Forecast for the Salt Lake Area Mountains

Issued by Drew Hardesty for Monday, December 17, 2018 - 6:14am
While most terrain has an overall LOW avalanche danger, isolated pockets of MODERATE DANGER exist for human triggered avalanches 2-4' deep into old snow layering. Heightened areas of concern include steep, thin, rocky terrain on northwest to easterly facing slopes. Collapsing and cracking may or may not be present to warn you of unstable avalanche conditions. Watch for any new wind slab development with today's increasing southerly winds.
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Weather and Snow
Splitter is a dirty word in this business. A Pacific storm system is splitting as it moves through and while our friends to the north and south pick up some snow, we'll be left holding the bag. At least we'll see a bump in winds. Currently, skies are partly cloudy with inverted temperatures in the mountains. Ridgeline temps are in the mid to upper 20s while the trailheads and basins are in the low 20s. Winds backed to the south and southeast overnight and are blowing 15-20mph with gusts to 30. We'll see increasing clouds and perhaps a trace or two by the afternoon. Soft settled powder exists in the mid-elevation glades, but sun and wind crusts dominate most of the landscape. Enjoy.
Check out the Weekly Review by Greg Gagne for a round up of weather and avalanche activity.
Recent Avalanches
Mark and Andrew found full propagation with snow tests on Argenta (Kessler Peak) in BCC yesterday and then immediately collapsed the snowpack and ripped a shooting crack (pic below) across the low angle slope. As if to confirm what they already knew. This from a north-northwest slope at 9000'. An outlier, but a reminder why we continue to assess each slope with an open mind and/or some suspicion. Other pros found full propagation in snow pits along the Brighton perimeter, but this seems less the norm as days wear on.
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Avalanche Problem #1
Persistent Weak Layer
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Description
Stabilization can be slow. Our old friend and colleague and now Colorado forecaster Jason Konigsberg delivered a presentation in Innsbruck Austria looking at the numbers of human triggered persistent slab avalanches after a loading event. In a nutshell, he found that 84% of the avalanches were triggered within three days of the event while 93% of the avalanches were triggered within 7 days of the loading event. His study involved data from 2011-2018 looking at just over 1800 avalanches. His excellent paper can be found on the Montana State University International Snow Science Workshop proceedings directory.
Photo: Heat map of all the avalanche activity from November 21st through December 16th. Notice how the bull's-eye terrain is upper elevation north and north east.
Additional Information
It's rare to see good decision-making in the news. On December 10th, pro observer Mark White, skinning up the famed Bonkers run in Broads Fork of BCC, bailed and turned around because he encountered snow structure that he didn't trust. (Observation) Live to ski another day. Right? But...the story doesn't end there. Three or four days later, a large avalanche came down, obliterating his tracks. (Observation) Was this a near-miss? A wise decision? Why or why not? I consider Mark White a friend and I am not unbiased. I appreciate his thought and consideration and ability to turn around in a situation where decisions have consequences. I also appreciate the communication and openness of the backcountry community to have these conversations. Talk about this on the drive up to the trailhead on while on the skintrack today. There's more here than meets the eye. Click on the photo to see before/after photos.
General Announcements
This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.

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