Observation: Public

Observation Details

Signs of Unstable Snow

Observations

Given, the accessibility and above-average snowpack depth in areas known as the Methow Valley "Front Country," such as Elbow Coulee, I figured posting another observation here, for folks skiing on or under slope angles greater than 35 degrees, seemed appropriate. Especially given, the existing snowpack is mixed with past buried wind events, strong-warm and buried crust formations, and varied temperatures within the snowpack & between snowfalls which have led to the natural triggering of both dry and wet isolated slab releases with increasing size and debris as the winter moves along with the snowpack gaining dense integrity.

The snowpack throughout the Methow Valley UNDER (roughly) 3000 feet has undergone considerable and continuing alteration since the first substantial snowfall in early November, relating most significantly to air temperature persistence & variation, along with associated precipitations.

To recap, the snowpack events; There were early-season cold temp snowfalls, which never bonded well with each other or settled prior to the warming event. skiing slopes greater than 40 degrees caused a full snowpack collapse and sluff to the ground even throughout areas including vegetative anchors. Yet, the light, airy, cold, and therefore dry snow did not pose a kinetic energy value risk at that time. Then a multidirectional wind event scoured ridges and deposited dense slab deposits on various aspects, leading to quick-response natural releases (lower) Valley-wide. Following the slab events further natural releases triggered by snow falling from rocks or branches or other features showed considerable propagation (pyramid shape) tendency and again were not isolated to a specific aspect or elevation; however, did fail at the tera-surface contact point. Continued isolated snowpack failure events were noticed propagating to full track width and on less trap-defined slope terrain around rock formations with slope angles greater than 40 degrees, nearly a month and a half after the first sig. snows. At this point, Valley Wide rain and warming events provided a crust with density and thickness that has been able to trap upward thermal movement and reflect downward radiation back up into the snowfalls which have fallen since the crust formation. A second, less dense, thick, and cohesive crust then formed atop separate lightly bonded, varied temperature, snowfalls. Rain and snow mixed at times over a period of several days and were then capped by the most recent crust before temperatures fell consistently below zero again with daytime highs nearing, and for brief periods reaching and slightly exceeding the freezing level, with occasional, yet limited sun exposures softening a refreezing the uppermost layer. Finally, as of 1/22/23, there have been flurry snows and breezy ridgetop winds filling rounded crystals into micro concavities within slopes.

During the last prolonged warming event certain areas found East and West of Elbow Coulee, such as Jack Creek off of the Loup Loup Highway, and Wolf Creek West of Sun Mountain Lodge, roughly ten air miles apart, saw a fully rotted temperature gradient snowpack similar to spring snowpack, importantly unlike true spring conditions temperatures have since dropped and remained below freezing. This is important given the snowpack may appear to suggest spring snowpack conditions; however, REAL spring conditions include repetitious cycling of daytime thawing and nighttime freezing temperatures that enlarged crystal so dubbed "corn," within the snowpack. I mention this given the difference between spring-corn conditions and what exists, at least in Elbow Coulee for sure, makes traveling through aspects greater, than say, 35 degrees including road cutbacks worthy of exercising caution due to the potential of hanging, fairly consolidated snow like that which has recently released naturally in Elbow Coulee in multiple locations off rock features where the toe of the hanging snowpack was not supported allowing for the downward pressure to create a full release of the entire snowpack. Two of these releases were able to dislodge fire-killed down and standing trees of less than 8" in diameter with enough force to carry them to the final debris pile.

In a pit dug yesterday on a South aspect within Elbow Coulee roughly a thousand feet above the valley floor a significant layer of instability was seen, roughly fifteen centimeters or six inches below the surface. While the existing overall snowpack structure and shallow depth keep this upper layer from being considerably hazardous keeping it in check as potential future snows develop overtop🤞, may prove worthwhile.
Here's a link to a video of that 1/21 profile: https://youtu.be/t7LWB3K-374