In our last Avalanche Report, Ben talked about our third multi-day storm cycle of the winter. Since then, we’ve transitioned into an extended spell of high pressure, bringing fair weather and no new snow. Before we talk about how this weather pattern is changing the avalanche conditions, I want to take a moment and acknowledge the past month. It’s been nothing short of mind-blowing. The period from Dec. 11-Jan. 7 is the snowiest I can recall in my 17 years here. During this timeframe, we’ve had three separate multi-day storm events that each dropped 2-4 feet of snow. We’ve had additional “dribs and drabs” between these storm cycles. Back on Dec. 10, things were grim, and our snowpack was hovering around 60-80% of average. Moving forward, our snowpack jumped to 140-160% of normal in less than a month, which has made for great skiing, great for summer water needs and great for snow removal businesses. Everyone wins. So just how much snow did we get? Accurately measuring snowfall is tough during multi-day storm events. Remote weather station snow sensors measure both snow height gain (snowfall) and snow height loss (settlement). Both of these processes happen simultaneously during big storms—the major source of inaccuracy. One thing we can do is look at the amount of Snow Water Equivalent (SWE) that’s accumulated over a given timeframe. Most of our remote weather stations measure this accurately. First, what the heck is SWE (pronounced “swee” by snow nerds). If you put a bucket in your yard during a snowstorm, collected 10 inches of new snow, then brought it back indoors to melt—that would leave you the SWE. If it melted down to 1 inch of liquid water, that amount of SWE would mean the snow density is 10%. For reference: 4-5% snow is super fluffy powder, 8% is about average for our area, and over 10% is tending towards denser new snow. Using an average snow density and measured SWE, we can come up with an estimate of snowfall during the month-long period in question. For the calculations, I use an 8% average density, which seems reasonable (and likely conservative). Here is the estimated snowfall since Dec. 11 at a handful of local stations: Baldy—90 inches; Galena Summit—130 inches; Vienna Mine—180 inches. All this snowfall never gave our snowpack a break it needed. As weak layers deep in the snowpack received nearly continual loading, dangerous avalanche conditions resulted. It’s now been a week since the snowfall ended, and the snowpack is getting some much-needed rest. As a result, the avalanche danger has decreased, and we’ve begun to see more yellow and green in the avalanche forecast than orange or red. But low danger doesn’t mean no danger. Triggering avalanches is becoming unlikely, but not impossible. Be sure to read the finer details in the Daily Avalanche Forecast each time you head into the backcountry for a day of skiing or riding. Thanks for reading and enjoy the sunshine.(tncms-asset)85e6aac6-6e66-11ec-9679-fb49bcc2af2b(/tncms-asset)(tncms-asset)ae88d5a8-6e66-11ec-8713-cf8303142181(/tncms-asset)
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