With strong south winds that pushed up valley last night, overall increasing temperatures today, and storm snowfall totals of 15-35″ the last three-days, an upside-down snowpack on the surface is very likely for human triggering. Increasing temperatures, precipitation (type/amount/rate) and winds (speed/direction) all are important factors contributing to the storm snow. Be attentive to this current problem that can change fast, look for red flag signs of instability, reactive, drifting or wet snow, cracking, whumphing, or natural avalanches. Identify and avoid avalanche slopes and run-out zones.
What we know, both zones up to 3000′ show poor structure (layers in the snow pack that could produce an avalanche) including melt-freeze crusts, buried surface hoar and near surface facets. It is best to assume spatial distribution is widespread until proven otherwise. Cold temperature gradients have weakening effects on these supportive crusts near the surface, they are possible for human triggering, especially in thin area near trees, rocks, cliffs and unsupported slopes. Probe the snowpack for this problem and feel for strong over weak layers, or a punchy, hollowness. Keep in mind this problem can be triggered from far distance/not on the slab and that additional weight/stress from recent snowfall, rain on snow, wind loading and warming temperatures all can increase the likelihood for triggering. (Click photo to learn more about surface hoar at avalanche.org)
Melt-freeze crusts in the snowpack act as a vapor barrier and are likely to exacerbate the presence of depth hoar and faceting (weakening of layers). Be aware of outliers and more snow/wind/rain/warmer temps adds weight and stress to the layers below. With a series of persistent layers in the mid-pack, the chances of an avalanche stepping-down are within the realm of possibility, however unlikely. Avoid big, open, wide 30° degree steep, exposed, planar, convex, or un-supported slopes, and especially terrain traps (cliffs, trees, rocks, gullies) or areas of drainage, where water could be flowing under the snowpack.
Bottom Line: The snowpack is complicated right now. So are our emotions with the community response to a natural disaster in our home and the taxed EMS resources are exhausted from the immediate and drawn out global pandemic. A range of freezing levels over the past two week & heavy precipitation coupled with variable spatial distribution of surface hoar/near surface facets (weak surface layers now buried) make it moderate to high confidant assessments difficult of what is really going on in the terrain.
Good News: It is still early in the season, a perfect time to self check human factors/decision bias. We need to respect outliers (the unexpected) as it already has been heavy year. Be patient, take breaks, stop and smell the roses, or enjoy the view and company. Stay vigilant about the changing conditions, evaluate the hazards, think risk vs. reward and remember if snow is the problem, terrain is the answer. Choose low consequence slopes and carefully identify terrain traps and areas to avoid.
Heavy snowfall mixed with rain over the last-three days saw temperatures rise from the low-teens to upper twenties and mid-thirties. Precipitation has tapered off with scattered rain and snow showers expected today. Temperatures remain above freezing near sea-level and up to 1,5000′. Strong south winds overnight are expected to diminish by tonight and become light to moderate from the East.
( *star means meteorological estimate )
It’s time to start thinking avalanche. Dust off your gear and make sure it is fully functional. Put new batteries in your beacons! Do a beacon practice to start the season and keep your skills fresh. If you head into the hills, watch out for avalanche conditions, and be especially careful of rocks and hidden hazards like crevasses beneath the snow. WEAR A HELMET!
Education Video Links:
Submit observations. Win prizes. Each snow, weather & avalanche observation outside of the HAC staff will be entered in a raffle drawing. The more observations, the more chances to win!
We have begun conditions updates for winter 2020/2021. Click the + Full Forecast link below for each zone to read more. Submit observations. Win prizes. Each snow, weather & avalanche observation outside of the HAC staff will be entered in a raffle drawing. The more observations, the more chances to win!
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