Avalanche Forecast
Regions: Cascades - South West.
Three days of above freezing temperatures are driving big changes in the mountain snowpack. Be patient and let the mountains make this transition. Steer away from open steep open slopes and don’t linger in areas where avalanches can run and stop especially late in the day when natural avalanche activity may peak.
Discussion
Snow and Avalanche Discussion
This stretch of very warm weather continues Tuesday. After nearly six weeks of below average temperatures, daytime highs in the lowlands are breaking records. Thatâs a big change for the snowpack and itâs struggling to make the adjustment.
Avalanche observations continue to trickle in from around the region. Most reports have been natural and human triggered loose wet avalanches. Thatâs not a surprise with the recent warming. What is interesting are the few wet slab avalanches. Notably, a large wet slab avalanche was reported on NWACâs public observation page. Crystal Mt Ski Patrol also reported a few wet slabs triggered with explosives as part of their mitigation efforts. While none of these are widespread, they could be an early indication that wet slab conditions are developing.
During spring periods like this, plan for changing conditions. Slopes you travel on in the morning can be very different by mid-day. Be leery of traveling near or under cornices. They are experiencing the stress of this heat too and may fail without warning.
Snowpack Discussion
New Regional Synopsis Coming Soon
Avalanche Problems
Loose Wet
A quick look at the debris piles around the mountains may be all the reminder you need that this loose wet avalanche cycle is ongoing. As more water gets added to the snowpack Tuesday, these avalanches may grow larger, run father, and occur on shadier slopes. It won’t take long for the sun and warm temperatures to thaw a poor overnight refreeze of the snow surface. When this happens conditions will deteriorate quickly. Unless it’s frozen, you should consider any steep slope suspect. Avoid traveling on steep open slopes with wet surface snow, and be leery of traveling in areas where avalanches can run and stop.
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1
Wet Slabs
There are still several cold snow layers in the snowpacks of the West South. Another day of above freezing temperatures just means more water moving in the snowpack that can impact these layers. This may lead to an increase in wet slab avalanche activity. The problem is, wet slabs are notoriously hard to predict. The good news is, the solution can be simple. Give this snowpack time to adjust. Be suspicious of any open slope greater than 30 degrees and don’t linger in large avalanche terrain.
Release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slab avalanches can be very destructive.
Avoid terrain where and when you suspect Wet Slab avalanche activity. Give yourself a wide safety buffer to handle the uncertainty
A Wet Slab avalanche. In this avalanche, the meltwater pooled above a dusty layer of snow. Note all the smaller wet loose avalanches to either side.
Wet slabs occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoiding avalanche paths when you see pinwheels, roller balls, loose wet avalanches, and during rain-on-snow events.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1