Avalanche Advisory
Advisory: Logan Area Mountains Issued by Toby Weed for Saturday - January 9, 2016 - 6:48am
bottom line

MODERATE(Level 2): Increasing west winds at upper elevations could cause drifting and the danger to rise in the backcountry. Heightened wind slab avalanche conditions already exist on recently drifted slopes, and triggered deep slab avalanches failing on persistent weak layers remain possible in some areas. Avoid steep drifted slopes at upper elevations, evaluate the snow and terrain carefully, and continue to make conservative decisions.




current conditions

It's 17 degrees this morning at the 8400' Tony Grove Snotel. There's 48 inches of total snow, containing 94% of average water content for the date. The 9700' CSI Logan Peak weather station reports 10 degrees and fairly light northwest wind, averaging in the single digits and gusting into the teens. We've found the best riding in sheltered lower angled terrain. Sunny slopes have seen a few minor melts and refreezes, and many slopes sport a couple inches of heavier dust-on-crust. Off the wind damaged ridge-lines you can still find pretty good settled powder riding conditions in many areas.

With a few inches of fresh snow on the surface, any increase in wind this weekend will cause an increase in danger of wind slab avalanches. Small, and some larger wind slab avalanches have been common in the area in the first week of 2016, and you could trigger an avalanche this weekend on a steep slope with recent deposits of drifted snow. Time, compression, and settlement are gradually healing the instabilities in the snowpack, and dangerous deep slab avalanches continue to slowly become less likely in the backcountry. Even so, both our snowpit tests and triggered activity on New Years Eve indicate that you might still trigger large and scary avalanches in some areas.

Weak, sugary or faceted snow plagues the Logan Zone. The basal layers at upper elevations are gradualy strengthening under compression from the December slab, but the faceted snow at the bottom is still pretty weak. The entire snowpack is "rotten" at lower elevations. Faceted snow grains lack cohesion and failure in the basal layers can cause the entire snowpack on a slope to collapse and avalanche. (1-8-16)
recent activity
  • A rider triggered, was caught, carried, partially buried, and injurred on New Years Eve in a large and scary avalanche on a slope with a history of avalanche accidents in the Middle Fork of St. Charles Canyon. Video Report
  • On Monday, (1-4-16) in route to the St. Charles Avalanche, I observed several other recent sled triggered avalanches just north of the state line in the Danish Pass Area. In each case, the very broad 2-foot-deep avalanches failed on a thin layer of weak faceted snow on top of a rime or rain crust from December 8/9.
  • Observers reported natural and triggered wind slab avalanche activity on New Years Day and over the weekend in the Tony Grove and Providence Canyon Areas. The avalanches were fairly shallow, soft, and generally manageable, but we found solid chuncks from more recent fresh hard slab avalanches in the Providence Canyon Area on Wednesday, (1-6-16)
  • Evidence of significant natural activity from the productive pre-Christmas storm is widespread across the Logan Zone. Most of the natural avalanches occurred early in the storm, and likely failed and ran above the Dec.8/9 rime-crust. But, there are also a few that appear to be a bit more recent, released on deeper faceted weak layers, and a few might have been remote triggered...
  • DB Bowl Avalanche: Here's a video observation looking at a recent natural Avalanche in Logan Dry Canyon.
  • I observed several large more recent avalanches in the upper Providence Canyon area on 12/26. I think these were Christmas Eve naturals, but they might've been remote triggered, unseen by riders in limited visibility. Video Report
  • On 12/19 an experience local rider was caught and carried through trees, mostly buried, trapped, injurred, and rescued from an avalanche he triggered above the Tony Grove Campground. Video Report

***To view our updated list of backcountry observations and avalanche activity from around Utah, go to our observations page

Avalanche Problem 1
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

We may see an increase in westerly winds today. With a few inches of fresh snow in upper elevation fetch areas, if the winds do increase, so will the avalanche danger. Expect recently formed and developing wind slabs near ridge tops and in and around terrain features like gullies, sub-ridges, scoops, and rock outcroppings. Wind slabs may have formed on weak faceted or feathery snow that was previously on the snow surface, which means the slabs could be reactive to our weight, and they may stay sensitive to human triggering for a little while.

Avalanche Problem 2
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

Time, settlement, and sintering are helping to gradually stabilize the snow, and in many areas the slab layer is so thick that it would be very difficult for riders to trigger. But, dangerous avalanches remain possible in some areas, and heightened avalanche conditions persist. Dangerous deep slab avalanches might be triggered from shallower areas on the slab, especially in outlying drifted terrain at upper and mid-elevations.

***Pay close attention to signs of unstable snow like recent avalanches, whumpfing, and shooting cracks, and be willing to reevaluate your plans. In these conditions you might still trigger avalanches remotely, from a distance or worse, from below!

weather

It'll be mostly cloudy in the mountains, with a high temperature at 8500' of around 22 degrees and west winds around 15 mph along the ridges. It'll be partly cloudy tonight, with single digit temperatures and light southwest wind. A high pressure system will build into the region and persist though the first part of next week. Models are currently in disagreement as to the evolution of a low pressure that will effect the weather toward the end of the week.
general announcements

The CROWBAR backcountry ski race will be Saturday January 30. More info at http://CrowbarSkiRace.org.

Please submit snow and avalanche observations from your ventures in the backcountry HERE. You can call us at 801-524-5304 or email HERE, or include #utavy in your Instagram or Tweet us @UAClogan. To report avalanche activity in the Logan Area or to contact the local avalanche forecaster call me, Toby, at 435-757-7578. 

I'll update this advisory throughout the season on Monday, Wednesday, Friday, and Saturday mornings by about 7:30

This advisory is produced by the U.S.D.A. Forest Service, which is solely responsible for its content. It describes only general avalanche conditions and local variations always exist.