured pillows of wind deposited snow and density changes in surface snow to give you a clue as to the distribution of wind affected snow. Cracking under foot and shooting cracks are tell-tale signs that you are approaching unstable snow. Avoid steep start zones and convex roll-overs where avalanches may run long distances on the stout and continuous bed surface.

This midweek mountain snowfall will add a welcomed soft layer on top of an otherwise hard crust on all aspects at above and near tree line elevation bands. However, this, along with moderate to strong winds, sets up a classic slab over crust avalanche layer cake. Warm, if not hot, temperatures last week and rain that saturated the upper snowpack has now refrozen into an approximately 15cm (6”) hard crust buried under new snow. The stout refrozen crust layer bridges weak layers deeper in the snowpack that have likely remained insulated from the below freezing temperatures. Be aware that wet snow problems could exist at lower elevation bands where temperatures may have remained above freezing. Deep boot penetration is a good indicator that the snow lacks cohesion and the potential consequences of wet loose avalanches should be on your mind.

Today winds from the west and southwest will continue to transport snow onto the north through southeast side of ridges and terrain features like gullies that already likely harbor wind slabs from yesterday. The continued transport of snow over the past 24hrs mean that wind slabs may be deeper than you would otherwise suspect and could run long distances on the stout crust layer on sustained slopes. As this weather pattern exists out of our area the wind direction will shift to the north. So keep your head on swivel if you plan to be out on Thursday because the distribution of wind sabs will change with the shifting wind.

Springtime is when many of us start to think about bigger objectives that we have been eyeing all winter as the snowpack consolidates and strengthens. However springtime brings wild shifts in weather that can change the avalanche hazard quickly. Being aware of how conditions are changing around you should inform your travel plans. With the return of cooler temperatures, our Wet Slab avalanche threat has lost its bite for the time being, but don’t put it completely out of your mind yet. The Wet Slab problem will come back into play this weekend when warm and sunny conditions return to our area and those buried instabilities are lubricated again by melt water. The main wetting front from last week's rain and HOT temperatures that made a weak, manky mess of the upper snowpack, while liquid water likely traveled deeper or to the ground. Places where water got hung up will likely refreeze during long periods of below freezing temperatures and lock up those instabilities. However, as we get deeper into April, the sun angle gets higher in the sky and this can have a profound influence on reemerging wet snow hazards - even thawing refrozen meltwater closer to the surface. Be wary of slopes with large glide cracks as the amount of water moving through the system could nudge these slopes closer to failure as the barrier between the ground and the entire snowpack gets lubricated like a slip-n-slide track. Glide avalanches are unpredictable at best to forecast.

The dueling battle of warm versus cold air enhanced by orographic lift when storms move through can lead to intense periods of snowfall, and rapid accumulations. Depending on the type of older snow surface the new snow falls on will have a big influence on bonding and how sensitive fresh slabs are. Use surface clues of unstable snow and non-consequential test slopes to set yourself up for success and identify areas of slopes to simply go around. Stepping into more complex or extreme terrain still requires cautious snowpack assessments and decision-making where even a small, more isolated slide can lead to a bad outcome.

**Eastern Oregon University is conducting a survey to better understand avalanche safety preparedness among motorized backcountry users. The survey will help us learn more about who is purchasing, and practicing with avalanche rescue gear (beacon, probe, shovel) and participating in avalanche education—and why some riders are not. The survey is confidential and anonymous. Your feedback is invaluable to improve avalanche education and awareness across North Idaho and Northwestern Montana. Please take a moment to share your experience and help your local avalanche community. You can take the survey HERE.**