East Slopes South

Over 24 hours out from a major atmospheric river event, there's still a lot of running water in the snowpack. If you you don't have the support of firm crust on Thursday, then you are in snow capable of producing dangerous avalanches on steep slopes where you find wet, gloppy snow. Non-avalanche hazards remain a major risk, including firm icy slopes, downed trees, and blown out creeks with plenty of running water.

Bumping Ridge at 4600 ft added 5 inches to it's snowpack Monday and Monday evening before losing 8 inches to consolidation when the snow changed to heavy rain on late Monday night through Tuesday night. At higher elevations, Green Lake at 5900 ft added 8-14" of snow height before losing 7" to consolidation after the changeover to rain. With temperatures now at or exceeding 40 degrees up to 5900 ft, we expect that all elevations received rain and we're dealing with a wet upper (or perhaps entire) snowpack. Colder temperatures likely produced a supportable crust through much of the terrain.

Given our uncertainty regarding how the snowpack is handling the water and how quickly it will refreeze you'll be well served to continue to adopt an assessment mindset on Thursday as it still may be possible to find dangerous conditions. Pay careful attention for areas where the crust is not supportable or is breaking down with sunshine and milder temperatures.  It is in these locations where you could initiate larger avalanches deeper into the wet snow. Water will also be running to the base of the snowpack including smooth rock slabs. Cracks opening on slopes indicate that glide avalanches may fail at any time. Avoid traveling on or beneath smooth rock faces or steep convex rollovers where the slope may have a history of glide avalanches.

If you are traveling on southerly slopes, melt-freeze crusts formed prior to this storm cycle could form a bed surface for water percolating through the snowpack to pool and create a large and potentially widely breaking wet slab avalanche. We think these are unlikely at this point, but not out of the question. You can dig down approximately 1 ft in the snowpack and check for free water in the snowpack which may help identify whether conditions exist for wet slab instability.

When in doubt, travel on smaller terrain features, ridgelines, or forested areas to maintain a suitable margin of safety given the lower probability, higher consequence wet snow problems.

Shallow wind slabs may form due to up to several inches of fresh dry snow and moderate to strong W winds transporting these onto lee slopes. Steer around wind-loaded slopes and lens-shaped pillows where you might have 6" or more of dry snow over the gradually refreezing upper snowpack.

Non-avalanche hazards will be significant on Thursday:

• Firm and icy slopes have been reported in other forecast zones. Make sure you can self-arrest on the slopes you travel and consider bringing tools if you travel on steeper slopes.
• Creeks may be blown out, difficult to cross, and have high and fast-moving running water.
• Trailheads may be difficult to access due to downed trees, debris, and potentially flooding.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.