Warm and windy weather today will keep a variety of potential avalanche problems on the list. Wind slabs will remain possible to human trigger at upper elevations, while above-freezing temperatures and the strong April Sun will create loose wet avalanche conditions at lower elevations. A few cornices have fallen since Friday, and some of those have triggered large to very large avalanches on the slopes below. We can't rule out the potential of another cornice falling today, so keep an eye on these potential overhead hazards.
Wind slabs that were created last Friday have become stubborn and more difficult to trigger. Overnight SW winds increased again and are now hovering in the 20 to 30 mph range on average at 12,000ft. Wind slabs will remain the most sensitive to human triggering where those winds are still finding some snow to transport onto the lee sides of terrain features.
An example of a recent slab in drifted terrain.
Wet Loose avalanches can be human-triggered or run naturally once the snow surface becomes moist and wet. In most cases, this avalanche problem will be small in size, but they will certainly have enough power to drag you down the slope our push you into more hazardous terrain. In rare occurrences, a small loose wet avalanche could pull out an old storm slab and propagate wider than expected. Stay away from terrain traps and consider overhead hazards once wet loose conditions develop. You can avoid the problem by moving to colder aspects or lower-angle terrain.
Wet loose avalanche activity that ran earlier this week. Similar activity is expected today.
Large, stubborn slabs several feet thick or more exist over faceted weak layers in the upper snowpack. Remote triggers and natural avalanches failing on these persistent weak layers have been gradually diminishing since widespread activity last week. The most recent persistent slabs have required larger triggers such as the mass of a smaller avalanche running through the terrain or a cornice falling. The greatest number of avalanches have occurred on easterly-facing slopes where faceted crusts exist. Similar structures exist on west-facing terrain. Recent warming on lower elevation and more southerly aspects has strengthened the upper snowpack with crusts, and triggering persistent slabs is less likely in that terrain. Weak layers on north-facing terrain are less developed and have been less active.
Early warning signs for this avalanche problem are rare and feedback is infrequent. You can reduce your chance of triggering this avalanche problem by avoiding recently wind-loaded terrain and unusually shallow terrain. Safer riding is where the snowpack is deep, wind-protected, and on slope angles less than 35 degrees, without steeper slopes above.
Very large persistent slab on the east face of Gothic Mountain. 3/31. This avalanche was likely triggered by a cornice falling onto the slope.
Yesterday's clear weather offered a great opportunity to observe recent avalanche activity after Friday's windy storm that deposited 1 to 2 feet of snow across the forecast area. Saturday's warm temperatures also produced loose wet avalanche activity, some falling cornices, and large slab avalanches.
Here are a few of the recent highlights from the observations tab: Sometime after 4pm on Friday 3/31, a very large avalanche ran off the East Face of Gothic Mountain and brushed one of the cabins in the townsite. This avalanche was likely triggered by a falling cornice. Two other large to very large persistent slabs were observed in the Beckwith Range. Another wide propagating slab was observed on a wind-loaded easterly-facing slope in Redwell Basin. Several other cornices have recently fallen. Late yesterday afternoon during the hottest part of the day a large storm slab was either remotely triggered or ran naturally above the Slate River Road.
Since Friday's storm, the snowpack saw its first shock of warm weather on Saturday. High temperatures at 11,000ft reached into the upper 30-degree range on Saturday. Similar avalanche conditions exist on Sunday, but avalanche activity will be slightly less likely now that the snowpack has seen that initial shock of warm weather.
